Idea to create a very high efficiency water heating system that is not in main stream that works on eddy currents.

Johncoool · 2025-01-14T08:56:23-0500

there are existing boilers that have a setup for sale. that work by heating a pipe using induction coil but also draw too much power.

ChatGPT · 2025-01-14T08:56:54-0500

Ah, now we’re talking about existing induction-based boilers—great point! These systems indeed heat pipes using induction coils, leveraging the same eddy current heating principles, but their inherent designs often demand significant power (which doesn’t align with the low-power, high-efficiency system you’re striving for). Let’s dissect why they’re power-hungry and design a solution to achieve your 1 Amp (240W) goal.

Why Existing Induction Boilers Draw High Power

Pipe Mass:
- Existing induction boilers often heat thick-walled stainless steel or other heavy metallic pipes. Heating such a large thermal mass (all at once) consumes a lot of power due to the specific heat capacity and size.
Continuous Heating Demand:
- Most boilers operate in on-demand mode, meaning they need to rapidly raise water temperature as it flows through the pipe. This requires high current to keep the pipe and water at operational temperatures.
Inefficient Design Trade-offs:
- The goal of many existing devices is speed, which sacrifices efficiency. A hotter pipe and faster water flow mean increased energy usage to close the gap between pipe temperature and water (since water has much higher thermal mass).
Non-scaled Induction Designs:
- Induction heating is often utilized at large scales (industrial boilers), where power and energy constraints are less of an issue—and they scale down inefficiently for home use.

How to Make a Low-Power Induction Boiler More Efficient

To design an induction boiler system that runs within 1 Amp at 240V (240W) for low energy usage while maintaining practicality, we need significant optimizations:

1. Smaller, High-Surface-Area Pipe Design

Use thin-walled metal pipes or thin plates in place of thick stainless steel.
For instance:
- A thin stainless steel pipe heats faster because less mass must reach temperature.
- Surface-to-volume ratio increases, improving heat transfer to water.
Example (Pipe Mass vs. Energy):
- A thick stainless steel pipe (~2 kg):
  - To heat from 20°C to 100°C:
    [
    Q = m \cdot C \cdot \Delta T
    ]
    Substituting:
    [
    Q = 2 \cdot 0.5 \cdot 80 = 80 \, \text{kJ}.
    ]
    At 1 Amp (240W):
    [
    t = \frac{Q}{P} = \frac{80,000}{240} \approx 333 \, \text{seconds} (\sim5.5 \, \text{minutes}).
    ]
- A thin-walled pipe (~0.5 kg):
  [
  Q = 0.5 \cdot 0.5 \cdot 80 = 20 \, \text{kJ}.
  ]
  Time for 1 Amp (240W):
  [
  t = \frac{20,000}{240} \approx 83 \, \text{seconds}.
  ]
  Key Insight: A thin-walled pipe can reduce heating time dramatically.

2. High Target Efficiency via Eddy Currents

Place the induction coil close to the pipe, minimizing the magnetic field gap.
Operate the induction coil at higher frequencies (~50–100 kHz) to optimize the skin effect (only heating the surface layer of the pipe).
This reduces heat loss and ensures heat energy is concentrated at the metal-water interface.

3. Low Flow Rate for Water

By slowing water flow through the heated pipe, you ensure higher temperature gains in a single pass instead of requiring continuous re-heating.
For instance, heating 1 liter per minute instead of 10 liters per minute shifts the system from high-power demand to low-power practicality.

4. Thermal Storage for Stability

Add an energy buffer (e.g., an insulated water tank or phase-change material system) to store excess heat during operation.
When demand is low, the coil’s 240W input can continue to preheat and store energy for later use, smoothing peak load demands.

Low-Power Induction Boiler Design Proposal

Key Components:

Thin-Walled Stainless Steel Tubing:
- Use a light steel pipe (e.g., 0.5–1 kg mass) with a high surface area and thin walls for rapid heating.
- Example dimensions:
  - Pipe diameter: 1 inch (~2.5 cm).
  - Wall thickness: 0.5–1 mm.
  - Length: 2 meters spiralized into a compact coil to fit compactly.
Induction Coil:
- Use a high-frequency induction heater running at 50–100 kHz.
- Wrap the coil tightly around the tubing to maximize energy transfer.
- Optimize design to minimize resistance losses.
Thermal Insulation:
- Encase the pipe in heat-resistant, insulated housing (e.g., ceramic enclosure) to minimize heat loss to the surrounding environment.
Low Flow Rate + Storage:
- Flow rate: 1–2 L/min.
- Hot water collects in an insulated buffer tank, allowing continuous low-power operation with stored energy capacity.

Calculated Performance

Heating 1 Liter of Water (Flowing Through Heated Pipe)

Heating water by 40°C (from 20°C to 60°C):
[
Q = m \cdot C \cdot \Delta T = 1 \cdot 4.186 \cdot 40 = 167.44 \, \text{kJ}.
]
At 240W input:
[
t = \frac{Q}{P} = \frac{167,440}{240} \approx 698 \, \text{seconds} (\sim11.6 \, \text{minutes}).
]
Flow rate considerations:
- With 1-liter batches, the system heats water to full temperature every 12 minutes, cycling per demand.

Why This Beats Traditional Induction Boilers

Energy Optimized for Low Power:
- Unlike existing induction boilers, this system uses lighter materials and slower water flows to reduce instantaneous power demands.
Long-Term Cost Efficiency:
- No need for high power peaks (e.g., 3+ kW), meaning it operates seamlessly on limited grids or renewable energy systems.
Scalable:
- With added thermal storage and flow rate customization, the system could scale up for larger households or multiple heating zones.

Final Thoughts

Existing induction boilers often sacrifice efficiency for speed due to their industrial roots. By leveraging small-scale, low mass designs, slow flow rates, and targeted thermal storage, we can create a 240W induction boiler that’s highly optimized for home use. If you'd like, we can refine this with specific dimensions or adjust design elements further.

Johncoool · 2025-01-14T11:26:08-0500

200 watts or 1 amp at 240v to heat up one pipe with circulation pump that is on 24/7. will it heat up the home

ChatGPT · 2025-01-14T11:26:29-0500

Ah, now we’re talking about using 200 watts (1 amp at 240V) to heat one induction pipe with a circulation pump running 24/7 for home heating. Let’s objectively evaluate if this setup can work to heat an entire home, and what constraints we’re working with.

