480 volt motor

Status
Not open for further replies.
Hello all. I have a problem with a three phase 480 volt electric motor that I unhooked to have repaired. It has two contactors, one starts than the second one starts once the motors up to speed. It had six motor leads I numbered all my feed lines so I could install it after repair. So I did just that and now the motor spins in the wrong direction. I could only find info about a star delta connection but my setup only has two contactors not three. My concern is if I swap two legs and get the motor spinning right and the second winding kicks in how do I know if it's phased right. Could I start either winding individually and see rotation. Any help would be greatly appreciated.
 

LEO2854

Esteemed Member
Location
Ma
Hello all. I have a problem with a three phase 480 volt electric motor that I unhooked to have repaired. It has two contactors, one starts than the second one starts once the motors up to speed. It had six motor leads I numbered all my feed lines so I could install it after repair. So I did just that and now the motor spins in the wrong direction. I could only find info about a star delta connection but my setup only has two contactors not three. My concern is if I swap two legs and get the motor spinning right and the second winding kicks in how do I know if it's phased right. Could I start either winding individually and see rotation. Any help would be greatly appreciated.
If it is running in the right direction, then it is phased right.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
If it is running in the right direction, then it is phased right.
And if he reverses one winding (including the wires to both contactors) and it starts up then goes bonk when the second contactor pulls in? Reverse the leads to that contactor only?
Is there a less risky way to check, is what the OP is asking, I think.
In theory, the rotation should not have changed if he properly marked both sets of feeder connections. Therefore the theory does not apply for some reason. :)
 
The motor is spinning in the wrong direction. Im concerned that both windings won't be in phase with each other. This is a big motor I don't recall the hp. The amperage is 86 amps at 480. Each winding is 43 amps. I can't take a risk of motor damage. I was sure to mark every lead could the rebuilder changed something when it was rebuild?
 

electric_cal

Member
Location
California
Hello all. I have a problem with a three phase 480 volt electric motor that I unhooked to have repaired. It has two contactors, one starts than the second one starts once the motors up to speed. It had six motor leads I numbered all my feed lines so I could install it after repair. So I did just that and now the motor spins in the wrong direction. I could only find info about a star delta connection but my setup only has two contactors not three. My concern is if I swap two legs and get the motor spinning right and the second winding kicks in how do I know if it's phased right. Could I start either winding individually and see rotation. Any help would be greatly appreciated.

It appears that the motor shop connected the motor T-Leads in a different configuration inside the motor. Just like any 3 phase motor, if you change any 2 of the motor feeders it will then run in the other direction. You just need to make sure that the leads that you change on the start contactor and the run contactor are the same. You can then verify the motor rotation by engaging the start contactor only first and verify correct rotation. Then engage the run contactor and verify correct rotation. If both rotate correctly, then you are good to go.
 
Thank you everyone. I have never seen anything like the starting system these motors have but one thing I knew I could find a answer here. Thank you electric-cal.
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
Have you considered swapping the two phases between the contactors and the breaker feeding them? The line side?
 

jimdavis

Senior Member
FYI the type of motor you describe is called a part winding start motor. A typical part winding motor is arranged so that one half of it's primary winding is energized initially, the remaining half then energized after a time duration. Both halves then carry equal current. It's a fairly common configuration for medium-sized motors.
 

kwired

Electron manager
Location
NE Nebraska
FYI the type of motor you describe is called a part winding start motor. A typical part winding motor is arranged so that one half of it's primary winding is energized initially, the remaining half then energized after a time duration. Both halves then carry equal current. It's a fairly common configuration for medium-sized motors.
Usually the delay is pretty short, and from OP description should have normally closed the second contactor during the time he ran it. This starting method is to reduce the "inrush" starting current by energizing only half the windings at a time. The delay is normally only a few seconds at the most. Usually only half the windings will not be able to accelerate the load fast enough if the second half is not energized fairly soon after the first half.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Have you considered swapping the two phases between the contactors and the breaker feeding them? The line side?
Add my vote for this too...

