In the figure below, presented in the manufacturer datasheet, you can see the Ic-Vge curve of an IGBT device. As mentioned, it has been drawn at Vce=20V. What does this equality mean? Can we have such a high voltage for the parameter Vce when turning the IGBT device on?
Vce=20V means that in this case the presented curve is made when collector-emitter voltage equals 20V.
To see if 20V is or is not too much, take the datasheet and find table named "Maximum rated values" and check for parameter named "collector-emitter voltage". See example below:
In many cases this voltage can be high, as the IGBT's are widely used to switch high voltages and currents (for example AC motor drivers).
The Vce = 20 V means that 20 Volts DC is applied across the device between Collector and Emitter.
This curve gives us an indication of how much current the device will allow to flow given a high enough Vce. If a much lower value of Vce was used, for example 1 Volt then that low voltage could prevent a high current from flowing.
You cannot just look up a point on the curve and operate the device at that point for some time. For example: at Vge = 10 V, the device will typically allow for 75 A to flow. So that's 75 A through the device while Vce = 20 V, that's 75 A * 20 V = 1500 W, that's a lot of power and a lot of heat will be generated.
That's why usually this measurement is done with a short pulse so that the device gets almost no change to heat up.
Under normal operating conditiond, when you turn on the IGBT then normally the Vce voltage would become much lower, it would "collapse" as soon as the IGBT turns on because current would start to flow so a voltage will develop across the load. That then decreases Vce and power dissipation decreases dramatically.
