1VFD-5 motors

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ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Small industrial customer called with VFD that would not stay online. One of the 5 motors it controls had failed. During the "tell me" stage of the service call the customer noted that a couple months ago they had changed out 2 of the 5. The load side of the drive feeds a terminal block that has 5 manual motor starters tapped from it to each of the 5 motors. The two motors they installed ran backwards so they switched 2 of the leads from the drive to the terminal block, pretty obvious by the way the wires lay. Afterwards all 5 ran the correct direction. Is this possible or am I not quite hearing the whole story? Happens, very rarely and only to me I am sure.
 
ptonsparky said:
Small industrial customer called with VFD that would not stay online. One of the 5 motors it controls had failed. During the "tell me" stage of the service call the customer noted that a couple months ago they had changed out 2 of the 5. The load side of the drive feeds a terminal block that has 5 manual motor starters tapped from it to each of the 5 motors. The two motors they installed ran backwards so they switched 2 of the leads from the drive to the terminal block, pretty obvious by the way the wires lay. Afterwards all 5 ran the correct direction. Is this possible or am I not quite hearing the whole story? Happens, very rarely and only to me I am sure.
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No, if they switched the wires FROM the drive TO the distribution block, then ALL of the motors would have changed direction. But if they swapped 2 leads only on each of the motor circuits they changed out, then only THOSE motors would change direction. More likely they swapped leads from the terminal block to the manual motor starters, then forgot what they did.

VFDs are not magic, they are just a new power source.
 
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