Voltage and current need to be controlled: 85V 50A ( I want to control
the current from 0A to 50A as required by the application).
This doesn't side like a problem that is conveniently solved by an IGBT (or MOSFET for that matter). You wish to control voltage and current to a load it seems but, when the voltage is (say) at the halfway point (42.5 volts) and the current into the load will be 25 amps (assuming a linear load resistance), the power dissipated by the device will be 1062.5 watts and that's a lot of heat to get rid of.
So, unless you have a cunning plan that involves water cooling the transistor I would suggest you walk down the path towards using a high-power buck regulator. Even then, it's not likely to be better than 95% power efficient so, you might expect to have to deal with a heat power dissipation of 50 watts. However, this can be solved by decent heatsinking and possibly a fan.
@Andyaka. This circuit is just a dummy load... It won't supply power
to any other circuit/device.
If it's a dummy load, your power dissipation is going to be 85 volts × 50 amps = 4250 watts. That's 4 times greater than what I stated earlier. If you insist on going down the IGBT route here's the type of problem you could easily face that can leave you with dead devices and a lot of head scratching. Consider the IXXN200N60C3H1 from IXYS just as a quick example of something that you might come across. It has decent enough ratings: -
However, the devil is in the detail such as this graph: -
I've added the coloured lines and text. As you can see, at 85 volts and 50 amps, you cannot operate the device for any longer than about 3 or 4 ms. In other words, not much of a dummy load for continuous operation.
But it does get worse than that regarding the control of the gate voltage and collector current; if your 85 volt supply is capable of delivering hundreds of amps, using an IGBT like this (intended for switching applications) but in a linear application then you run foul of thermal runaway. Look at this graph: -
At 25° C you nominally need to drive the gate with about 8.6 volts (with respect to emitter) to achieve 50 amps collector current. Then, as the device inevitably rises in temperature (very, very quickly on the die of the device) the current can rise to 70 amps in a few milli-seconds and, unless your feedback circuit is very, very quick at responding, you'll end up with a dead device in maybe less than 20 milli-seconds. The problem here is that the body of the IGBT won't even feel warm to the touch and, no amount of heatsinking would have saved the day.
It's up to you what route you go but, I bet that the least-painful route is not linear control.