480v - 240v delta wired as step up transformer motor running in reverse

[Brad205]

I have a Primary 480 volt delta to Secondary 240 volt delta transformer that I rewired as a step up transformer using the instructions from the transformer. I am getting 484v on all 3 legs. The issue is when connected to the motor (40Hp) the motor is running in reverse. I have tried reversing the 3p wires in different combinations but this does not reverse the motor. What can cause this, any assistance is appreciated.

 

[ptonsparky]

Switch only two of the leads. Typically at the motor starter.

 

[Brad205]

I have done this at the motor switch and at the transformer and neither make a difference

 

[Brad205]

i can try to switch L1/L3 on the motor itself (kind of hard to get to) but this was running at the location i purchased it from just fine so i though it would be with my wiring (transformer or motor switch)

 

[augie47]

Rotation definitely should reverse if you swap any two leads in only 1 place. Does not matter which two or what place as long as you only swap in one place.

 

[hillbilly1]

Does this motor have a vfd? If so, change the leads on the load side only. If you change them on the line side, the vfd will always put out the same rotation, regardless of the input.

 

[Brad205]

i will give that a try and advise

 

[Jraef]

Does this motor have a vfd? If so, change the leads on the load side only. If you change them on the line side, the vfd will always put out the same rotation, regardless of the input.

Yep. VFDs don't give a rat's butt what the incoming rotation is, all it does is rectify the AC to DC, so rotation on the input side is totally irrelevant.

If you DO have a VFD, the incoming 480V needs to be Wye, not delta. You might get away with it for a while, but the VFD is not going to like it.

 

[hillbilly1]

Yep. VFDs don't give a rat's butt what the incoming rotation is, all it does is rectify the AC to DC, so rotation on the input side is totally irrelevant.

If you DO have a VFD, the incoming 480V needs to be Wye, not delta. You might get away with it for a while, but the VFD is not going to like it.

It used to be easy finding building rotation by bumping the indoor fan on a rtu, when connecting a temporary generator, and the utility is dead. Then they started putting vfd’s on them. Now you have to hope the cardboard baler or trash compactor doesn’t have one! I always mark the gear after I find out for the next guy. If it’s a blue or orange box, at least you can check it with the radial arm saw.