That way no matter WHAT type* of motor it is, the phasing will follow through.

*Could be PW, but could also be 2S2W, or even Wye-Delta that is only using two contactors, we have no idea.
 

xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
Hello all. I have a problem with a three phase 480 volt electric motor that I unhooked to have repaired. It has two contactors, one starts than the second one starts once the motors up to speed. It had six motor leads I numbered all my feed lines so I could install it after repair. So I did just that and now the motor spins in the wrong direction. I could only find info about a star delta connection but my setup only has two contactors not three. My concern is if I swap two legs and get the motor spinning right and the second winding kicks in how do I know if it's phased right. Could I start either winding individually and see rotation. Any help would be greatly appreciated.

I would use the proper test equipment. If you don't have it phase right, there could be undesirable consequences..
 

meternerd

Senior Member
Location
Athol, ID
Occupation
retired water & electric utility electrician, meter/relay tech
Yup...likely a part winding start. Easy to hook up. Both starters have the line side connected to the same breaker. Most times, they wire to the first starter then jumper over to the second. As long as the phases are the same on the top side of the starter, they will be the same on the load side. To test rotation without a meter, just disconnect the motor leads from one or the other starter and give it a quick bump. Then do the same on the second starter. A quick bump on a part winding is not a problem. Just see that they both rotate in the desired direction. Motor leads are usually labeled with the first winding 1, 2, 3. Second may be 4, 5, 6 or 7, 8, 9. If in doubt about windings, do a continuity check between wires. Winding one will read low ohms between leads. Winding two will read the same. Winding one will not read to winding two. They're separate. If you have some other motor such as multi-voltage or star/delta, they are different. Be careful.

We have many pump stations with three of four pumps. One pet peeve of mine is finding someone reversing rotation at the starter. In my opinion, that's a headache. Phase sequence should be clockwise at the starter ABC, Brown Orange Yellow, left to right or top to bottom. Then, if you want reverse rotation at the motor, reverse the leads at the motor, not at the starter. Write the colors BOY or BYO inside the cover, so you'll always know. That way, any time you disconnect motor leads, you'll always know that it's Brown, Orange, Yellow Left to right. That's my opinion. If yours is different I'll loudly explain why you're wrong.;)
 
Last edited:
So I checked the rotation on both windings as electric-cal stated and they both where the same. So I decided to swap the two legs in the disconnect rather than in the control panel. So that's all set the motor started fine and ran fine. This motor is part of a pump that drafts out of a pond and feeds a hydrant system for a turf farm. Something happened that scared the living shit out of me as the pump was shut down, water hammer. The hole platform, motor and pump and piping system jumped violently as the pump stopped. I have no idea why it never happened before it was rewound. We had a hydrant open and a new check valve was installed. As long as it's not electrical it's not my problem.
 

meternerd

Senior Member
Location
Athol, ID
Occupation
retired water & electric utility electrician, meter/relay tech
So I checked the rotation on both windings as electric-cal stated and they both where the same. So I decided to swap the two legs in the disconnect rather than in the control panel. So that's all set the motor started fine and ran fine. This motor is part of a pump that drafts out of a pond and feeds a hydrant system for a turf farm. Something happened that scared the living shit out of me as the pump was shut down, water hammer. The hole platform, motor and pump and piping system jumped violently as the pump stopped. I have no idea why it never happened before it was rewound. We had a hydrant open and a new check valve was installed. As long as it's not electrical it's not my problem.

DANG! Go back and do it right!:rant: You'll thank me later.:happyno:
 
Last edited:
DANG! Go back and do it right!:rant: You'll thank me later.:happyno:

What would be wrong with swapping them in the disconnect. None of the ungrounded conductors are identified color wise. I figured it would be the better option because after each contactor every connection is numbered. The second winding starts two seconds after start
 
Status
Not open for further replies.
Top