Building a Safe and Efficient Induction Heater Circuit: Tips and Tricks

In summary, this personal project is UL safety compliant if you are running it off of a 12v car battery.
  • #1
gary350
253
52
TL;DR Summary
FUN induction heater circuit.
If you have not built an induction heater yet it is a fun project. Build the small circuit with 6 yellow capacitors first.

Induction heater is a fun project. I built a small induction heater then I wanted a more powerful one. A small unit is so simple you can build it in about 2 hours work. A larger more powerful unit will take longer. If you take your induction camping it works great to run it on your 12v car battery.

I built my largest induction heater from a microwave oven transformer. Remove the 2000v secondary coil, replace it with enough #12 solid copper wire to get 12v to 15vdc. I have about 15 MOTs they all have 100 turns on the primary coil. Math is easy for the secondary coil running on 120vac on the primary = about .833 vac per turn on the secondary.

I have not experimented with a flat induction coil the value must be 2. uh minimum value. Buy a, resistor, capacitor, inductor, meter about $35. on ebay to test your coils. The choke coil needs to be large enough not to saturate or it will stop working at a certain power range then current suddenly goes to maximum then mosfets explode. Very low internal mosfet resistance works best it prevents mosfets from over heating easy.

Here is my induction circuit, leave off the transformers so you can run it on a car battery if that is what you want. My small induction heater will heat a 1/4" steel rod red hot in about 3 minutes. My 1400w induction heater heats a 1/4" steel rod red hot in 7 seconds. You don't need 1400w to heat food it will burn before food has time to cook.

My induction heaters all have the same circuit drawing for the exception of larger power supplies and larger L2 choke coil for higher power units. If you change #10 circuit copper wire to a smaller wire skin effect goes up and the circuit efficiency goes down. My induction heat is several times smaller than the 1400w power supply as you can see in the photos.

Be sure to connect the caps in a box shape like a Rail Gun cap bank charge and discharge is much faster. Build the small unit with the 6 yellow color caps first. I use insulated Romex solid copper house wire. Be sure to use insulated wire if you accidently touch the osc coil with metal osc stops then 1 of the mosfets will explode.

You can build the small circuit for $15. The larger circuit only cost be extra for a 100a bridge rectifier and the meter. I salvage parts from old TV and old computer power supplies. 10 mosfets are $6 free shipping on ebay if you order from a seller in China.
100_6362.JPG
100_6779.JPG
100_6780.JPG
100_6781.JPG
100_6778.JPG
 
Last edited:
  • Informative
Likes Tom.G
Engineering news on Phys.org
  • #2
I'm not able to open your attachments. It's good that you are running this off of a safe low voltage like 12V. You do have a fuse in series between the battery and your device, right?
 
  • #3
I accidently posted this 2 times not sure what happened?????
 
  • #4
gary350 said:
I accidently posted this 2 times not sure what happened?????
Ah, I can see the schematic now. How come it shows AC Mains input at the left if you are running it off of a battery?
 
  • #5
berkeman said:
Ah, I can see the schematic now. How come it shows AC Mains input at the left if you are running it off of a battery?
The circuit with the yellow color caps is for a 12v car battery or a 12v to 15v DC power supply. The larger induction heater circuit uses a transformer to run on 120vac house wall current. Both units will run on a car battery but on the work bench I use 120vac to a transformer to get 15vdc up to 30vdc.
 
  • #6
gary350 said:
The larger induction heater circuit uses a transformer to run on 120vac house wall current.
Which UL safety standard did you design that version to comply with?
 
  • #7
berkeman said:
Which UL safety standard did you design that version to comply with?
The final version of the unit needs to be inside a protective case so you can't stick you finger in it and get shocked on 15vdc.
 
  • #8
gary350 said:
The final version of the unit needs to be inside a protective case so you can't stick you finger in it and get shocked on 15vdc.
That's not what I asked. 15V is not a shock hazard.

Thread is closed temporarily for Moderation. Please send me a PM with your full schematic showing the AC Mains connections and tell me what construction details are important to make this personal project UL safety compliant. Thanks.
 

Similar threads

Replies
4
Views
1K
  • Electrical Engineering
Replies
3
Views
1K
Replies
5
Views
825
  • Electrical Engineering
Replies
5
Views
3K
  • Electrical Engineering
Replies
5
Views
1K
  • Electrical Engineering
Replies
2
Views
1K
  • Electrical Engineering
Replies
1
Views
869
  • Electrical Engineering
Replies
5
Views
1K
  • Electrical Engineering
Replies
1
Views
970
  • Electrical Engineering
Replies
2
Views
1K
Back
Top