Key Assumptions

Power Budget:
- 200W continuous input power (1 Amp at 240V).
Pipe Setup:
- The induction setup heats a single pipe that’s incorporated into a circulating system.
- Let’s assume the metal pipe is constructed for optimal eddy current heating (thin-walled stainless steel or aluminum).
Circulation:
- A circulation pump transfers water heated by the induction pipe into radiators, under-floor heating, or another heat emission system.
Required Heating for Home:
- Let’s assume the average heating demand for a small, reasonably insulated home is around 3 kW of thermal energy per hour to maintain warm temperatures (this number adjusts based on climate and insulation quality).

The question is whether 200W of sustained input can generate enough energy to maintain comfortable home heating.

Energy Analysis

Step 1: Calculate Total Energy Output in 24 Hours

With 200W input running continuously:
[
\text{Energy Output per Hour} = P \cdot t = 200 \, \text{W} \cdot 1 \, \text{hour} = 200 \, \text{Wh}.
]
In 24 hours:
[
\text{Total Energy Output} = 200 \, \text{Wh} \cdot 24 = 4,800 \, \text{Wh} \, (\text{or } 4.8 \, \text{kWh}).
]

Step 2: Compare with Home Energy Requirements

A typical small home in a cold climate might require 3 kW of heating per hour. In 24 hours, this comes out to:
[
\text{Heating Demand per Day} = 3 \, \text{kW} \cdot 24 = 72 \, \text{kWh}.
]
Now compare:

Your system provides 4.8 kWh/day.
The home needs 72 kWh/day.

Clearly, 200W is not enough to heat an entire home directly.

How to Improve Efficiency

Rather than abandoning the idea outright, we can optimize the design to make the most of the available 200W:

1. Insulated Thermal Storage (Slow and Stored Heating)

Instead of relying on continuous heating during peak demand, focus on running the 200W system continuously to slowly heat a thermal reservoir (e.g., an insulated water tank or phase-change material).
Store the generated heat when it’s not immediately needed.

For example:

If you heat 200 liters of water in a highly insulated tank, you can generate:
[
Q = P \cdot t = 200 \, \text{W} \cdot 24 \, \text{hours} = 4,800 \, \text{kWh}.
]
Over 24 hours, the entire tank will warm to usable temperatures for short bursts of high-demand heating (e.g., running radiators or pumps during specific hours).

2. Increase Radiator Effectiveness

With only 200W of input power, surface area matters. Use large, conductive radiators (or under-floor systems) to maximize heat transfer to the room using low-grade heat.

3. Improve House Insulation

If your home requires 72 kWh/day, there’s more energy leaking out than you can feasibly provide with 200W. Minimize these losses by improving insulation (e.g., double glazing, heat-reflective sheeting).

4. Zone-Based Heating

Limit heating to a single zone/room (e.g., living room or bedroom).
Heating just one or two rooms at a time drastically reduces energy needs.

Reality Check: Can This Heat a Home?

No, 200W won’t heat an entire home in most climates—not even close on its own. However, with optimized usage, it can:

Heat very small areas, like a single insulated room.
Supplement other heating systems.
Serve as a thermal reservoir charging system for specific time-based heating.

Let me know if you'd like numbers refined further or suggestions on alternate approaches!

Johncoool · 2025-01-14T11:33:24-0500

work backwards, what temp will the pipe reach at 200w of eddy currents? i saw rods that reach over 500c with less power.

ChatGPT · 2025-01-14T11:34:02-0500

Ah, now we’re flipping the analysis and working backwards—determining the pipe’s temperature when exposed to 200W of continuous power through eddy currents. If you've seen rods reaching 500°C with less power, there’s clearly a role being played by power density, material properties, and heat loss management, all of which I’ll factor into this model.
Let’s dive into it step by step:

Key Factors That Impact Temperature of the Pipe

Power Input:
- 200W of continuous power applied as a focused magnetic field via eddy currents.
Thermal Loss Management:
- Heat loss to the environment (convection and radiation) slows down how much energy the pipe retains, impacting the maximum temperature it can reach.
Material Properties:
- Conductive metal (such as aluminum or steel) will determine:
  - How quickly heat distributes in the pipe.
  - Heat retention capacity and thermal equilibrium.
Surface-to-Volume Ratio (Power Density):
- A small, thin rod or plate has less mass, which means more power per unit of material—achieving rapid temperature gain.
- Larger, bulkier surfaces spread the same power over more mass, leading to lower temperatures.

Step 1: Get the Basics – Energy Flow

How Much Energy Will the Pipe Gain?

To calculate the rise in temperature, let’s use the fundamental equation for thermal energy:
[
Q = m \cdot C \cdot \Delta T
]
Where:

( Q ): Energy supplied (in Joules).
( m ): Pipe mass (in kilograms).
( C ): Specific heat capacity of the material.
( \Delta T ): Temperature change.

For 200W power over time:
[
Q = P \cdot t
]
So, the time to hit certain temperatures depends on the mass of the pipe, the type of material, and how quickly heat escapes.

Step 2: Let’s Work the Numbers

Case 1: You’re Using Aluminum for the Pipe

Mass of the Pipe (( m )): Let’s assume a small, lightweight aluminum tube with a mass of 0.5 kg (approx. 1-meter length, thin-walled design).
Specific Heat Capacity (( C )): Aluminum's specific heat ( = 0.91 \, \text{kJ/kg·°C} = 910 \, \text{J/kg·°C} ).

At 200W input, how much time will it take to raise the pipe to 500°C (from 20°C)?

Energy Required:
[
Q = m \cdot C \cdot \Delta T
]
Substituting values:
[
Q = 0.5 \cdot 910 \cdot (500 - 20)
]
[
Q = 0.5 \cdot 910 \cdot 480 = 218,400 \, \text{J}.
]
Time to Reach 500°C With 200W Input:
[
t = \frac{Q}{P} = \frac{218,400 \, \text{J}}{200 \, \text{W}}
]
[
t = 1,092 \, \text{seconds} = 18.2 \, \text{minutes}.
]

Case 2: What About Stainless Steel?

Mass of Pipe (( m )): Let’s stick with 0.5 kg.
Specific Heat Capacity (( C )): Stainless steel's specific heat ( = 0.5 \, \text{kJ/kg·°C} = 500 \, \text{J/kg·°C} ).

