150-250w induction heater / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

150-250w induction heater

1 2 next

Move Thread

LAN_403

blackwoolf511

Tue Dec 20 2011, 10:07PM

Registered Member #4278 Joined: Tue Dec 20 2011, 09:03PM
Location:
Posts: 17

Hello everybody!

I'm new on this forum (and electronics too).
I need some help to build an induction heater for my tea thermos.
I already thought of using an "induction cooker circuit " but they are overpowered (1200w are useless for my needs)
my requirements would be:
10-20v dc
15a max
freq ?
heat output 60-250C (possibly with a regulator).

I apreciate any kind of help or a schematic...
Many thanks.

Marko

Wed Dec 21 2011, 05:13AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

blackwoolf511

Wed Dec 21 2011, 09:30AM

Registered Member #4278 Joined: Tue Dec 20 2011, 09:03PM
Location:
Posts: 17

Hello Dr. Pork!
Many thanks for your help.
I forgot to mention the coil turns;
how would this schematic be if i put a 17 turn coil(istead of the 5 turns on the pictures) so i could warm the whole water on the thermos to could save some time?

Marko

Wed Dec 21 2011, 10:18AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

blackwoolf511 wrote ...

Hello Dr. Pork!
Many thanks for your help.
I forgot to mention the coil turns;
how would this schematic be if i put a 17 turn coil(istead of the 5 turns on the pictures) so i could warm the whole water on the thermos to could save some time?

I don't know... it primarily depends on coupling between the wire and thermos, as well as wall material and thickness. You could try and then decrease the inductance if necessary.

Marko

IamSmooth

Wed Dec 21 2011, 06:16PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

blackwoolf511 wrote ...

I forgot to mention the coil turns;
how would this schematic be if i put a 17 turn coil(istead of the 5 turns on the pictures) so i could warm the whole water on the thermos to could save some time?

If you put more turns this is what happens:
1. you will heat a larger area
2. the induced voltage will be less, so there will be less heating for a fixed region for the same input voltage to the inverter
3. the current draw will be less from your mains for the same input voltage
4. the resonant frequency will decrease since you increase the inductance of the coil

Thus, if you use less turns and maintain the input current, you can significantly increase your power input into the heated piece.

Example: You have a one turn primary, and the workpiece is considered one turn. For simplicity, assume the load resistance is 1R. The input voltage is 10V. The secondary will also be 10v and the amps will be 10A for 100W. This means the input is also 100W @ 10A. If we double the coil's turns to two, the secondary voltage is now 5V @ 5A. This means for the same 10V input you only draw 2.5A. You have spread out the heating region, but you are only putting in 1/4 the wattage.

If you have a lot of voltage at your disposal, you can use a lot of turns to keep the input current down. If you don't have a lot of input voltage, you might want to use less turns, but keep in mind that you will draw more primary current.

I have a lot of theory, diagrams, descriptins and examples that I have put together at this site.

As a side note, I found a retort cement by Hercules that will go up to almost 3000F. This should allow many of you to fashion crude crucibles for melting metals like copper or iron without melting the container.

SWA_Flyer

Thu Jan 12 2012, 11:57PM

Registered Member #4263 Joined: Wed Dec 14 2011, 05:21PM
Location:
Posts: 4

Iamsmooth, i looked at the tutorial for your induction heater, very well written and prepared, much appreciated. However, I could not find how many turns are on T1. I know that it is a 1:1:1 on a toroid. Are the windings for T1 dependent upon frequency used?

IamSmooth

Fri Jan 13 2012, 05:40AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

The coupling transformer is discussed here.

If you are referring to the gate drive transformer for driving the switches,
I have the part number in the schematics. I got it from mouser.

SWA_Flyer

Sun Jan 15 2012, 03:47AM

Registered Member #4263 Joined: Wed Dec 14 2011, 05:21PM
Location:
Posts: 4

Got it. One more question What is the negative 15 Vdc regulator used for? Did not see in the schematic where is was used. Thank you again

IamSmooth

Mon Jan 16 2012, 03:35AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

The schematic is here with the part LM6172. It is a HIGH SPEED amp. High speed is needed for the frequency used. It has been a while, but if I recall, the standard op-amps could not put out enough voltage at these high frequencies, so I tracked this puppy down. It is used to to convert the capacitor tank sinusoidal voltage into a square-wave, which is used as one of the PLL inputs.

Many miss the more detailed, complicated schematics for the 10kw unit. This unit includes the microprocessor-controlled resonant-lock technology that I developed for my project. I got a lot of help from "Neon John" and this forum for the induction unit, but I worked out the software code for the microprocessor to track the inverter voltage and capacitor voltage in order to determine the resonance point. The LM6172 requires +15v and -15v, which is the reason for the negative supply.

This section also goes into detail about constructing a coil for levitating and melting metals. This is one of several videos that I have demonstating this effect.

Here is the datasheet.

I also want to mention that if you want to know the temperature of the metal you can buy an IR thermometer or use an iPhone app Thermal Light which uses the irradiating color of the object (Black Body radiation) to determine the temperature. I wrote it so I could measure the temperature of steel and copper to know when it was near the melting point.

SWA_Flyer

Mon Jan 16 2012, 07:33AM

Registered Member #4263 Joined: Wed Dec 14 2011, 05:21PM
Location:
Posts: 4

IamSmooth, you have been a great help! Thank you once again. Will post pics when I get mine complete

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob