On Sun, 11 Jan 2009 11:18:53 -0800, Admin wrote:


Hi all,

I have this circuit that I am hope to use for HV electrolysis. It has
damaged every Mosfet and IGBT I have tried. It even damaged an IGBT
that is rated 600V and 58 amps. The circuit works without a hitch when
the load is resistive like a light bulb.

But as soon as I hook up a transformer the IGBT fails in 10 seconds. It
has trouble with inductive loads.

I have tried clamping the IGBT with a diode to no avail.

Please, somebody take a look and tell me what I am doing wrong. My
power source is and auto inverter.

Where to begin?

The gate driver is seriously wimpy, unbypasses zener 12-volt thing,
weak opto pullup and weaker passive pulldown. Slow edges make for high
dissipation. You need a serious gate driver, like an LM5112 or some
such.

Is the transformer saturating? The slow gate drive may contribute.

Why such a tiny post-rectifier filter cap?

What's the operating frequency and pulse width?

Why use a transformer at all?

What's it all for, anyhow? Electrolysis is absurdly inefficient at
high voltages.

John