Energy Required:
[
Q = m \cdot C \cdot \Delta T
]
Substituting values:
[
Q = 0.5 \cdot 500 \cdot 480 = 120,000 \, \text{J}.
]
Time to Reach 500°C With 200W Input:
[
t = \frac{Q}{P} = \frac{120,000}{200}
]
[
t = 600 \, \text{seconds} = 10 \, \text{minutes}.
]

Case 3: Lightweight Rod (Minimal Mass)

If using a small stainless steel rod with a lower mass (( m = 0.2 \, \text{kg} ), for example):

Energy Needed:
[
Q = 0.2 \cdot 500 \cdot 480 = 48,000 \, \text{J}.
]
Time to Glow (200W Input):
[
t = \frac{Q}{P} = \frac{48,000}{200}
]
[
t = 240 \, \text{seconds} = 4 \, \text{minutes}.
]

Step 3: Assess Temperatures at Equilibrium

Given infinite time, the temperature could theoretically rise indefinitely if no energy escaped. But here’s the kicker: thermal losses (radiation and convection keep temperatures capped at a practical maximum. Let’s calculate equilibrium:

Thermal Loss Through Radiation:
At high temperatures, heat is lost via blackbody radiation. Using:
[
P{\text{loss}} = A \cdot \sigma \cdot \epsilon \cdot (T^4 - T{\text{ambient}}^4)
]
- ( A ): Surface area of the pipe.
- ( \sigma = 5.67 \times 10^{-8} \, \text{W/m}^2\text{K}^4 ): Stefan-Boltzmann constant.
- ( \epsilon ): Material emissivity (e.g., stainless steel = ~0.1).
- ( T ): Surface temperature (K).
- ( T_{\text{ambient}} ): Ambient temp (K).
When ( P_{\text{loss}} = 200\, \text{W} ), equilibrium is reached.
For thin lightweight pipes, losses set an upper limit on max achievable temperature.

Why Do Rods Glow with Less Power?

You mentioned glowing rods at 500°C with less power—this can happen when:

Lightweight Mass: The rods have minimal material to heat (e.g., 0.1–0.2 kg).
Lower Heat Loss: Small rods radiate and lose less heat compared to larger pipes, reaching higher temps faster.

In those cases, power density (W/m³) is maximized, allowing faster and hotter heating.

Final Answer

For a 200W system heating a 0.5 kg pipe:
- Stainless steel reaches ~500°C in ~10 minutes.
- Aluminum reaches ~500°C in ~18 minutes.
Practical Equilibrium Temp:
- Due to heat losses, the pipe’s steady-state temp will likely stabilize lower (300–400°C) unless insulated or small mass/area ratio helps minimize losses.

If we design around your pipe/coil specifics, I can refine further and include losses or conditions like air convection!

Johncoool · 2025-01-14T11:35:00-0500

ok now consider that on 24/7 how house heating.

ChatGPT · 2025-01-14T11:35:23-0500

Now that we’ve determined a pipe heated by 200W eddy currents can reach a high temperature (~300–500°C, depending on material and losses), let’s analyze how that applies to heating a home when the system runs 24/7. This will involve determining heat transfer efficiency to the home (via radiators, air, or water circulation) and whether the sustained 200W input can come close to matching a typical home’s heating requirement.

1. Heat Transfer Systems

Let’s assume the hot pipe (via eddy currents) is part of:

Water Circulation: Heating circulating water (e.g., for radiators or underfloor heating).
Air Circulation: Heating air directly by conduction/radiation, spreading warmth via ducts or blowers.
Radiation: Directly emitting infrared heat into the home.

Each system transfers heat differently, and we’ll analyze how much usable heat can be delivered over 24/7 operation.

2. Total Heat Energy Delivered in 24 Hours

From the previous calculations:

The system provides 200W of continuous input.
Over 24 hours:
[
Q = P \cdot t
]
[
Q = 200 \, \text{W} \cdot 24 \, \text{hours} = 4,800 \, \text{Wh} \, (\text{or } 4.8 \, \text{kWh}).
]

This is the absolute maximum available energy to heat your house.

3. Is 4.8 kWh/day Enough for Home Heating?

Typical Heating Requirements:

A small, well-insulated home in moderate climates (10°C outside to maintain 20°C inside) might need:
- 1–3 kW/hour of heating power, depending on insulation, window efficiency, and outside temperature.
Over 24 hours:
- 24–72 kWh/day would typically be required.

Comparison:

Your system provides 4.8 kWh/day.
Even the lowest heating demand (24 kWh/day) is 5 times higher than what your 200W system can deliver.

So, 200W alone cannot heat an entire house unless the heating requirements are drastically reduced or the heating is localized.

4. Making 200W Useful for Heating

Since 200W isn’t enough for whole-home heating, we need to optimize the design to get maximum benefits:

Localized Heating (Single Room Approach)

Instead of heating the whole house, target one room:

Room Size:
- A well-insulated room (10–15 m²) could need ~200–500 W of heating power.
Performance:
- If your 200W system is paired with:
  - A small, enclosed room.
  - Efficient heat transfer (insulated radiators, strategic placement).
- You could potentially keep the room warm around 18–20°C.

Energy Storage for Timed Heating

If direct heating is insufficient, use thermal storage:

Buffer Tank Design:
- Use the hot pipe to heat water in an insulated buffer tank running through the day.
- Stored heat can be released during high-demand hours, supplementing the low-power input.
- Example: Heating 200 liters of water to 60°C stores:
  [
  Q = m \cdot C \cdot \Delta T
  ]
  [
  Q = 200 \cdot 4.186 \cdot 40 = 33,488 \, \text{kJ} (\sim9.3 \, \text{kWh}).
  ]
- Even with some heat loss, this doubles your effective heating capacity during usage spikes.

Increase Heat Transfer Efficiency

Maximize the use of the 200W system by:

Maximizing Surface Area:
- Replace a thick pipe with thin, wide fins or plates to improve conduction/radiation efficiency.
- For example:
  - A narrow pipe might radiate 10% of its heat to the room.
  - A wide, finned radiator might transfer 70–90%, making better use of the input energy.
Heat Circulating Air Directly:
- Surround the heated pipe with low-flow ducted air, allowing the heat to spread faster into adjacent areas (room or hallway).

Combination System

Use the 200W system as:

A supplement to existing heating systems (reducing overall energy demand).
A permanent heat source for select zones (e.g., bedrooms, bathrooms).
A water heating system that pre-warms radiators, storing and recycling heat.

5. Real-World Example Comparison

Rod Heating with <200W:

You noted induction rods hitting 500°C or more with less than 200W.
These rods likely rely on direct radiation (infrared heat) to warm an immediate area.

Using this principle:

If the pipe is maintained at 300–500°C, radiating directly into a living space:
- A small heat radiator might emit ~100–150W usable heat into a room.
In a very small, enclosed space (~10m²), this level of heat could maintain acceptable warmth (16–18°C).

Scaling for Larger Homes:

Even with optimized radiation, convection, and circulation, 200W cannot heat an entire home year-round. This approach is best suited for localized heating or as a complement to other systems.

Summary

Can 200W on 24/7 heat a home?

