Gate drivers for IGBT inverter: How to isolate V supplies?

[THRILLHO]

This video describes my issue pretty well (I have it set to start when he talks about my specific situation):
ETA: looks like the board doesn't allow the video to start at the specific time, the important stuff begins around 5:30


Our applications are a bit different as his design is for single phase applications, but the problem remains the same for both cases:

This is for a 3 phase variable frequency drive. An Arduino will use PWM to control the inverter. I'm going to have a gate driver on each of 6IGBTs. I need one ~18V DC source for the lower 3 IGBT gate drivers (this is kosher, will not cause a short), but then I need 3 more for each of the three upper IGBT drivers. We have one transformer dropping one of the 265V phase lines down to 24V, which I was then rectifying to use as a DC voltage supply for wherever necessary. That gives us one of the four sources needed to run the inverter. Using three separate batteries to provide the other sources would be really sloppy, bulky, and expensive. Same goes for using a single phase to three phase transformer + more rectifiers. I stumbled upon gate drive transformers and thought that I had a solution, but all of them appear to be for really high frequency applications (400khz+), which is no good for a VFD that will need to output 1-100hz signals. I'm kind of at a loss as to how to make this work and would appreciate any advice. Thanks.

 

[milesyoung]

I'm going to have a gate driver on each of 6IGBTs.

Unless you absolutely have to do this, then save yourself the trouble and get either a full three-phase driver or three half-bridge drivers. You'll then only need two non-isolated supplies, and you won't risk shoot-through of your IGBT module(s), since you won't be the one controlling the dead-time.

Here are some examples:
International Rectifier General Purpose Gate Driver ICs

 

[Windadct]

I agree with Miles - look for a dual 600V driver or a full 6 channel chip . They will help set deadtime and will have bootstrap circuit for each of the 3 high side circuits.. also the driver needs to be sized to the type of IGBT - generally not a problem for experimenter, but if you bought some large surplus IGBTs this should be checked

You are getting 6 PWM channels out of an arduino - which model? - noting for 0-100 Hz output you want ~20 X Fsw ( 2 khz) . Most of the basic models(328) only have three timers and they are all slightly different, one sits on the serial port! You can not do complimentary switching (i.e. three timers to 6 channels PWM)-- without some external logic - for a 3 phase AC case.

 

[THRILLHO]

Thanks you two. I didn't know that all-in-one three phase gate drivers exist. Very convenient that they require only one power source. Saves me a lot of time, space, and money.

 

[Windadct]

As a question Thrillho - which arduino are you using? I am am curious about your 6 channels of PWM.