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Royer induction heater

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LAN_403

Redstone

Sat Sept 08 2012, 07:41PM

Registered Member #2578 Joined: Sun Dec 27 2009, 09:21PM
Location: USA Utah
Posts: 31

Marko I noticed that the inductors you are using are yellow and that you said that you got them out of a PC power supply, from what I have experienced they are used with DC to filter ripple out and are powdered iron and not ferrite. I believe that is why they get hot when you use them at high power.

m4ge123

Sun Sept 09 2012, 12:42AM

Registered Member #4118 Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140

D Rosey wrote ...

Marko I noticed that the inductors you are using are yellow and that you said that you got them out of a PC power supply, from what I have experienced they are used with DC to filter ripple out and are powdered iron and not ferrite. I believe that is why they get hot when you use them at high power. after they are replaced you should be able to note better performance.

See

mohiuddinHimel

Sat Sept 29 2012, 08:26AM

Registered Member #4254 Joined: Sat Dec 10 2011, 09:36PM
Location: Dhaka, Bangladesh
Posts: 27

hi marko,

after testing the miniature version of your circuit i wish to build a bigger one. i'll parallel four irfp250. but um stuck with the power supply.....specially with the transformer. i'll order for a big transformer but confused with the rating.

will a 220/35, 20amp transformer be able to give me at least 700 watts??? any suggestion??

Sigurthr

Sat Sept 29 2012, 03:32PM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

Multiply secondary voltage by secondary current rating to get the VA (or wattage) rating of the transformer.

So a 220V primary, 35V secondary rated for 20A would be 700VA. It is normal for transformers to drop in secondary voltage under heavy load though so depending on the actual impedance of the transformer you may get less than 700VA out due to voltage sag.

For example I have a 120:12 2A transformer which under 2A load drops to only 9V. The transformer is only capable of 18VA despite appearing to be a 24VA transformer.

mohiuddinHimel

Sat Sept 29 2012, 06:30PM

Registered Member #4254 Joined: Sat Dec 10 2011, 09:36PM
Location: Dhaka, Bangladesh
Posts: 27

"It is normal for transformers to drop in secondary voltage under heavy load though so depending on the actual impedance of the transformer you may get less than 700VA out due to voltage sag"

So should i increase the current capability to achieve 700 VA or more under loaded condition???

Marko's heater draws huge power when loaded. The voltage sags as well(last time it went to 17volts from 32 volts ). To achieve more than 700 watts what should be the ideal transformer rating??

Gabriel35

Mon Oct 01 2012, 08:27PM

Registered Member #2310 Joined: Wed Aug 19 2009, 08:04PM
Location: Santa Catarina - Brazil
Posts: 169

I Think a 43VAC (rectified becomes ~65v) Will be good for that application.

mohiuddinHimel

Tue Oct 02 2012, 07:03PM

Registered Member #4254 Joined: Sat Dec 10 2011, 09:36PM
Location: Dhaka, Bangladesh
Posts: 27

Thanks gabriel....i've already done with the transformer....its 35Vac...rectified and it will give me roughly 50VDC. Capable of 30 Amps. I've also got a variac which i plan to adjust the voltage if it sags too much.

Um now really confused with the capacitance. Marko said for lower power you need larger capacitance (like 4uf) and for higher power you should use high voltage and less capacitance. So, to get maximum power output at the work piece what capacitance should i choose?

In my country MKP/FKP capacitors are pretty hard to get. Will MKT X2 type capacitor work for these application? If not then any recommendation? Last time i used 100 ceramic caps (parallel on a bread board n connected through wire) and the heating was too little.

Thanks in advance. :)

Gabriel35

Tue Oct 02 2012, 08:13PM

Registered Member #2310 Joined: Wed Aug 19 2009, 08:04PM
Location: Santa Catarina - Brazil
Posts: 169

Hey!
What's your country?

MKTs will works, but Polypropilene ones will perform much better... This doesn't means that it can only be the X2 type, any well rated poly will work well.

I recommend something like 26x 220nF - 1000v caps...

The idea of using a variac in case the transformer sags too much is good, and surely it will sag, and you will ned the variac to crack the thing up...

45v already sagged, plenty of current is a good number, then you'll see the limitations of your circuit/traces/cooling... And this is pretty nice to do.

Probably if you have Well cooled Mosfets, and tank circuitry, and everything well built, you'll be able to push almost 1800w from the royer if using pairs of paralleled mosfets, ans something around 1200w I belive, using single IRFP260N's.

Keep us informed of your progress.
I hope to see photos of your work soon!

mohiuddinHimel

Tue Oct 02 2012, 10:44PM

Registered Member #4254 Joined: Sat Dec 10 2011, 09:36PM
Location: Dhaka, Bangladesh
Posts: 27

hi
Um actually from Bangladesh. I was planning to connect a large capacitance(something like 40,000uF 100VDC) as the filter cap because high current output of the transformer. I'll also connect a 50A relay between the large capacitor and dc bus. So that all that capacitance can get charged. When i'll press the trigger the relay will connect and the current will resonate.
After couple of minutes if it sags to much i'll release the trigger for couple of seconds allowing the filter cap to be charged again. :)

I've made two pretty large inductors from ferrite E cores. 19 turns each. Photos are coming soon.

Btw thanks a lot for the information. I was badly in need of those suggestions. To make it rough i was planning to use 40X0.1 uF X2 1000 volts capacitors as parallel bank...if you suggest i can go with 26x 220nF - 1000v caps too.

Mosfets will be water cooled directly connected to the copper pipe as Marko's design.

Looking forward to your opinion.

Here are the inductors i made out of ferrite E core and thick copper wire. 19 turns each.

got lucky and managed to get 38X100nF MKP r76 capacitors. and 4X56nF caps.

Gabriel35

Wed Oct 03 2012, 06:54PM

Registered Member #2310 Joined: Wed Aug 19 2009, 08:04PM
Location: Santa Catarina - Brazil
Posts: 169

Nice pics! Keep the progress...

Water cooled mosfets is a good idea too...
You can make the tank with 40x 0.1uF, this should work even better, since the currnt will be shared between more capacitors...

BTW Nice caps too!

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