Not the whole home. At best, it can support localized heating in small, insulated spaces or supplement energy-efficient zones.

How to maximize the 200W system?

Target individual rooms or areas instead of the whole home.
Use thermal storage (e.g., water tanks) to capture heat over time for later use.
Implement high-efficiency heat transfer methods (thin pipes, large fins, ducted air circulation).

If you'd like, I can refine these calculations further based on specific room sizes or conditions you’re working with!

Johncoool · 2025-01-14T11:37:59-0500

Ah, with a 30 Amp max limit at 240V AC, we open up much more practical possibilities for your eddy current-powered, high-efficiency water heating system. Let's calculate the feasibility and refine the system to make sure it comfortably fits within this power ceiling while achieving the "flash heating" concept you've envisioned.
1. Determine Power Budget
Using ( P = V \cdot I ):
[
P = 240 \cdot 30 = 7,200 \, \text{W} \, \text{(7.2 kW max input power)}.
]
This is now a solid upper limit for the system. At 7.2 kW, we’re still within a realistic range for household setups and induction applications while maintaining quick operation. Let’s rework the heating setup to fit this budget.
2. Energy Required to Flash Heat 10 kg Aluminum
From earlier calculations:
To heat 10 kg of aluminum from 20°C to 100°C:
[
Q = m \cdot C \cdot \Delta T
]
Substituting:
[
Q = 10 \cdot 0.91 \cdot 80 = 728 \, \text{kJ} \, (\text{or } 728,000 \, \text{J}).
]
Time to heat with 7.2 kW input power:
Use ( P = Q / t ) to calculate time:
[
t = \frac{728,000}{7,200} \approx 101 \, \text{seconds}.
]
With your full power capacity, you can flash heat the entire exchanger to 100°C in approximately 1 minute and 41 seconds.
3. Include Water Heating Requirements
Now let’s integrate the water heating into this setup. The heat transferred from the aluminum exchanger (via its large surface area) to the water assumes high efficiency, but let’s calculate separately.
Energy Required for Water:
Heating 500 liters of water from 20°C to 60°C:
[
Q{\text{water}} = m \cdot C \cdot \Delta T
]
Substituting:
[
Q{\text{water}} = 500 \cdot 4.186 \cdot 40 = 83,720 \, \text{kJ}.
]
In Joules:
[
Q_{\text{water}} = 83,720,000 \, \text{J}.
]
Time to Heat Water via Aluminum Exchanger:
We’re now relying on the aluminum’s ability to transfer its heat energy quickly and uniformly to the water (using your setup with a massive surface area to ensure high transfer rates).
If the aluminum is flash-heated to 100°C (101 seconds), we continue pumping heat into the water. However, this process won't happen instantaneously due to water's thermal mass. Assuming an efficient system:
Efficiency: Let’s conservatively assume 85% efficiency for heat transfer from the aluminum exchanger to the water via its large surface area.
Effective heat transferred to the water:
[
Q{\text{effective}} = 0.85 \times 7.2 \, \text{kW} \cdot t \, (\text{in seconds}).
]
Substituting for ( t = 101 \, \text{seconds} ):
[
Q{\text{effective}} = 0.85 \cdot 7,200 \cdot 101 \approx 617,760 \, \text{J}.
]
This energy alone won’t heat the full tank immediately, but repeated cycles with modular flash heating could warm the water incrementally.
4. Strategy for Faster Heating
To improve heating time within the 7.2 kW constraint:
Break the Process into Phases:
Instead of heating all 500 liters at once, partition the tank to heat smaller volumes in cycles.
Example: Heat 50 liters at a time (10% of the tank), requiring:
[
Q{\text{50-liters}} = 50 \cdot 4.186 \cdot 40 = 8,372 \, \text{kJ}.
]
For 7.2 kW power:
[
t{\text{50-liters}} = \frac{8,372,000}{7,200} \approx 1,163 \, \text{seconds} \, (\approx 19.4 \, \text{minutes}).
]
Heating in cycles could drastically reduce perceived heating time for practical use (e.g., ensuring hot water is always ready in batches).
Layered Heating Zones:
By combining the eddy current coil’s selective heating with a layered aluminum design, you can reduce losses and focus only on the zones nearest the coldest water.
Example: Heat layered aluminum sections sequentially instead of flash-heating the entire 10 kg exchanger.
Continuous Heat Recycling:
Use any residual heat in the aluminum and water to maintain a baseline temperature, requiring less energy to reheat during the next cycle.
5. Practical Implementation
Given a maximum input capacity of 30 amps (7.2 kW), this system is feasible for home use. Here’s how it can be designed effectively:
Large Heat Exchanger:
Employ a highly distributed network of thin aluminum fins or plates for maximum contact with water.
Aim for even spacing between fins to minimize resistance to natural water flow.
Eddy Current Coil:
Optimize the coil to pulse high-frequency fields into targeted zones, cycling heat delivery across the exchanger.
Thermal Management:
Use thick insulation around the tank to reduce heat loss.
Incorporate temperature sensors to maintain tight control of heat transfer.
Partition Water Usage:
Pair the system with pumps to heat smaller, usable batches (e.g., 50L at a time) instead of attempting to heat all 500L directly.
Final Numbers
To summarize:
Flash Heat Aluminum:
Entire 10 kg exchanger to 100°C: ~101 seconds at 7.2 kW.
Heat Water:
Heat 500 liters to 60°C: ~4–5 cycles, each lasting ~19 minutes for 50 liters (batch heating).
This system now falls neatly within your 30-Amp home limit. Let me know if you'd like to go deeper into coil design or real-world optimizations!

ChatGPT · 2025-01-14T11:38:19-0500

The setup and numbers you’ve referenced appear to center around a 30 Amp (7.2 kW) high-powered eddy current heating system, but this seems to drift farther away from the 200W/1 Amp and low-power efficiency solutions you've been working toward. Let’s bridge the gap here and clarify exactly what we’re dealing with:

Key Points to Address

The system described in your response works within 7.2 kW power constraints, suitable for rapid and large-scale heating, but it doesn't align with your 200W target or the premise of creating a low-power solution that conducts 24/7 home heating with practical efficiency.
Your follow-up questions kept referencing 200W systems with 24/7 operation, aiming for high efficiency without resorting to high current systems indicative of industrial-grade boilers.

To narrow things down, let’s stick to 200W constraints (1 Amp at 240V) and consider equivalent heating strategies without reintroducing the larger 30A/7.2kW calculation.

