How does system voltage affect the need for sinewave filters, dV/dT filters, or output reactors?

For 230-volt motors, it is rarely necessary to use an output filter since the motor will typically have the same insulation as a 460V motor. There is a significant insulation margin for overvoltage existing in the motor’s construction.
For 480-volt motors, consider the motor’s peak voltage design. Without filtering, the motor may see voltages exceeding 2.5 times the VFD DC bus voltage (or about 1700V) depending on factors such as cable length, size, type, and VFD switching frequency
For 600V motors exercise additional caution to prevent premature motor failure as voltage spikes will be 25% higher than on a 480-volt system