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.
480v - 240v delta wired as step up transformer motor running in reverse
- Thread starter Brad205
- Start date
ptonsparky
Tom
- Occupation
- EC - retired
Switch only two of the leads. Typically at the motor starter.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
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.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
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
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
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.