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Registered Member #3964
Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332
Sulaiman wrote ...
If your gate drive transformer could handle the volt.seconds required to operate the irf's then it will not change due to using the ixys transistors, since the drive voltage and frequency will not change significantly, and the resistance of the gdt windings are negligible. so I'm fairly sure it's not the gdt, more likely the gdt driver (ic or discrete) or the resistor(s) effectively in series with the gates (any primary or secondary series resistor) are too high value.
I've replaced the GDT as my first suspicion but it is not the problem, :/ didn't check the gate resistor, probably will do it tomorrow..
I'm using discrete circuit (P+N: IRF9530 + IRF640N) MOS channel on the output, but i don't know what particular & possible errors i might have done on this side. Could you site some? :)
UPDATE: My bridge is supplied by 230v/60hz mains pass thru a single diode (positive) and the neutral for (negative) => unfiltered.. no electrolytic installed to see some straight sparks. and my interrupter is synced with the mains, e.i. says go whenever the positive half cycle are charging the bridge.
NOTES: 1. when i put some filter caps. (~300uf) the system is working fine.. (by fine i mean, corona are visible ~4inch branchy sparks) synced with the interrupter @ any BPS rate. 2. but when i removed the filters, the same problem occurs, (i.e. no corona sparks if BPS is less than 45hz or something)
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
don't know what your circuitry is, so guessing;
if there is NO capacitance across the DC Bus for the output bridge then . at 10's or 100's of kHz the impedance (e.s.l.) of the supply would be enormous . the 10's or 100's of kHz signal will find the utility mains supply a quite good antenna/radiator
whether or not you use electrolytic(s) across the DC Bus it is a good idea to use low e.s.r. capacitors (e.g. polypropylene film, as used for mmc) of as much capacitance as you can spare/afford, to provide a low impedance supply at hf. (good electrolytics seem to work to a few 100's kHz, but some are rubbish even at 100 kHz)
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MOSFETs and their differences
