I've been messing around for a couple days with this 2DI50D-100 power module that I got out of an old Italian VFD that I got dismissed at work (I'm an electrician) because it stopped working.
This is the schematic that's attached to the device itself:
Basically, I'm trying to couple two of them into an H-bridge to drive a 180 V rated DC motor.
First of all, I tried to make the high side work, with just 24 V, just to do some tests. So I connected the power supply between C1 and E2 and the motor between C2E1 and V-.
To turn it on I just connected C1 to B1 through an ampmeter. The motor ran just fine and the multimeter showed 4 mA so we're all good (are we?).
Then I wanted to do the same test with the lower side, so I powered the module between C1 and E2 like before, latched the motor between V+ and C2E1, and to turn the module on I connected the ampmeter between C1 and B2. I expected it to work exactly like the first test.
Instead, I got some sparks and obviously the current limiter kicked in. I thought the lower circuit was gone, so I did the same test on all three modules; same result.
So, why does this happen? Isn't the lower circuit an exact copy of the upper one? Shouldn't it work the same? Am I missing something or are the lower sides of the modules broken?
Oh, by the way, I fried one of them.