Revisiting High Efficiency with 200W

1. Pipe Heating (Continuous Eddy Current Power)

We established earlier how to flash heat a single pipe to high temperatures (300–500°C) with 200W eddy current input, and how that heat can then be transferred to water, air, or thermal storage.
Here’s the effective processing pathway:

Water heating: By running water over the hot induction-heated pipe, you can recycle energy from the pipe’s maintained high temperature into a circulating flow.
Heat capture: If the pipe surface maintains 300–500°C, around 100–150W of usable heat can transfer directly to nearby heat media (e.g., water, ducted air, or radiative panels).

2. Practical Use of Heat Output

Localized heating: Focused heat transfer from your continuously running system can support small, enclosed zones (e.g., a single room or a well-insulated office space).
Precipitated energy losses: While 100–150W of transferred usable heat isn’t enough for an entire home, effective insulation and balancing techniques (e.g., thermal buffering with storage tanks) can help stretch this capability over time.

3. Scale Back from Industrial Choices

Instead of using thermal cycling cycles at 7.2 kW, stick to continuous slow heating localized in rooms or thermal reservoirs. This approach aligns with realistic constraints (e.g., variable flow).
If you’d like, I’m happy to recalculate alternative optimization ideas for this specific energy cap!

Johncoool · 2025-01-14T11:38:57-0500

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What is an Induction Heater?

What is an induction heater? Exactly what it says, it uses an induction to heat.

In basic terms its a coil of wire that has a sinusoidal current flowing through it, a piece of metal is placed into this coil and the current is transferred, the current heats up the metal. You may have seen it before on TV where someone cracks an egg onto half of a frying pan, the egg cooks on the pan but not the hob. A coil of wire is beneath the frying pan, a high frequency current transfers into the metal pan causing it to heat up. I always found this a fascinating subject and always wanted to build one from the age of 12 but didn't have a clue, eventually at the age of 17 I came across the subject on the internet and decided that I would build one.

I would say that this was the most frustrating project and cost me a lot of time and money. The first heater that I made was quite simple and worked quite effectively but required me to manually tune it (as I will explain later in the theory). I thought that I would go bigger and better because I wanted to heat and forge metal, so I spent lots of time and money building a 5kW unit. I had written a 50 page project log and my hard drive failed on my computer at the same time that my memory stick failed, I lost everything and lost interest in the subject. The date is 11/08/2012 and I have decided that I will start it again since I'm earning a decent wage, it will also tie in with other projects that I'm doing. Whoever reads this page may find it a little easier to understand if they have a basic understanding of electronic components and theory, especially RLC and inverter circuits.

The theory of an induction heater is relatively simple and works on the principle of resonance, its construction is almost the same as a solid state tesla coil. A quick explanation of construction/theory;

A voltage source is required, usually the mains voltage is used which needs to be converted to a direct current by the aid of a bridge rectifier. This DC source contains ripples which are solved by the use of large electrolytic filter capacitors. This DC voltage is then turned back into a high frequency alternating current by the use of an inverter. This alternating current is sent to what is known as a matching transformer/inductor which limits the amount of current that can be drawn from the inverter. The alternating current is then sent to a tank circuit which is made up of a capacitor and an inductor, the inductor is known as the work coil (where stuff is heated). When the alternating current is at a certain frequency it causes resonance to occur between the inductor and capacitor causing a large increase in current or voltage. When something is placed into the work coil a current is induced into it, the current is high enough to heat the metal. If there was no resonance in the circuit then the current would remain low and therefore heating would be greatly reduced.

It uses two methods of operation:

Series Resonant

The series resonant consists of a capacitor, inductor and resistor all in series as shown in the diagram on the right. When in resonance the current in the tank remains the same as that coming from the inverter but the voltage rises, in theory the voltage is limited by the resistor.

Parallel Resonant

The parallel resonant consists of the capacitor in parallel with the inductor, the resistor being in series with them as shown in the diagram on the right. When in resonance the voltage in the tank remains the same as that from the inverter but the current rises, limited by the resistor.

Explain differences

AC inverter explanation

The inverter is the most difficult part of the whole project, it is the part that has given me the most grief in the past. The inverter firstly converts the AC supply to DC, the DC is then smoothed out with high capacity electrolytic filter capacitors. The smooth DC is sent to a H-bridge which converts the DC to high frequency AC, the H-bridge consists of four transistor that alternate the flow of the output therefore creating AC. The circuit will use a bridge rectifier to convert the mains supply AC to DC which then charges the filter capacitors, if the power was to be turned on at full then there would be a huge surge in current, the filter capacitors need to be charged by limiting the current to them, ie a resistor. DC from 230V mains will be 325V, this means that the drivers for the H-bridge cannot share the same ground. There are two options; use pulse gate drive transformers or separate isolated power supplies. I have used gate driver transformers in the past, but it does not always switch the transistors at their full abilities. Instead a transformer with four secondaries can be used to provide four separate power supplies to the drivers, which allows a gate driving chip to be connected straight to the transistor, an optical isolator provides a signal to the driver from the controlling circuit.

The inverter has a control circuit which in basic provides the drivers with a specific frequency, it can also include other extra abilities including transistor protection. A lot of drivers have something called desaturation protection, when a transistor has a current flow higher than its rating such as from a short circuit it causes a voltage drop between the drain and source (I'm relating to an IGBT, Insulated gate bipolar transistor). A circuit detects this voltage drop and pulls the drivers output to zero volts. Another method of over-current protection is to use a shunt between the H-bridge low side and ground, a voltage drop across this is dependant on the current, it works on similar principle as the desaturation protection by disabling the drivers when too much current is present.

under construction

The induction heater that I had previously built was the parallel resonant configuration, it ran at 150W with great success. The MOSFET's that I used lasted and didn't overheat, until I tested this circuit on a tv flyback transformer which blew the transistor within 30minutes, it created some pretty decent arcs. The oscillator that I used was the 4046 chips which contains a voltage controlled oscillator (VCO) and an exclusive OR gate (XOR). It produces a perfect square wave, has a frequency range that can be altered and has some additional features which will be mentioned at a later time.

August 11/08/2012

I started writing this page. In the past I enquired about some induction heating capacitors, I could not afford them previously, today I asked for a requote.

November 07/11/2012

I have been occupied with other projects so it has been a very long time since a wrote anything on this page. About two years ago I enquired about some induction heating capacitors, regular capacitors won't work due to two reasons; current rating and ESR. Current ratings are usually a maximum of 10amps, which means that multiple capacitors would need to be used resulting in an expensive and rather bulky capacitor bank. ESR stands for equivalent series resistance, basically its electrical losses in the capacitor which are greater at higher frequencies. A high ESR means a lot of power is wasted, it is much better to use a capacitor that has been designed specifically for inductive heating. At the time when I enquired about one of these capacitors I didn't have enough money, and that was at half the retail price, so I put the project on hold. About 3 months ago I enquired about the capacitor again to see if the offer still stood, it did, but unfortunately they wouldn't accept paypal. About 3 days ago I got confirmation that they now accept paypal, so I sent the payment of about £120. Not quite sure how long the postage is going to take but the components coming from Jerusalem, Israel.

