What is basic difference between Soft Starters And VFD
drives?

Answer Posted / naresh singh thakur engineer e

vfd means variable frequency it it is used where speed
variation is required it saves the energy also for example
we use vfd in air compressor when compressor is in load
mode motor runs at full speed & while compressor is in
unload mode the motor runs at its reduced speed up to 30 %
of full speed hence at this time energy saved.
we can achieve the speed above the rated speed & below the
rated speed using vfd the basic is the formula
NS = 120 * F / P
where ns = speed of motor
120 angle in electrical degree between two windings or coils
F = frequency which is to be varied
p= Number of poles
wher if no of poles = 2 fix
120 degree is fix
f= 0 to 70 above
put these values in formula & find results

while soft starters are the earlier version of vfd with
some less features than vfd

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