Answer Posted / sbb
VFD is defined as "Variable Frequency Drive". The main
purpose of VFD is to control the speed of the drive for
different applications.
The principle behind that VFD as we know that N=(120F)/P:
Where N=Speed
F=Frequency (Indian Freq. 50 Hz.)
P=Poles of motor.(Constant)
So speed is controlled by varying the poles of frequency,but
poles is constant and it will be designed when motor is
manufactured.but we can change the frequency though
PWM,Cyloconverters and by thyristor controlled circuits.
So for AC, speed control through VFD is by V/F controll.By
controlling Voltage or by Frequency or by both we can
control the speed.
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