What is basic difference between Soft Starters And VFD
drives?

Answer Posted / ramamoorthy

VFD : VFD serves two purpose(smooth starting and speed
control):
a. Smooth starting by gradually increasing the source
power to rated output (by maintaining V/F ratio).
By starting at zero frequency & zero voltage (thus
the starting current also) and gradually increasing
the same to rated value.
b. Controls speed not only during starting but also at
rated voltage.

Soft starter serves only one purpose (Smooth
starting):

a. Smooth starting by gradually increasing the source
power only by increasing the voltage from zero
to full voltage and not varying the frequency like
autotransformer.
b. Cannot control speed at any point of time.

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