Re: [CAD_CAM_EDM_DRO] Re: H bridge progress

Lee Studley wrote:

> Thanks Jon,
>
> I wondered what those inductors were on the picture of
> your servo amp. I thought they might be a chopping/pulse sensing
> arrangement for the current limiting circuit. IGBTs are fine
> for this application and yes I'm driving them hard and controlled.

I just use a low-inductance resistor for current sensing. The fault
sensing is on the high side, so it can detect a fault to ground, which
would be missed by the typical low-side current sensing.
I also have another low-inductance resistor in series with one of
the motor leads, and read out the voltage across it with an instrumentation
amplifier for current feedback in the torque loop.

Jon