What is vfd called as variable frequncy drive?
VDF is variable frequency drive.In AC (alternative current) induction motors the speed is obtained by parameters like poles and frequencyformula Ns = 120 x f/ pwhere N= (synchronous ) speed rpm of motor. F = frequncy Hz of the power supply ex:50Hz, 60 Hzto obtain variable speed of the motor by changing the frequncy it is achived with the help of VFD device.