What is different between DOL(Direct on line starter), VSD,
S/S(Soft starter), and A/T(Auto Transformer)

Answer Posted / vinod

dol--direct online starter.a contactor is connected across
the phase during the start.here the current will be more

VSD--VARIABLE SPEED DRIVE--they are actually used for speed
control.in some places they are used for starting
purpose,because the acleration can be programmed

s/s: they are made up of thyristors.each block prosuces a
modulated step by step input

a/t--they are also called as variac.the voltage can be
increased gradually through a cap.

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