Chinese 150 Watt Induction Heater, unboxing and test.

Review and test of a mini induction heater. At just 12V 10-15A you can have a small and effective induction heater for your work bench.

Chinese 1800 Watt Induction Heater – Horizontal Oven Heat Insulation Test

Test with using regular mineral wool for house insulation, to insulated the work coil in order to achieve higher steel temperatures. Here is another try, …

Chinese 1800 Watt Induction Heater – Heat Insulation Test

Test with using regular mineral wool for house insulation, to insulated the work coil in order to achieve higher steel temperatures.

Chinese 1800 Watt Induction heater, 10 minute stress test at 1500W

This test is being run at 36VDC and everything stays cool over a course of 10 minutes, I would say it can run stable at …

2200 Watt server power supply for induction heating

A new 2200 Watt power supply made from server power supplies, and with steady cameras 🙂 Test of it in a long induction heater run …

Chinese 1800 Watt Induction heater, 5 minute stress test

5 minute stress test at full power. 1800 Watt peak input power.

Unboxing a Chinese 1800 Watt Induction heater

I finally got around to get the IH out of the box and repair it, here is part 1 of a series of videos on …

Royer induction heater

Published 18. January 2013. Updated 21. March 2019.

Introduction

The Mazilli ZVS flyback driver is well-known throughout the high voltage community for its simplicity and ability to deliver 20-50 kV at high currents for a flyback transformer.

About one and a half year ago, Marko from 4hv.org gave the circuit a comeback with it converted to a simple induction heater.

I build the circuit as a proof of concept model in order to show it to my father that would like to start doing black smith work on small knifes.

To explore all my induction heaters, including the Chinese 1800 Watt induction heater, check out my youtube playlist for all induction heater related projects: https://www.youtube.com/watch?v=N1tg3mQL7lQ&list=PLw4xMO1xCMSUOj19zUmFE2-a2lcFBuzX_

 

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

 

Considerations

The MOSFETs used need a voltage rating about 4 times higher than the supply voltage and a on-resistance below 150 mΩ. In ZVS operation the switches see a voltage that is π times input voltage, so 4 times rating of input voltage leaves some head room for playing it safe.

If supply voltage gets over 40 VDC, consider using resistors between 470R-800R for the gates. Supply voltage needs to be minimum 12 VDC, lower than 470R gate resistors can be used in that case, if supply voltage dips under 10 VDC, there is a risk of MOSFETs failing from overheating by working only in the linear region or short circuit if one of them stops switching.

Supply voltage should not exceed 60 VDC, as this is very close to 200 VDC across the MOSFET. The internal construction of MOSFETs with a higher voltage rating makes them unsuitable for use in a self oscillating circuit like this Royer oscillator.

A MMC is made from 27 capacitors to avoid excessive heating in a single capacitor. The capacitors will still heat as massive current flows between the tank and work coil. To get a good result, a large tank capacitance is needed, if a capacitance lower than 4 uF is used, results might be disappointing. It is strongly advised to use a capacitor with made from polypropylene (MKP) or similar that can handle large RMS currents, it might even be necessary to water cool the capacitor too. A MMC as the one I use here can only withstand short run times and will even then heat up.

The value of the inductors are advised to be between 45 to 200 uH and depending on core material the number of turns varies a lot, use a LCR meter to check the values.

Water cooling of the work coil is a must! Even at just small runs with moderate power input as the ones I have conducted, the work coil would take damage from heat.

 

Specifications

Voltage supply 35 VDC smoothed with 40000 uF
MMC 3 uF from 9 in parallel strings of 3x 2 275 VAC MKP X2 capacitors in series.
Power consumption 650 Watt.
Best result Between red hot and white hot M10x20mm bolt

 

Schematic

 

Construction

17th January 2013

I succeeded in putting the entire setup together from parts I have salvaged from old equipment, only the MOSFETs was bought new and used before.

