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Registered Member #2063
Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352
ok so, today i just wound another secondary coil with 200 turns of 1mm thick copper wire. it fitted on the same core with same primary coil, ran my ZVS driver at 37 volts from 3 lead acid batteries at 18AH each. i measured the current of the secondary with a diode from a microwave oven and an analog amp meter, i was only able to get around 400 mA. why so low with such thick wire?
Registered Member #3595
Joined: Mon Jan 10 2011, 04:46AM
Location:
Posts: 26
haxor5354 wrote ...
ok so, today i just wound another secondary coil with 200 turns of 1mm thick copper wire. it fitted on the same core with same primary coil, ran my ZVS driver at 37 volts from 3 lead acid batteries at 18AH each. i measured the current of the secondary with a diode from a microwave oven and an analog amp meter, i was only able to get around 400 mA. why so low with such thick wire?
Thicker wire doesn't equal more power output, just more current capability - increasing the size of the wire just lowers resistive losses. The thicker wire also gives you less space, letting you wind less windings, outputting less voltage at a higher current - is that what you are trying to do?
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
haxor5354 wrote ...
ok so, today i just wound another secondary coil with 200 turns of 1mm thick copper wire. it fitted on the same core with same primary coil, ran my ZVS driver at 37 volts from 3 lead acid batteries at 18AH each. i measured the current of the secondary with a diode from a microwave oven and an analog amp meter, i was only able to get around 400 mA. why so low with such thick wire?
What was the voltage? You can only transfer just so much power with a given core and drive. More turns on the secondary will give you higher voltage at lower current. Fewer turns will give you lower voltage but allow higher current. Heavier wire reduces the resistance, reducing the copper loss which gets more significant at higher current. Parasitic inductance, capacitance, and the core gap all have a dramatic effect on the results too. You will get the most output at any of the various resonant frequencies. If you are using a flyback drive, you need a gapped core. For push-pull you will generally get more power without the gap but you have to be careful not to saturate it.
One advantage flyback mode has over push-pull is that the output voltage has little relation to the turns ratio and is mostly determined by the flux level in the core and how quickly it collapses. I was playing around with some small gapped ferrite cores salvaged from 100W SMPS boards and with 20:200 turns I was getting several kV from a 20V input with enough current to melt the end of the wire into a ball. I just fiddled with the frequency and duty cycle until the core was just below the onset of saturation.
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homemade flyback transformer
