Post by: Luke on April 16, 2017, 05:58:42 PM
I used she Schematic from kaizerpowerelectronics.dk.
My parts are:
2x IRFP260N 200V 49A
2x 470E 4W
2x Z-Diode 1,3W
2x BYV26E Si-Diode
2x 10kE
2x 2,2uF =4,4uF MKP 250V
2x 64uH, but only 5A
My circuit doesn’t work, I suppose it does not oscillate.
For the Power Supply I use two 3S LiPo serial -> 25,2VDC 135A constant (157A Burst), 3,4kVA.
To protect the circuit I use 40A car fuses.
I built several workingcoils the last has 7 turns of 6mm².
I think the chokes are to small.
Would it suffice to wind the ferrit cores with a bigger cable?
How should I switch the circuit on?
In the picture you see the first build-up with other transistors and the capacitors are located on the board.
In the last build-up the capacitors are located on the workingcoil.
Thanks,
Luke
Post by: Mads Barnkob on April 17, 2017, 07:24:38 AM
Did you calculate the resonant frequency of your LC circuit, you did not write down all the parameters on the work coil, but I assume it is a helical coil, you could use my helical coil calculator and insert the tank capacitance too, to get the resonant frequency. http://kaizerpowerelectronics.dk/calculators/helical-coil-calculator/
You choice of components, perfboard etc is good enough for a small IH, but be aware that trying to conduct 10-20 A from the supply and hundreds of A in the resonant circuit is not going to end well with these small boards, good that you moved the capacitors to sit directly on the coil. Just be sure to mount them correctly for even current sharing, see here: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/dc-bus-capacitor/
Did you 40A fuse blow at any time? I think not, if you have a smaller one, like 20A try that instead, but a melting fuse is actually too slow to protect a MOSFET, they will explode before the fuse burns.
I do not think your chokes are too small for a small IH
Switching the circuit on is giving it full voltage from the start, ramping up the voltage can be fatal due to unknown state of the MOSFETs when the voltage gets below 10 VDC, there is a high risk of damaging the MOSFETs there.
Post by: Luke on April 17, 2017, 01:31:27 PM
The result of the calculation is with 5 turns 81kHz and with 7 turns 65kHz.
Yes, the fuses blow anytime. Thereby I think the chokes are too small, because they got warm last time as the fuse broke.
Post by: Mads Barnkob on April 18, 2017, 01:54:45 PM
Are your MOSFETs destroyed after fuse has blown and the chokes heat up? Did you measure the voltage of the battery pack drop below 10VAC when connected? I have not used batteries to feed a Royer IH with yet, but unless it is large car batteries, you could have problems with voltage drop due to too high load?
If the 3S LiPo is only two small batteries, then this is most likely your problem.