Motor Starting
Motor Starting
(OP)
We have LV motors on 12.47kV utilty. Motors started at no load. Is 10% voltage dip at utility bus generally acceptable when motors are started?
Also if soft starter is used with ramp set to 10 seconds and inrush current limited to 400%, the voltage dip at utility bus is improved by only 2%. Is it worth it to use soft starters in this case?
Also if soft starter is used with ramp set to 10 seconds and inrush current limited to 400%, the voltage dip at utility bus is improved by only 2%. Is it worth it to use soft starters in this case?






RE: Motor Starting
RE: Motor Starting
As to the soft starters being worth it for a 2% improvement, in my opinion soft starters are "worth it" for a variety of reasons beyond reducing voltage drop. But 8% VD is still beyond acceptable if that is your only consideration. However, will your motors start at 350% or maybe even 300% and possibly bring that down to 5% or less? In your situation, turn the ramp time to zero and just go into current limit immediately, ramping will not help you with this situation. Do you already have the soft starters or are you modeling this in SKM or ETAP? If modeling it, just base it on the current limit, forget the ramp time.
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RE: Motor Starting
In any case 5% it is maximum acceptable at common utility medium voltage network.
But I don't understand how reducing the start current from 600% to 400% only 2% difference in voltage drop is measured.
RE: Motor Starting
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Motor Starting
RE: Motor Starting
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Motor Starting
RE: Motor Starting
Have entered the correct inertia data?
RE: Motor Starting