Replacing an AC drive in my mill and the use of a magnetic contactor in the power supply line
Usually you would use a motor protection device, or circuit breaker. Averything should be described in the operating manual, incudilng size, wire cross section,...
You would need a contactor if you need an emergency stop. It's up to you to decide.

You see, that 20 A is suitable for your inverter, not 30A.