Get a suitable IPM or IGBT half-bridges - for 600A that's big and expensive.
If bare bridges you'll need IGBT driver chips, and opto-isolation or pulse-transformer isolation.
Serious and thorough attention paid to protection circuitry - you'll definitely need to active fast
over-current detection, undervoltage detection on the IGBT drivers (that's pretty standard),
shoot-through prevention in hardware (absolutely no question about this, many high-low drivers
give you this).
Do an awful lot of reading about the pitfalls of high power electronics, its not easy. At these
power levels there is danger of death and injury by electrocution, burns and explosion.
You'll need to make sure the driver can handle the stall current, which is probably larger than
the 600A.
And of course for a large series-wound motor you'll need a mechanical load to match, they are
never to be operated unloaded (did I mention explosion?).
There's a reason motor controllers of this size are usually commercial products.