The transformer takes 230 VAC in for 32 VAC out, properly around 700 VA transformer estimated from the core size. It is rectified with a 25 A bridge rectifier smoothed with 40000 uF capacitance from four electrolytic capacitors 70 VDC / 10000 uF each.

The inductors are made from ferrite transformer cores from old power supplies. 14 turns of 1,5 mm^2 gave approximately 130 uH inductance.

Two IRFP250N MOSFETs mounted on each their fairly small heat sink, but big enough for the circuit to run for a couple of minutes and only get a little above hand warm. The heat sinks are glued together with a piece of acrylic plastic in-between to insure electrical isolation between the two heat sinks.

The work coil is made from 5 turns of 8 mm copper tubing, giving approximately 0,477 uH. The MMC consists of 9 parallel strings of 3 in series Rifa 1 uF / 275 VAC MKP X2 capacitors for 3 uF. This gives a resonant frequency calculated to about 133 kHz.

Measurements during a run of heating a M10x20 mm bolt at 33 VDC in, 260 VAC at 2.5 A input into transformer.

Resonant frequency is measured to 106 kHz. The measured frequency is different from the calculated as the work piece will influence on the coils electromagnetic properties.

In the following oscilloscope screenshot:

Yellow: Inverter current, here measured to 10 Ampere.

Blue: Inverter voltage, here measured to 100 Volt.

In the following oscilloscope screenshot:

Yellow: Tank current, here measured to 200 Ampere.

Blue: Tank voltage, here measured to 100 Volt.

Three pieces of metal heated to what is possible with input voltage of 35 VDC.

 

Conclusion

A good and reliable oscillator as long as supply voltage is kept within safe area of operation for the MOSFETs and only short run times are used unless there is used good components and water cooling on work coil, MOSFETs and capacitors.

Further improvements in use as a heater / melter would be a higher supply voltage.

 

Demonstration

Royer induction heater – first test

This is the first test run of a royer induction heater running at 650 Watt, there is heavy voltage sag on the DC supply. The …

Mazilli ZVS flyback driver

Introduction

The Mazilli ZVS flyback driver is well-known throughout the high voltage community for its simplicity and ability to deliver 20-50 kV at high currents for a flyback transformer.

I build this circuit almost a year ago on a vero board, but it kept blowing the thin traces due to high currents flowing. I eventually put the project in a box and forgot all about it.

Inspired by the point to point soldered designs Myke from the 4hv.org forums often uses, I tried to make something in that manner, not as pretty as his work though.

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

Considerations

The MOSFETs used need a voltage rating about 4 times higher than the supply voltage and a on-resistance below 150 mΩ

5 + 5 primary windings are suitable for voltages between 10 to 40 VDC, at higher voltages additional windings will be needed. Experiment with the number of windings to improve performance. Too few windings will result in excessive heating and too many will result in reduced power output.

A MMC is made from 6 capacitors to avoid excessive heating in a single capacitor.

This driver will push as much power as it can, so be sure to use flyback transformers that can handle the abuse if you want it to live.

 

Specifications

Voltage supply 35 VDC from a rewound microwave oven transformer.
MMC 0.66 uF from series string of 3x 2 275VAC MKP X2 capacitors in parallel .
Power consumption 400 Watt.
Longest arc 100 – 110 mm long white arcs

Schematic

Construction

15th may 2009

I have now rebuild the driver using 2.5mm² / 14AWG wire for a good current ability, larger heat sinks and a MMC to avoid as much heating as possible.

Sparks

16th may 2009

I found 4 different flyback transformers from my collection, among these are a 1980’s Bang & Ollufsen television flyback. A small flyback from a photocopier. A  flyback from a 1990’s portable television, it is without screen and focus resistor networks. A flyback with rectifier tube from a black & white 1950’s television.

The pictures with long arcs about the size of  100 – 110 mm was made with the 1980’s Bang & Ollufsen flyback transformer.

Conclusion

It was well worth it to rebuild this driver. It can now handle long run times with little heating despite pushing out around 400 Watt  of power!

Demonstration