Comment by londons_explore

Vce never really goes below 2 volts... Which for a 1000 amps means the running costs of the converter are 2000 watts * number of stages (~2800). 5.6MW of heat. That quickly dwarfs the purchase cost of those IGBTs.

Whereas the same calculation for MOSFETs [1] gives 4242 stages and an Rdson of 1.9 milliohms... = 8 Megawatts! Which sounds worse... But you can parallel the MOSFETs by spending double the money on them, reducing the loss to 4 megawatts... Or you can double it again to reduce the loss to 2 megawatts, etc.

When you run something 24*7, energy losses cost way more than capital costs - and MOSFETs let you make that tradeoff, whereas IGBTs do not.

[1]: https://www.infineon.com/cms/en/product/power/mosfet/silicon...