480v high leg motor issue

[journeyman0217]

i am troubleshooting a three phase 480 motor with voltage issues that is fed by a high leg system. I dont have to much experience with this set up. Would the configuration of the connections to the motor matter? It is fed by a 3 wire 480v delta high leg system. i did not think it would matter because it is a 3 phase motor, not single phase.

 

[augie47]

What type of "voltage issues"?

 

[journeyman0217]

There is a "low voltage" relay that shuts the motor down

 

[curt swartz]

Are you sure this a Delta system with a high leg and not a corner grounded delta?

 

[winnie]

The motor should only care about L-L voltage, but perhaps the relay cares about L-G voltage

 

[ptonsparky]

Picture of that relay?

There is a "low voltage" relay that shuts the motor down

 

[ptonsparky]

Has it been working or is this a new installation?

 

[hillbilly1]

There is a "low voltage" relay that shuts the motor down

Usually those also have phase loss protection too. It would be unusual for a 480 volt service to have a high leg, unless it was corner grounded. I’m betting a blown fuse.

 

[ptonsparky]

Usually those also have phase loss protection too. It would be unusual for a 480 volt service to have a high leg, unless it was corner grounded. I’m betting a blown fuse.

Yes, to the Phase Loss protection.

?? to High leg and corner grounded.

Blown fuse a good possibility.

 

[journeyman0217]

It’s a step up transformer. Service coming in is 240v three phase high leg. Steps it up to feed the motor.

 

[ptonsparky]

It’s a step up transformer. Service coming in is 240v three phase high leg. Steps it up to feed the motor.

Hi leg primary does not mean you have hi leg secondary.

 

[ptonsparky]

Is this a new installation?
Is this transformer designed for reverse feed of step up?
It appears to be step down.

 

[journeyman0217]

Hi leg primary does not mean you have hi leg secondary.

I'm trying to understand it...wouldn't the secondary induced voltage have the same effect as the primary? Wouldnt my voltage on the 480 side be (L1-G 240, L2-G 416, L3-G240)?

 

[journeyman0217]

Is this a new installation?
Is this transformer designed for reverse feed of step up?
It appears to be step down.

It is not a new installation

 

[retirede]

I'm trying to understand it...wouldn't the secondary induced voltage have the same effect as the primary? Wouldnt my voltage on the 480 side be (L1-G 240, L2-G 416, L3-G240)?

Only if the center of the L1-L3 winding was bonded to “ground.” Does the winding even have a center tap?

 

[ptonsparky]

OP, That is a Delta to Delta transformer. You would need to bond the secondary at some point to get a reliable reference voltage to ground.
I don't think that transformer is being used correctly if it is step-up as you suggest. It may not have anything to do with your problem though.

Only if the center of the L1-L3 winding was bonded to “ground.” Does the winding even have a center tap?

No center tap.

 

[journeyman0217]

Only if the center of the L1-L3 winding was bonded to “ground.” Does the winding even have a center tap?

I dont believe it does. So if no winding is bonded to ground, in theory what should my voltages be to ground on the 480 side?

 

[journeyman0217]

I know its not referencing a center tap, but what is the dotted line coming off of H1 and X1 referencing?

 

[kwired]

Only if the center of the L1-L3 winding was bonded to “ground.” Does the winding even have a center tap?

It is a delta-delta transformer and has no center tap according to posted nameplate. there are voltage adjustment taps on the high voltage side. If OP is having low voltage issues the tap being used could possibly come into play. Being reverse fed situation he probably should use one of the mid range taps though.

 

[kwired]

I know its not referencing a center tap, but what is the dotted line coming off of H1 and X1 referencing?

Phase rotation reference between primary and secondary?