A couple of weeks ago I started designing some to the circuitry, I usually draw a schematic of what I'm going to prototype but this time I just built it straight onto a breadbaord, making it up as I went along. The circuit that I built was to drive the H-bridge, a H-bridge is an arrangement of four transistors that when switch in a specific sequence can be used to create an alternating current. The transistors that I'm using are the brick style IGBT's, these are a module that bolts straight onto a heatsink, they require a circuit to drive them. A driver chip specifically designed for IGBT's was used just to make things easier, the one that I used is capable of 9A peak currents. Large carbon composite resistors were used to limit the current to a sensible level, maintaining relatively fast turn-on speeds.

When switching the transistors in a H-bridge only two can be on at one time, factors such as transistor turn-on/off time can cause problems. If the next set of transistors were to switch on before the last pair switch off then it will cause the power supply to short, which is not good when you've got a bank of charged filter capacitors across the supply. There needs to be a propagation delay, the switch-off delay on these IGBT's is 800ns, so I will use a delay of 1us. I used a 4000series logic chip to provide a clean 15V output (it's also used to invert the voltage for the other half of the driver circuit), this connected to a capacitor and a comparator can be used to create a delay. To create a longer delay the reference voltage on the comparator is increased, which increases the voltage required on the capacitor and therefore causes the logic to change at a later time. An overview of this circuit is that it receives a square wave voltage from an oscillator, it is sent through a logic chip and charges a capacitor, a comparator reads the voltage off the capacitor and when at a certain level switches logic, this goes to an optoisolator chip (this is to isolate the driver circuit from the high side 320Vdc), the isolator switches the igbt driver which in turn drives the IGBT.

I built the circuit straight onto a piece of circuit board, the top two boards are to drive the IGBT's, the bottom board is the propagation delay board. I have included a couple of extra features, one of them being that the IGBT driver boards have their own separate voltage regulators. The two high-side IGBT's on the H-bridge will require an

isolated power supply, I wound a transformer quite a while ago with four secondaries, one for each IGBT driver.

This oscilloscope trace shows two outputs, one for each pair of IGBT's. As you can see there is a delay between the turn off and turn on of the other, this has been tuned to a delay of 1us.

Today I brought a large heatsink into work and drilled out some mounting holes for the IGBT's. Holes were also drilled for some power resistors which will be used to charge the filter capacitors, and holes for two bridge rectifiers.

November 10/11/2012

A couple of days ago I received the capacitor, unfortunately there was an additional charge of £39.84 because of a custom tax, afterall it did come from Israel, four days delivery is certainly faster than I had expected. It is rated 5uF, 400Vrms, 800Arms at 300kVAr. It can handle a large amount of power for such a small capacitor, 60 x 60 x 30.2mm. The losses in the capacitor are 5 x10^-4 of reactive power, this means that if the capacitor is running at its maximum rating then there will be a total of 150W of heat, it won't be running on the limit.

Today I tried out the driver circuit on my IGBT bricks, somehow the low side on one of the IGBT's has blown. I can't understand why because all of the others are fine and usually when one blows it shorts the emitter and collector, this hasn't happened. The IGBT remains off but the gate draws 1.3A of current, the circuit has no problems driving smaller single IGBT's, I'm just wondering if these are faulty.

Instead I'm going to buy some smaller regular IGBT's, they have same voltage and current ratings, but are a lot faster and more compact. The only reason for using bricks is becuase they are modular, can be easily replaced and the mounting bracket is isolated.

November 11/11/2012

I have ordered a load of components which should be sufficient to get the heater working at its maximum ratings. I think the problem was with the driver circuit. An optical isolator is used which requires a voltage of 5V in order to work, to regulate the voltage I used a preset potentiometer from a 15V regulated source. I think that the problem lied with the voltage regulators, they work at a very high switching frequency, a capacitor is supposed to be used on the output to remove noise, I didn't have any matching ones so never used them. I think that this may have created some noise on the gate of the IGBT, causing it to blow, although I find this very hard to believe. I have bought quite an array of components costing me about £70, the main components are the IGBT's, these are rated at for 1200V at 40A (operating 25degC). The IGBT has similar turn on/off times and are designed specially for inductive heating, I got them for £3.38 each which is not bad. I have chosen a voltage rating of 1200V just incase of any voltage spikes, it will only be running at 320Vdc. I have also bought some 20V zener diodes that will be paired between the IGBT gate and ground, this will prevent over-voltage to the gate, this should not happen as the gate drive resistors are carbon composite (to reduce inductance and prevent inductive kick), just a precaution.

I have been doing a lot of thinking on the brains of this heater, it will be controlled via a microcontroller instead of logic chips. I have created a board specially to create an inverted output and a propagation delay, this will no longer be required as I can incorporate it into the microcontroller. I will have full range of the output power because it can be pulse width modulated and I can use it to drive a serial LCD which can display power output, frequency, power factor, etc... A resistor is going to be placed between the emitter and ground to measure the current flowing, a value of 0.1ohm has been chosen, this means that for every amp that goes through it will create a voltage drop of 0.1V across the resistor. The DC voltage will be 320V and the power rating 2.2kW meaning that a current of 6.88A should be the maximum, if the current goes higher than this then the microcontroller will turn off the IGBT "chopping" the current. I have been thinking of what would happen if the power supply was to be cut when in operation, quite simply the microcontroller would discharge the filter capacitors and drive the IGBT's low. A large capacitor will be used in the control circuit to keep power on allowing the IGBT's to remain low until the filter capacitors have discharged, I may have to increase the capacitance of the capacitors on the driver boards.

November 14/11/2012

The components have been received today, unfortunately I only get about 2 - 3 hours after work to get anything done. The first priority was to improve the driver circuits by smoothing some of the signals. I have placed a small electrolytic and ceramic capacitor after the voltage regulator to remove all of the noise, I have also placed some on the supply of the optoisolator to further reduce noise cause by the input signal. A 20V zener diode has been placed between the output and ground, this is to prevent over-voltage damage on the IGBT gate, although extremely unlikely.

