Voltage Sag Affect on Motor Starters
Voltage Sag Affect on Motor Starters
(OP)
We had a voltage sag over the weekend. Our 13.8kv feeder dropped down to around 11.5kv
We then experienced lot of motor starters and VFD's that cutout.
When we went to restart everything, it was noticed that most of the dropouts was on newer equipment as opposed to older 35 and 50 year old starters. Anyone have an idea why the older equipment did not cutout.
We then experienced lot of motor starters and VFD's that cutout.
When we went to restart everything, it was noticed that most of the dropouts was on newer equipment as opposed to older 35 and 50 year old starters. Anyone have an idea why the older equipment did not cutout.





RE: Voltage Sag Affect on Motor Starters
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Voltage Sag Affect on Motor Starters
Bill
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"Why not the best?"
Jimmy Carter
RE: Voltage Sag Affect on Motor Starters
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Voltage Sag Affect on Motor Starters
Reference: NEMA ICS 2-2000 - Section 8.2
RE: Voltage Sag Affect on Motor Starters
RE: Voltage Sag Affect on Motor Starters
RE: Voltage Sag Affect on Motor Starters
"Will work for (the memory of) salami"
RE: Voltage Sag Affect on Motor Starters
I think this is the document Jeff mentioned.
They don't say anything about the dropout voltage. But we know it is somewhere less than the pickup voltage 80%dc and 85% ac
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(2B)+(2B)' ?
RE: Voltage Sag Affect on Motor Starters
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(2B)+(2B)' ?
RE: Voltage Sag Affect on Motor Starters
What is heart-breaking on wide-spread undervoltage situations is the find that the critical motor would have kept running had not some cheap pilot device quit at 80-90%.
old field guy
RE: Voltage Sag Affect on Motor Starters
Anyways, besides the coil dropout voltage, newer equipment is likely to have programmable digital protection relays with either a programmable or fixed low voltage trip. I wouldn't be surprized if something like 85% or 90% voltage was being used as the trip point.
The older equipment was likely relying solely on the coil dropout voltage for low voltage protection and that is why that equipment didn't trip.