DC Motor Trouble
DC Motor Trouble
(OP)
We are working on a Westinghouse motor.
Frame 620-MCA Volts 230 DC
rise 75 Deg C Series Wound
HP 275 RPM 370 Amps 975 Hrs 1
HP 360 RPM 340 Amps 1280 Hrs 5
Looking at the com side of the motor it will run ccw and draws 150 amps
the motor will turn in the cw direction. The motor draws 500 amps.
When the power is turned off it appears that the armature turns ccw about the distance of one bar segment of the comm.
We tried switching A1 and A2 from the test panel. The motor will still only turn ccw. With A1 and A2 in the correct spot, we changed S1 and S2. The motor will now turn in the cw rotation, but not ccw.
We tried connecting the A1 and A2 test panel leads directly to the brush holders and the motor will still only rotate ccw.
We did do a polarity test of the frame. The series fields are correct. The inter poles are also correct. All the brushes are properly seated to the comm.
Any thoughts?
Frame 620-MCA Volts 230 DC
rise 75 Deg C Series Wound
HP 275 RPM 370 Amps 975 Hrs 1
HP 360 RPM 340 Amps 1280 Hrs 5
Looking at the com side of the motor it will run ccw and draws 150 amps
the motor will turn in the cw direction. The motor draws 500 amps.
When the power is turned off it appears that the armature turns ccw about the distance of one bar segment of the comm.
We tried switching A1 and A2 from the test panel. The motor will still only turn ccw. With A1 and A2 in the correct spot, we changed S1 and S2. The motor will now turn in the cw rotation, but not ccw.
We tried connecting the A1 and A2 test panel leads directly to the brush holders and the motor will still only rotate ccw.
We did do a polarity test of the frame. The series fields are correct. The inter poles are also correct. All the brushes are properly seated to the comm.
Any thoughts?





RE: DC Motor Trouble
In your second sentence, what are you doing to turn it in cw direction when it draws 500A?
RE: DC Motor Trouble
Bill
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"Why not the best?"
Jimmy Carter
RE: DC Motor Trouble
All of the connections inside the motor look to clean and well connected.
RE: DC Motor Trouble
To get reversal, you have to break the series connection between the S and A leads, bring them both out to the outside, and then reverse only one, either the two S leads or the two A leads.
If that doesn't result in reversal of rotation, then something very strange is going on. The first thing I would be absolutely sure of is that this is really a series wound motor. Because of the difference in forward and reverse amps, I half suspect you have either a comp shunt or stab shunt motor. Both of them will have S and A leads but also F1 and F2 leads.
Let us know.
RE: DC Motor Trouble
Shunt motors can be easily reversed by the controller. Series can not and neither can some compound motors.(combination of series and shunt)
Your information says series.
Best regards,
Mark.
Mark Empson
L M Photonics Ltd
RE: DC Motor Trouble
The strange part of this is that the motor will turn no problem in the ccw direction but won't turn cw. That is said with A1 positive A2 negative S1 positive S2 negative. Change the drum switch to A1 negative A2 positive S1 positive S2 negative the motor hums and draws 500 amps and does not turn.
We tried turning the motor with no power to get it moving and turn on the power and it stops the armature.
I have seen something similar to this and we had a problem with the span of equalizer trays being 1-117 when it should have been 1-118. This was on a compound motor.
I was thinking we have a problem with the armature, but I was told this motor was in service and was taken out of service because the brake wheel was cracked. So we are at a loss of what is wrong.
RE: DC Motor Trouble
Also see h
Does it match that?
In reverse it will be (+)A2----A1->S1---S2(-).
RE: DC Motor Trouble
I have run other series motors without any troubles of reversing direction with the test panel we are using. This motor is should be easy to test run but doesn't make any sense.
RE: DC Motor Trouble
That is you may be interchanging A1 and S1 instead of A1 and A2. You can end up with full voltage across the armature and the series field shorted end to end, or vise versa.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: DC Motor Trouble
With the motor apart I did trace the leads and did not see any thing stand out to be out of place.
RE: DC Motor Trouble
You said the motor is reversing (cw rotation) when S1 and S2 are interchanged. What does it draw then?
Is the issue only when interchanging A1 and A2?
If it works with no issues with S1/S2 interchanged, the motor should be OK. May be something gets messed up (interpole winding?) while reversing A1 A2.
RE: DC Motor Trouble
RE: DC Motor Trouble
or test the motor without the "switch" or any of your test set up in both directions. If it works fine, then fix the switch!
RE: DC Motor Trouble
I don't think the test panel is the problem, or the drum switch for that matter.
Thanks for the help I will try a few of these suggestions on Monday.
I will post what we find out to let you all know.
RE: DC Motor Trouble
Make sure that the leads from the motor to the controller have the same numbers on each end.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: DC Motor Trouble
And this being a series field motor, it should not be run without a load to avoid run-away speeds. Do you any have load on the motor ?
RE: DC Motor Trouble
RE: DC Motor Trouble
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If we learn from our mistakes I'm getting a great education!
RE: DC Motor Trouble
RE: DC Motor Trouble