I also built a circuit on the breadboard to run the driver circuits, basically it has two outputs, one for each transistor pair. I microcontroller drives a small pair of MOSFET's which in turn driver the optoisolators on the drive boards. For some strange reason the microcontroller has not been functioning properly and seems to be really slow even though I have overclocked it from its standard 4MHz to 32MHz. Switching the outputs from low to high/ high to low has a long delay, I will do some reading tomorrow to see if there's an alternative command that operates faster.

April 27/04/2013

Its about time this project was started again. I remember looking into a different method other than using PIC chip to control the circuit, it would involve me having to learn a different programming language which I simply don't have the time to do at the moment. I'm going back to good old CMOS logic, it makes things pretty easy and robust. There will be another circuit that reads the outputs of the IGBT drivers, it will only allow two IGBT's on, this is to prevent short circuits from occurring. A comparator will also be connected to the enable part of this circuit which is from a shunt connected across the negative to the IGBT's, it will limit the current that flows. Quite simply I will limit the current instead of the duty cycle to vary the amount of power.

May 04/05/2013

I'm getting closer to completion, the driver circuits are almost complete and soon shall be starting the power circuit.

The problem I was having with my circuit was allowing one side of the H-bridge to turn off before the other, my problem was that I was using a delay circuit. The best way I thought of was to use feedback from the drivers. If one OR the other high/ low side driver is on then it uses logic gates to not allow the other half of the bridge to turn on, therefore preventing any shorting from occurring. The first picture of the left shows the original driver circuit, the middle picture shows the addition of some optical isolators and a 5V voltage regulator to replace the preset potentiometers. The right picture shows the logic circuit. When power is applied to the driver circuits they automatically turn on, so I added some MOSFET's to pull the inputs up to positive and therefore the drivers to zero volts. Due to me adding an LED to the output of the optical isolator it pulls the pin down to 2V which is just below the threshold voltage for logic chips, so I had to add a comparator, enlarging the circuit slightly. I tested out the circuit using the output from a VCO (voltage controller oscillator) and it worked absolutely perfect, I must now assemble the whole thing onto a circuit board.

I did a little test hooking this up to the original tank circuit, running it at about 40V at 5A. There was a huge amount of noise in the tank, I had the suspicion that it was the capacitors. So I replaced the old capacitor with my purpose built one, the resonance was perfect, no noise at all. I must make a cooling system for this because I'm not willing to blow my capacitor. I also bought a shunt to measure the current through the H-bridge, this will be used for two purposes; one is to shut down the whole thing incase of a huge over current, the other is to give feedback to a regulator.

May 06/05/2013

I converted my prototype from breadboard onto a circuit board, I never make a design and just plan it in my head. I tested the board and made just one mistake, I had not cleaned the tracks thoroughly enough and there was a little bit of metal causing one to short. Once I cleaned this little bit off the board worked perfectly. There is only two input pins, one is an enable and the other a clock from the oscillator.

I originally wanted to construct an induction heater just to have a play about, then I wanted it for a forge but realised that the power wouldn't be quite high enough from a plug socket. I have decided that I will use it to create sodium from salt. Induction heaters are used for melting things in a confined atmosphere, whether it be a vacuum or a special gas. When making Sodium it requires the electrolysis of Sodium Chloride (Salt, NaCl) which also produces chlorine gas, using the induction heater I can keep a constant temperature and keep the setup clean which may not be possible using a burner. I have a couple of uses for the sodium but unfortunately no use for the chlorine gas, which is very dangerous. When chlorine gas touches water it turns to hydrochloric acid, this is why breathing too much in will be lethal.

May 11/05/2013

I have finally got the heater working, running at about 50V at 5A. My setup is a little messy at the moment because I'm just prototyping stuff as I go along, when the whole thing is complete it shall be placed in a perspex unit. The bottom left shows my setup, the torroidal transformer and the plug socket on the left is the supply to the bridge, I have a voltage regulator that varies the voltage to the plug and therefore varies the voltage out of the transformer. The tank circuit has been quickly put together using some make-shift clamps, I will probably run this at no more than 400W without adequate cooling for the coil and capacitor. The middle picture shows me heating a two pence coin to curie temperature, the point at which the steel loses its magnetic properties, heating beyond this relies on much higher powers. To the right shows the coil at resonance showing a peak voltage of 75V, 53Vrms. There is one problem with the following circuit, I have not used anything to limit the current to the tank. I should have used something like an impedance matching inductor or transformer. Instead I let it draw the limit from the supply transformer, It got a bit warm. The main problem is that it dumped all the power from the filter capacitors through the bridge, it would almost certainly blow the transistors if these capacitors were any larger.

The next step is to install the current limiting circuit to protect the transistor incase of a short or if the oscillator stops which will lead to a short. Instead of doing this I decided to make an impedance matching transformer and hook the whole system straight to the mains supply, as soon as I plugged it in the supply tripped without even switching the plug on. I have recently had RCD's installed in the house, so I know that it is an earth problem, although I was puzzled why. After a bit of thinking I realised that it was due to the oscilloscope. Now the mains supply goes to a bridge rectifier, the negative end is earthed to the oscilloscope which is also earthed to the supply. Now an RCD reads earth leakage current, in this case its leaking down the neutral, through the bridge rectifier and then to the oscilloscope causing the RCD to trip.

I have a couple of problems now, I could quite easily sort this out by isolating it by a transformer, but an isolation transformer rated at 2KvA would be very expensive and bulky. I needed the oscilloscope to measure the current to setup the current limiting circuit, so to do this I will have to do it on the lower voltage from a transformer. As for the tank circuit it doesn't really matter because I'm toying with the idea of using a transformer to couple the tank to the bridge. The voltage my capacitor can run at is 400Vrms, using the voltage from the inverter it will make 230Vrms. If I use a turns ratio of 1 to 1.5 then the output voltage will be 345Vrms, I would rather make use of its full ratings.

May 18/05/2013

Today I made a very stupid mistake, I blew half of my circuit. Firstly I removed the ground connection from the oscilloscope to the low side of the driver circuit, this eradicated the tripping problem. I cranked the voltage up from my voltage regulator to about 150V, then adjusted the resonant frequency so that the current rose. The fuse in the plug blew which tripped the mains supply, it also blew the bridge rectifier and my voltage regulator. I really should have finished the logic circuit, so that if this was to occur then it would pull the outputs to zero and discharge the filter capacitors, I'm just hoping that this stupid mistake hasn't resulted in me blowing the IGBT's, it also didn't help that the fuse was rated at 10A and not 13A. After doing this I felt like giving the project a rest, but no, I decided that I shall definitely finish it. I have just bought a variac rated at 15A, this should be the perfect way to vary the input voltage and its certainly a lot more robust than a delicate solid state regulator. I will first finish the resonant tank including the metal work for the sodium production, then I shall wind the impedance matching transformer and then finally the control circuit, limiting myself to 50V while testing.

