We're in kind of a bind at work and looking for easiest / cheapest way to load an AC generator (Synchronous permanent magnet machine).

We have access to a big 300A Mosfet module along with it's industrial gate driver.

I was wondering if I could rectify the output 3-phase voltage with big diodes such as these ones and then chop the power with the MOSFET into some power resistors.

The big question being : do I need some inductors (this?) to smooth out the current ? The motor main field inductance is > to 10µH.

And we're looking to chop around 100A @400VDC. The goal being of course to make the load vary form 0 to xx 40kW.

So to sum up our interrogations :

  1. Does this work? :-)
  2. Do I really need an inductor?

Down below is a crude schematic.

enter image description here

  • \$\begingroup\$ Your post is showing a little confusion. "100 A" isn't a measurement of power but rather current. Note that when you use the CircuitLab button on the editor toobar the editable schematic is saved inline with your post. No need for screengrabs, image uploads and background grid. In addition, we can copy your schematic and modify it in our answers. \$\endgroup\$
    – Transistor
    Mar 21, 2019 at 11:12
  • \$\begingroup\$ Hi Transistor, Sorry for the little confusion, I removed the power which was misplaced. Noted for the Circuitlab button for next time. \$\endgroup\$ Mar 21, 2019 at 11:41
  • \$\begingroup\$ I also forgot the diode in order to recirculate the current when the switch is opened... \$\endgroup\$ Mar 21, 2019 at 11:41
  • \$\begingroup\$ Can you elaborate a bit about why you need the inductor? It looks to me that it adds problems, resistive loads are usually the easiest to drive. \$\endgroup\$ Mar 21, 2019 at 12:35
  • \$\begingroup\$ Hi Vladimir, As you ask, I'm realising that it would be needed for a buck (current smoothing on the output) but definitely not for a DC load as I drew it. Nevertheless, should I want to "smooth" the current before the switch, could I maybe add a big CAP to do so? \$\endgroup\$ Mar 21, 2019 at 15:38


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