What is the purpose of having passive filters in inverters?

Passive filters are made up of any combination of resistors, capacitors, and inductors to filter out specific ranges of frequencies.

PWM, meaninig Pulse Width Modulated, is a form of output from a switching device like an inverter. The switching devices turn ON and OFF at a set frequency, called the carrier frequency. The time the switch is ON versus time OFF determines the average Voltage seen at the output by the load, like a motor. Inverters are the switching devices that convert DC into AC. Many loads or distribution systems have negative impacts from the high frequency switching of PWM machines. The outputs usually require filters to smooth out the PWM signal before it gets to the load. Long motor leads do not like PWM signals due to the capacitive impedance that cables have. Output filters on an inverter "smooth" out the signal and protect the cables. No, passive filters are different from EMI filters. EMI filters are usually used to prevent interference from outside a device or circuit while a passive filter functions for things within a circuit.