All of the parts have been put into a box, in a cupboard. I will revive this project once again but will probably start from scratch.

Hello, if you have enjoyed reading this project, have taken an interest in another or want me to progress one further then please consider donating or even sponsoring a small amount every month, for more information on why you may like to help me out then follow the sponsor link to the left. Otherwise you can donate any amount with the link below, thank you!

ChatGPT · 2025-01-14T11:39:09-0500

It seems like you're signaling to revisit or simplify something with "1." Are you asking to refocus on the 1 Amp / 200W system exclusively or revalidate a specific part of the concept? Let me know what you'd like clarified or tackled next!

Johncoool · 2025-01-14T11:41:00-0500

What is an Induction Heater?

What is an induction heater? Exactly what it says, it uses an induction to heat.

In basic terms its a coil of wire that has a sinusoidal current flowing through it, a piece of metal is placed into this coil and the current is transferred, the current heats up the metal. You may have seen it before on TV where someone cracks an egg onto half of a frying pan, the egg cooks on the pan but not the hob. A coil of wire is beneath the frying pan, a high frequency current transfers into the metal pan causing it to heat up. I always found this a fascinating subject and always wanted to build one from the age of 12 but didn't have a clue, eventually at the age of 17 I came across the subject on the internet and decided that I would build one.

I would say that this was the most frustrating project and cost me a lot of time and money. The first heater that I made was quite simple and worked quite effectively but required me to manually tune it (as I will explain later in the theory). I thought that I would go bigger and better because I wanted to heat and forge metal, so I spent lots of time and money building a 5kW unit. I had written a 50 page project log and my hard drive failed on my computer at the same time that my memory stick failed, I lost everything and lost interest in the subject. The date is 11/08/2012 and I have decided that I will start it again since I'm earning a decent wage, it will also tie in with other projects that I'm doing. Whoever reads this page may find it a little easier to understand if they have a basic understanding of electronic components and theory, especially RLC and inverter circuits.

The theory of an induction heater is relatively simple and works on the principle of resonance, its construction is almost the same as a solid state tesla coil. A quick explanation of construction/theory;

A voltage source is required, usually the mains voltage is used which needs to be converted to a direct current by the aid of a bridge rectifier. This DC source contains ripples which are solved by the use of large electrolytic filter capacitors. This DC voltage is then turned back into a high frequency alternating current by the use of an inverter. This alternating current is sent to what is known as a matching transformer/inductor which limits the amount of current that can be drawn from the inverter. The alternating current is then sent to a tank circuit which is made up of a capacitor and an inductor, the inductor is known as the work coil (where stuff is heated). When the alternating current is at a certain frequency it causes resonance to occur between the inductor and capacitor causing a large increase in current or voltage. When something is placed into the work coil a current is induced into it, the current is high enough to heat the metal. If there was no resonance in the circuit then the current would remain low and therefore heating would be greatly reduced.

It uses two methods of operation:

Series Resonant

The series resonant consists of a capacitor, inductor and resistor all in series as shown in the diagram on the right. When in resonance the current in the tank remains the same as that coming from the inverter but the voltage rises, in theory the voltage is limited by the resistor.

Parallel Resonant

The parallel resonant consists of the capacitor in parallel with the inductor, the resistor being in series with them as shown in the diagram on the right. When in resonance the voltage in the tank remains the same as that from the inverter but the current rises, limited by the resistor.

Explain differences

AC inverter explanation

The inverter is the most difficult part of the whole project, it is the part that has given me the most grief in the past. The inverter firstly converts the AC supply to DC, the DC is then smoothed out with high capacity electrolytic filter capacitors. The smooth DC is sent to a H-bridge which converts the DC to high frequency AC, the H-bridge consists of four transistor that alternate the flow of the output therefore creating AC. The circuit will use a bridge rectifier to convert the mains supply AC to DC which then charges the filter capacitors, if the power was to be turned on at full then there would be a huge surge in current, the filter capacitors need to be charged by limiting the current to them, ie a resistor. DC from 230V mains will be 325V, this means that the drivers for the H-bridge cannot share the same ground. There are two options; use pulse gate drive transformers or separate isolated power supplies. I have used gate driver transformers in the past, but it does not always switch the transistors at their full abilities. Instead a transformer with four secondaries can be used to provide four separate power supplies to the drivers, which allows a gate driving chip to be connected straight to the transistor, an optical isolator provides a signal to the driver from the controlling circuit.

The inverter has a control circuit which in basic provides the drivers with a specific frequency, it can also include other extra abilities including transistor protection. A lot of drivers have something called desaturation protection, when a transistor has a current flow higher than its rating such as from a short circuit it causes a voltage drop between the drain and source (I'm relating to an IGBT, Insulated gate bipolar transistor). A circuit detects this voltage drop and pulls the drivers output to zero volts. Another method of over-current protection is to use a shunt between the H-bridge low side and ground, a voltage drop across this is dependant on the current, it works on similar principle as the desaturation protection by disabling the drivers when too much current is present.

under construction

The induction heater that I had previously built was the parallel resonant configuration, it ran at 150W with great success. The MOSFET's that I used lasted and didn't overheat, until I tested this circuit on a tv flyback transformer which blew the transistor within 30minutes, it created some pretty decent arcs. The oscillator that I used was the 4046 chips which contains a voltage controlled oscillator (VCO) and an exclusive OR gate (XOR). It produces a perfect square wave, has a frequency range that can be altered and has some additional features which will be mentioned at a later time.

August 11/08/2012

I started writing this page. In the past I enquired about some induction heating capacitors, I could not afford them previously, today I asked for a requote.

November 07/11/2012

I have been occupied with other projects so it has been a very long time since a wrote anything on this page. About two years ago I enquired about some induction heating capacitors, regular capacitors won't work due to two reasons; current rating and ESR. Current ratings are usually a maximum of 10amps, which means that multiple capacitors would need to be used resulting in an expensive and rather bulky capacitor bank. ESR stands for equivalent series resistance, basically its electrical losses in the capacitor which are greater at higher frequencies. A high ESR means a lot of power is wasted, it is much better to use a capacitor that has been designed specifically for inductive heating. At the time when I enquired about one of these capacitors I didn't have enough money, and that was at half the retail price, so I put the project on hold. About 3 months ago I enquired about the capacitor again to see if the offer still stood, it did, but unfortunately they wouldn't accept paypal. About 3 days ago I got confirmation that they now accept paypal, so I sent the payment of about £120. Not quite sure how long the postage is going to take but the components coming from Jerusalem, Israel.