Voltage difference

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anbm

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Designer
Two same size motors are located in same room, power from same electrical panel but each motor receives a difference voltage,
what could be the issue?
 
Is this voltage difference under load or with the motors off?
and what are the voltages you are seeing
 
Hv&Lv said:
Is this voltage difference under load or with the motors off?
and what are the voltages you are seeing
Click to expand...
When both motors run, 480/3 is system voltage, the client mentions the voltage difference around 15-17V.
 
Voltage imbalance is a big deal to a motor.


Measure and record the voltage on each power lead. (L 1, L 2, L 3 )
Change all three power leads as follows: L 1 to L 2, L 2 to L 3, L 3 to L 1.
Measure and record voltage on each lead again. (L 1, L 2, L 3 )
If the imbalanced leg follows the motor lead, then a problem exists somewhere within the pump cable, connections, or stator winding.
If the imbalanced leg stays on the same control box terminal and jumps to a different motor lead number, then the problem is with the supply or control box.
 
anbm said:
When both motors run, 480/3 is system voltage, the client mentions the voltage difference around 15-17V.
Click to expand...
The way that is worded, it could mean that the two motor are different FROM EACH OTHER by 15-17V, or that the voltage AT BOTH MOTORS is 15-17V lower than the 480V line. Those are two totally different issues.

If it is the first thing, different from each other, 3.5% delta could easily be explained by the things that HV&LV mentioned.

If it's the second issue and they are just complaining that the motor terminal voltage is 15-17V lower than 480V when the motors are running, that's just someone not knowing how things work...
 
Jraef said:
The way that is worded, it could mean that the two motor are different FROM EACH OTHER by 15-17V, or that the voltage AT BOTH MOTORS is 15-17V lower than the 480V line. Those are two totally different issues.

If it is the first thing, different from each other, 3.5% delta could easily be explained by the things that HV&LV mentioned.

If it's the second issue and they are just complaining that the motor terminal voltage is 15-17V lower than 480V when the motors are running, that's just someone not knowing how things work...
Click to expand...
15V-17V voltage drop, i.e. 460V-463V was recorded at one motor but not the other motor. Sorry for the confusion...
 
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