Po co low volt

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ctaylo360860

ctaylo360860

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We have a 3phase 277/480 wye system. The voltage seems very low for me and I was told by Po co that the transform is tapped out... yesterday while running one- 40hp motor the voltage dropped down to 462volts. I’m worried if we really get the plant running we’re going to drop lower that harming equipment... do you think I have reason to be concerned or should the impedance in the motor be able to handle somewhat lower voltages? If I should be concerned is there something I can do or is it just my city power grid is tapped out?

1st pic is of mcc giving idea of load we can draw

3rd picture is voltage reading from mcc with one 40hp motor running.

2nd picture shows voltage with no motor loads running just some equipment inside mcc and lights in panel room.
 

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infinity said:
I'm pretty sure that any motor rated for 480 volts will operate just fine on a system with an output 460Y/265 volts.
Click to expand...
Say we are running the 40hp drag, and we also need to run out 100hp auger motor. Will the load draw the voltage down low enough to actually make the motors or equipment work much harder?

or would that come down to the impedance of each individual motor
 
infinity said:
I'm pretty sure that any motor rated for 480 volts will operate just fine on a system with an output 460Y/265
Click to expand...
This is the opposite instance what is higher voltage inwhat about a motor that is 460 on name plate and has Po co transformer has a secondary voltage of 492. The 460 rated motor should be fine recieving higher voltages of 492v correct?

It looks like higher voltage may have larger inrush current . But once motor gets to full load current this should make the motor operate more efficiently?

Thanks again for the replay always appreciate the help!

Is there any benefit to having the secondary with higher voltages than lower?

example the voltage at poco transformer a was 477 they tapped it up to 492. This transformer has a 150hp motor load that runs frequently. Would it be better to have the voltage lower or st 492?

transformer b which has its own riser and feed is maybe 100 ft away from transformer a. The voltage here with no load is 478 and bouncing... the transformer is tapped all the way at transformer a and b but the voltages are 14 volts in difference with Litte to no load running. What would be causing this ?
 
infinity said:
I'm pretty sure that any motor rated for 480 volts will operate just fine on a system with an output 460Y/265 volts.
Click to expand...
I have never seen a motor with a nameplate voltage of 480. The current ones have a nameplate voltage of 460, and the older ones 440.
It should be able to run fine with a voltage of 5% below the nameplate.
 
ctaylo360860 said:
This is the opposite instance what is higher voltage inwhat about a motor that is 460 on name plate and has Po co transformer has a secondary voltage of 492. The 460 rated motor should be fine recieving higher voltages of 492v correct?

It looks like higher voltage may have larger inrush current . But once motor gets to full load current this should make the motor operate more efficiently?

Thanks again for the replay always appreciate the help!

Is there any benefit to having the secondary with higher voltages than lower?

example the voltage at poco transformer a was 477 they tapped it up to 492. This transformer has a 150hp motor load that runs frequently. Would it be better to have the voltage lower or st 492?

transformer b which has its own riser and feed is maybe 100 ft away from transformer a. The voltage here with no load is 478 and bouncing... the transformer is tapped all the way at transformer a and b but the voltages are 14 volts in difference with Litte to no load running. What would be causing this ?
Click to expand...
You've never seen voltages lower than those? Those are real-life figures. Stop overthinking there.
 
don_resqcapt19 said:
I have never seen a motor with a nameplate voltage of 480. The current ones have a nameplate voltage of 460, and the older ones 440.
It should be able to run fine with a voltage of 5% below the nameplate.
Click to expand...
The motors I have say 460 on the name plate. there are two transformers at the site. One that has a voltage of 492. When 150hp leg is running voltage drops down to 488.
The other transformer has a voltage of 467, and it was dropped down to 462 with 1 40hp motor running.
So does that 5% go For higher voltsges as well?
 
Hv&Lv said:
456v would be below ansi
Click to expand...
topgone said:
You've never seen voltages lower than those? Those are real-life figures. Stop overthinking there.
Click to expand...
My company bought the plant not long ago and I have been on site two days... Previous plant manager said electrician told him numerous time that voltage was too low and it was going to burn something up. How far low it got I don’t know yet because the only real load we have ran on the system is a 40hp motor there are pry 20 other buckets. My poco is know for having problems there substation is shit... I just seen a house that had 97 bolts because they had the transformer way over loaded on that block...
So I should wait till I have a for sure problem to get some understanding on the subject? How low should I let the voltage drop before I get worried?
 
