RE: TI Hercules RM46 Three-Phase Generator With Transformers Part 1

jc2048 — Tue, 13 Jun 2017 10:01:07 GMT

Good project. I'm looking forward to the further parts.

There is a small problem with the circuit you show, though, and it could be improved.

Here's the 'shoot through' current in one half of the bridge when the PWM changes state. (This is from a simulator, so reality will be a bit different, though I'm finding that MOSFET models do seem to be fairly good.)

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That occurs because the MOSFETs have considerable gate capacitance and the time constant (in conjunction with the pull-up resistor) for moving the gate up is much different to pulling it down with the transistor, so there's a small period of time when both are conducting. (Try it with a simulator, looking at the gate voltages, to get an idea of what's happening.) The effect is also quite different with the two edges of the PWM because of the lack of symmetry with the drive.

The circuit works on the bench because these MOSFETs can take that sort of current when pulsed (it's only for a few uS), the 60Hz repetition rate is very low (so the dissipation is low), and the PSU is designed for 30A (and, presumably, doesn't dip too much).

RE: TI Hercules RM46 Three-Phase Generator With Transformers Part 1

balearicdynamics — Mon, 12 Jun 2017 04:58:15 GMT

Sounds a good project with solid bases. Despite the correctness I can't evaluate I appreciate your details in this project premises and the theory explained. I will follow this work, it sounds I can learn a lot from your job and the comments and suggestions. Thanks for sharing.

Enrico