Hello all.
I'm new here. Just got one question regarding the motor starter. I have several induction motors which are used to drive the natural gas compressors. The motor hp ranging from 75hp to 150hp. Some of these motors use star-delta, soft-start and auto-transformer.
My question is that, among these three starters, which one is the best in terms of maintenance, cost saving and efficiency.
Thanks a lot for your help.
Cheers.

Hello andromeda


In terms of energy and efficiency, provided that all are correctly set up, the cost of operating the starters and motors will be the same, except that there are some hidden costs.
Star/delta starters have high starting currents when the starter switches to delta and these transients can be much larger than Direct on line starters. There can be electrical damage and interference resulting from these transients, and the torque transients can cause severe mechanical damage over a period of time also.
The soft starter should provide the best manintenance free operation for the starter, motor and driven load for the longest period of time. The soft starter would also generally allow for the lowest starting current, provided that it is correctly set up.

Best regards,
Mark Empson.