Motor Under Voltage Protection Nuisance tripping
Motor Under Voltage Protection Nuisance tripping
(OP)
Hi All
we have fuel oil supply pump motor rated 90 kW to supply fuel to main boiler. this motor is supplied from grid, and unfortunately the grid is often faulted by lightning strike. after the fault happened, the voltage is decrease for a long time and recover again.But our motor have already trip because under voltage protection. the setting of under voltage is 0,75Un and time delay 9s.
I want to ask whether i can increase the time delay setting or simply block the protection so the motor will not trip because of this condition and what is the best practice for motor under voltage protection setting? because if the motor trip interlock to boiler trip system because of MFT(Main Fuel Trip) and it cost a lot to re- firing the boiler again. Thanks
we have fuel oil supply pump motor rated 90 kW to supply fuel to main boiler. this motor is supplied from grid, and unfortunately the grid is often faulted by lightning strike. after the fault happened, the voltage is decrease for a long time and recover again.But our motor have already trip because under voltage protection. the setting of under voltage is 0,75Un and time delay 9s.
I want to ask whether i can increase the time delay setting or simply block the protection so the motor will not trip because of this condition and what is the best practice for motor under voltage protection setting? because if the motor trip interlock to boiler trip system because of MFT(Main Fuel Trip) and it cost a lot to re- firing the boiler again. Thanks





RE: Motor Under Voltage Protection Nuisance tripping
1> Overheating.
2> Not enough torque to drive the load, which results in faster overheating.
3> When starting, not enough torque to bring the motor up to speed.
4> Drop-out or failure to pull in of contactors and relays.
Increasing the time setting is advice that we cannot give you without more information. If the motor is lightly loaded it may be acceptable. If the motor is heavily loaded you may trade a low voltage trip for an over temperature trip.
BUT
At 75% and 9 seconds I am surprised that relays and/or contactors are not dropping out.
You may be better served with an auto-transformer and contactors to automatically boost the voltage to the motor in times of low grid voltage.
Bill
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"Why not the best?"
Jimmy Carter
RE: Motor Under Voltage Protection Nuisance tripping
Sorry for my lack of knowledge on electrical power system, what do you mean by "relays and/or contactors are not dropping out" Is It unproper to set under voltage as low as 75% ? because I later found that our Medium Voltage Motor even set on lower value at 54% with 9s time delay.
RE: Motor Under Voltage Protection Nuisance tripping
RE: Motor Under Voltage Protection Nuisance tripping
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Motor Under Voltage Protection Nuisance tripping
RE: Motor Under Voltage Protection Nuisance tripping
Bill
--------------------
"Why not the best?"
Jimmy Carter