I replaced the STP40NF10 Mosfets with STP55NF06 Mosfets. I moved the physical location of the mosfets to the center of the LC capacitor bank. Mosfets have been moved 2.5" closer to the capacitors bank center , 50% closer to the LC coil. WOW what an amazing difference. Both loads 1/4" and 3/8" steel rods heat up much faster than before. The mosfets I removed were rated 100v, 40 amps, .o28 ohms, the new mosfets are rated 60v, 50 amps .015 ohms.
Why such an amazing unexpected improvement?
I put a .4 ohm resistor in the +15 volt line, between the DC power supply and the induction heater circuit. With the circuit ON but no load I get a voltage reading of 1.22v across the .4 ohm resistor. With the circuit loaded using a 1/4" steel rod meter reads 4.4v across the .4 ohm resistor. With a larger 3/8" load I get 5.18v across the .4 ohm resistor. Power supply is 15vdc. I think I should be able to calculate total current in the circuit from this but I am getting crazy number?
With the .4 ohm resistor removed and my amp meter in its place, idle current is 6.2 amps for the circuit. With the 1/4" steel rod load current is 18.6 amps. With the 3/8" steel rod load blows the 20 amp meter fuse. No load frequency is still 89KHz but load frequency has changed from 64KHz to 74 KHz.
I am trying to determine how many total amps the circuit pulls with the larger 3/8" load?
Why such an amazing unexpected improvement?
I put a .4 ohm resistor in the +15 volt line, between the DC power supply and the induction heater circuit. With the circuit ON but no load I get a voltage reading of 1.22v across the .4 ohm resistor. With the circuit loaded using a 1/4" steel rod meter reads 4.4v across the .4 ohm resistor. With a larger 3/8" load I get 5.18v across the .4 ohm resistor. Power supply is 15vdc. I think I should be able to calculate total current in the circuit from this but I am getting crazy number?
With the .4 ohm resistor removed and my amp meter in its place, idle current is 6.2 amps for the circuit. With the 1/4" steel rod load current is 18.6 amps. With the 3/8" steel rod load blows the 20 amp meter fuse. No load frequency is still 89KHz but load frequency has changed from 64KHz to 74 KHz.
I am trying to determine how many total amps the circuit pulls with the larger 3/8" load?
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