Motor driver current snese protection

Do you have to measure DC levels? If not a current transformer might be an option. It's easier to clamp on the side of the burden resistor and when something really gross happens the core just saturates and the single turn primary almost becomes a wire.

Sounds doob-yuss.

Sounds expensive, and might 25V with 0.1R source impedance not potentially cause some major grief in the op-amp circuit?

An impedance (eg. a 10K 500V resistor rated at say 1W-- check the pulse ratings) in series with the 0.1R and put a diode or tranzorb on the other side of *that*.

Best regards, Spehro Pefhany

Then I'd also do that for the other side. In case that side goes open for some reason and the whole motor current would decide to flow through the measuring box and then ground instead, melting a few thing along the way, orange sparks flying and that sort of thing.

I wonder if putting a small sarcificial .5 ohm resistor on the collector of the top IGBTs would help the situation. If it blows open the rest of the circuit would fall to ground. Since it would be 5 times the resistance of the .1 ohm and physically smaller (say a 2010 vs Vishay WSR 2W) it "SHOULD" blow first. Kind if a fuse of sorts. The peak phase currents we're talking about here is 1.5A RMS. Duty cycle should be about 70%. Of course the 2010 resistors are typically limited to 250 max so at 500V would they just acrh across and short instead of blowing open. What I really need is a fuse. Are there SMT Fuse type devices around? Runs fine at say 3A continuous and pops when > than say ~10 amps is applied?

Maybe a thin trace in the PCB?

yes this motor runs very slow sometimes and a current sense transformer would have be very large to pass the signal. I was thinking along thise same lines.

I need something very small as my space is tight (as usual).

Of course you mean in series with the opamp input. As in: Between 0.1R and input.

robert

right. :)

Of course.

| +-||- ->|| 10K +-|| /| ___ | /+|--------+-|___|---+ -< | | | \\-|- V .-. |\\| - | | 0.1R | | | | | | '-' | | | +----------+---------- | GND

Best regards, Spehro Pefhany

Probably nothing SMT. At these current and voltage levels a fast trip is usually accompanied by molten solder and stuff flying about.

Noooo ....