Po co low volt

[ctaylo360860]

Update:
Po co had a bad tap on the primary stop the substation… they changed it out and my transformer went up to the correct voltage.

also had them tap the other transformer we have on site back down because we were getting 502 phase to phase on the three phase side and 253 once we stepped it down with. Idk if 128volts on a regular receptacle would cause harm.

now we have good voltage everywhere 480 with load and 120/240 on the single phase side

 

[Jraef]

A standard NEMA designed 460V rated motor should preform fine down to -10%, so as low as 414V. The quality of your motor may mean they did or didn’t adhere to NEMA standards, but generally, responsible mfrs selling into this country do.

A separate issue is the fact that this is on a VFD. The VFD cannot create voltage but it will be capable of adjusting to a change in voltage. When you program the VFD to put out 460V to the motor (by programming the VFD with the motor nameplate data), if the line side is anything more than 460V, it is going to maintain the 460V out to the motor anyway. If the line voltage goes BELOW 460V, the VFD will limit the maximum speed that the motor can run at while maintaining full torque on the load by maintaining the correct ratio of voltage and frequency. So for example a 460V 60 Hz motor has a V/Hz ratio of 7.67:1. So if the line voltage drops to 454V, the drive might need to drop the speed proportionately. 454/460 = .987, so the maximum speed the VFD would run at would become 59.2Hz, but only IF the motor needed full torque. If the motor was only loaded to 90% of its capacity, you may never see an issue.

 

[ctaylo360860]

A standard NEMA designed 460V rated motor should preform fine down to -10%, so as low as 414V. The quality of your motor may mean they did or didn’t adhere to NEMA standards, but generally, responsible mfrs selling into this country do.

A separate issue is the fact that this is on a VFD. The VFD cannot create voltage but it will be capable of adjusting to a change in voltage. When you program the VFD to put out 460V to the motor (by programming the VFD with the motor nameplate data), if the line side is anything more than 460V, it is going to maintain the 460V out to the motor anyway. If the line voltage goes BELOW 460V, the VFD will limit the maximum speed that the motor can run at while maintaining full torque on the load by maintaining the correct ratio of voltage and frequency. So for example a 460V 60 Hz motor has a V/Hz ratio of 7.67:1. So if the line voltage drops to 454V, the drive might need to drop the speed proportionately. 454/460 = .987, so the maximum speed the VFD would run at would become 59.2Hz, but only IF the motor needed full torque. If the motor was only loaded to 90% of its capacity, you may never see an issue.

The drag motor that’s running isn’t on a vfd. This read out is on a bucket that has a vfd in it but currently it’s not being used. The read out a week ago was 462volts. The po co changed a primary adjustable tap at there substation and it ended up Raising the voltage from 462 to 482….. my city looses power or has a flash probably everyday out substation infrastructure isn’t good. I feel bad for the lineman because all they can do is repair things until they spend the money and fix the big problem

the other poco transformer I had them tap up and we were getting 492 but after they made the fix it jumped up to 503…. Wasn’t to worried s out the motor loads, but we have a plc control panel and computers on the 120/240 side. I wasn’t sure if the computer or plc equipment would like 253/128volys so I had them tap it back down. Now it’s at more of a standard voltsge. 480 phase to phase 277 phase to ground, and then the single phase pane after it’s stepped down is At 120/240volt