Electronic – High voltage and current

dc motorh-bridgehigh voltagehigh-currenthigh-side

I have a DC motor that needs and works nearly 400v and 20A. I chose FDL100N50 for n-channel mosfet also IXTK40P50P for p-channel mosfet.
I connect a 4n35 optocupler for output of every mosfet.
Are those suitable for this h bridge?

I couldn't find same caracteristics mosfet for n and p channel.

  • FDL100N50: 500v, 100 A, 2.5 KW , n-channel
  • IXTK40P50P: 500V, 40A, 890W , p-channel

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Best Answer

You cannot solve this problem of driving a 400V 20A motor using Pch MOSFETs. They do not exist with sufficient 600V Vds and $$Pd= (R_{dsOn}+DCR_{motor}) * I_{sc}²$$ (Isc=start current = start surge) for motor winding DC resistance, DCR causing worst-case surge current \$I_{sc}=V_{dc}/(DCR+R_{on})\$ (Ron of bridge = Rdson (Pch+Nch)).

Here your Pch is 350 mOHms and DC motors draw 8 to 12x rated current on startup. This means 400V/20A=20hms so while rated motor is 400*20A=8kW , surge power is 8 to 12x this if full acceleration or an average power draw of 80kW.

So you are planning to use a 5mA Optoisolator to drive a 80kW surge load. That will not work. Then the typ. full acceleration surge current is 200A²*RdsOn= 14kW means the mechanical guy or "you" have to design a heatsink for that surge power dissipation in the Pch for some period of time.

Now your Tesla race car driver is really in the hot-seat.

It MUST be a Quad Nch FET or IGBT full-bridge using the lower side for PWM to create a boost voltage to drive the high side Nch switches.

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