Induction brass annealer redux

[jeffo1960]

Pic

 

[itchyTF]

There is a lot of reading here but it may be helpful.

1000 Watt 12 to 48 Volt ZVS Induction Heater Troubleshooting Guide

I have destroyed and repaired several of these 1000 Watt 12 to 48 Volt Induction Heater boards. In this webpage I explain how I repair them.

spaco.org

Click on "Go back to ZVS stuff" for more info. He seems to be focused on heating steel but did have links on heating brass.

 

[jeffo1960]

Did not see anything regarding the problem i got

 

[renn]

I just got my induction board and found one of the caps was not soldered on properly. I touched up on all the joints after I discovered the loose cap.

 

[jeffo1960]

Think i have found out the problem,there is no insulating pad behind the FETs, i separated the Fets from the heatsink and i have not got continuity,now will thermal paste,be ok to put there.Or do i need something like this TO-220,as if i got it correct it goes in-between the screw and the heatsink, or is there anything else i can use,Thanks in advance.

 

[itchyTF]

Think i have found out the problem,there is no insulating pad behind the FETs, i separated the Fets from the heatsink and i have not got continuity,now will thermal paste,be ok to put there.Or do i need something like this TO-220,as if i got it correct it goes in-between the screw and the heatsink, or is there anything else i can use,Thanks in advance.

If there is metal exposed on the back of the fet you can't rely just on thermal paste to act as an insulator. I'd either use mica plus paste or one of those thermal insulating pads.

 

[jeffo1960]

Thanks for that appreciated for all the help I am certainly learning things

 

[itchyTF]

Those FETs are not TO-220. They are TO-247 if they are IRFP260.

 

[jeffo1960]

Thanks for that

 

[jeffo1960]

I've put pads between the Fets and heatsink, and got no continuity now, so that's all good, but still drawing 17amps without any thing in the coil, any help would be much appreciated

 

[itchyTF]

I've put pads between the Fets and heatsink, and got no continuity now, so that's all good, but still drawing 17amps without any thing in the coil, any help would be much appreciated

That link I provided in post 2,662 has some troubleshooting tips. Might try those to see if that helps.

 

[jeffo1960]

I done the tests on the link you posted, and all seems OK, provided I done them correctly which I think I did, I have checked all my wiring and can't seem to find anything wrong, but obviously there is somewhere
Thanks again

 

[jeffo1960]

It starts at 7amps then jumps up to 15 tryed to post a video but failed

 

[itchyTF]

As an experiment try winding a coil with about 1 micro Henry (uH) using the formula in post 2,559. Use just solid 12 ga copper wire so not to waste tubing. As I previously mentioned, when I used the large coil supplied with the board it only drew about 5 or 6 amps. But when I used a smaller coil with less inductance it drew around 15 amps with nothing in the coil.

 

[itchyTF]

It starts at 7amps then jumps up to 15 tryed to post a video but failed

Sounds like something might be breaking down.

 

[jeffo1960]

I looked at that formula it is above my understanding

 

[itchyTF]

I looked at that formula it is above my understanding

Send me the inside and outside diameter, number of turns and length of coil from top to bottom.

 

[oliverpsmile]

I looked at that formula it is above my understanding

Either the bloody board is busted or you have short in the coil. Try with the original coil. If the current is normal (5-6 amps) the board is OK.

- Short in the coil - when adjacent turns touch each other.

 

[jeffo1960]

I cut the original coil wish I hadn't now,the wraps in the coil are definitely not touching

 

[oliverpsmile]

Your coil geometry is correct and if you do not have short before the coil (i.e fittings, heavy metal parts or else) the board is busted. It happens when the board is energized (48 volts) without coil connected. Get another board.