Thought time: If a dual-voltage motor is rated 208-230/460v, isn't it really rated 208-230/416-460v?
 
ctaylo360860 said:
The motors I have say 460 on the name plate. there are two transformers at the site. One that has a voltage of 492. When 150hp leg is running voltage drops down to 488.
The other transformer has a voltage of 467, and it was dropped down to 462 with 1 40hp motor running.
So does that 5% go For higher voltsges as well?
Click to expand...
All motors have utilization voltage stamped on their nameplates. That will be the voltage measured at the terminals of the motor. When the utilization voltage says "460V", that means it will be very happy running at -5%. NEMA even requires manufacturers to make induction motors that can work fine with a 10% voltage variation, and a 6% limit on universal motors.
 
462 volts where? At the service? At the motor?

If the voltage is lower due to feeders or branch circuits, that's not the utilities fault.

Here is one standard for utility service voltage tolerances, so it looks like you are well within that:

Voltage Tolerance Standard – ANSI C84.1 – Voltage Disturbance

voltage-disturbance.com

If you are really worried, crank everything up and see how low the voltage gets.
 
topgone said:
All motors have utilization voltage stamped on their nameplates. That will be the voltage measured at the terminals of the motor. When the utilization voltage says "460V", that means it will be very happy running at -5%. NEMA even requires manufacturers to make induction motors that can work fine with a 10% voltage variation, and a 6% limit on universal motors.
Click to expand...
I agree with you on this, my voltage reading that I’m getting the 462 is st the motor control center I’m guessing on the contractor. It’s a digital read out… I haven’t measure actual voltage, but since it’s probably another 200ft away I’m guessing it’s going to be lower….

steve66 said:
462 volts where? At the service? At the motor?

If the voltage is lower due to feeders or branch circuits, that's not the utilities fault.

Here is one standard for utility service voltage tolerances, so it looks like you are well within that:

Voltage Tolerance Standard – ANSI C84.1 – Voltage Disturbance

voltage-disturbance.com

If you are really worried, crank everything up and see how low the voltage gets.
Click to expand...
The lower voltage readings is at the secondary of po co transformer, and at the digital read out motor center probably 30 ft from secondary…

so we had 472 at the 1st transformer it runs 150hp leg motor and a ton of other large loads. I had them take it up two taps and now it with the leg running the voltage is 488volts. This is from the digital read out in the motor control center. The other transformer is tapped all the way out and I get 467 bolts on secondary side with no load running… could it be that the poco primary run is longer to one transformer than the other cause of voltage drop
 
NEMA says:
The National Electrical Manufacturers Association (NEMA) standards recommend that motors should be designed to operate satisfactorily at a voltage variation of plus or minus 10 percent. For 230 volts, that range is 207 to 253 volts; for 460 volts, it is 414 to 506 volts.
Click to expand...
 
ctaylo360860 said:
I agree with you on this, my voltage reading that I’m getting the 462 is st the motor control center I’m guessing on the contractor. It’s a digital read out… I haven’t measure actual voltage, but since it’s probably another 200ft away I’m guessing it’s going to be lower….


The lower voltage readings is at the secondary of po co transformer, and at the digital read out motor center probably 30 ft from secondary…

so we had 472 at the 1st transformer it runs 150hp leg motor and a ton of other large loads. I had them take it up two taps and now it with the leg running the voltage is 488volts. This is from the digital read out in the motor control center. The other transformer is tapped all the way out and I get 467 bolts on secondary side with no load running… could it be that the poco primary run is longer to one transformer than the other cause of voltage drop
Click to expand...

For a 460V motor I wouldn’t panic just yet…
 
I didn’t think of that, but Not that I’m aware of. It’s mostly and industrial grain facility.
Lots of legs, augers, drags that type of thing…
There is a small building with ac on the property but I believe it’s fed from a separate transformer bank. Should be single phase 120/240 or possible 120/208!
 
ctaylo360860 said:
Would temperature be a factor as wel? I noticed today was cooler and the voltage seemed no to dip down near as much?
Click to expand...
Temperature definitely has something to so with it, but it’s on a primary/transmission level.
transmission lines have VD also on hot days with all the cooling loads throughout a system or circuit.
Ive seen 115kV transmission lines with +- 5000V
 
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