Motor Trips During Voltage Sags
Motor Trips During Voltage Sags
(OP)
We have a problem of motors trips during voltage sags although their contactors are equipped with ride through circuit or the control supply is fed from constant voltage transformers. My question is "Has anyone experienced the same problem? Also, if yes, is there any way to test the time contactor holds? The sag was of short duration (4 cycles) yet some motors tipped.
Your help will be appreciated.
Your help will be appreciated.
Jaafar Al Sheef
Saudi Aramco
Saudi Arabia





RE: Motor Trips During Voltage Sags
To test the drop out time of the contactor you'll need a high speed recorder, watching the voltage and the contact parting time. (Likely main contacts isolated for test equipement)
RE: Motor Trips During Voltage Sags
RE: Motor Trips During Voltage Sags
Can you determine if the sag from transformer or cable impedance? Your only solution may be a stiffer circuit.
RE: Motor Trips During Voltage Sags
1. To find the cause of voltage sags and eliminate them.
2. If 1. is not possible, then an alternate power supply will be needed, perhaps working in conjunction with a static transfer switch that can transfer the preferred power supply to the alternate power supply within a quarter of the cycle. Also, the DC controls could get some consideration.
RE: Motor Trips During Voltage Sags
RE: Motor Trips During Voltage Sags