High Power Dc Motor 4

[Hesab]

Hi
In our factory we are using high torque reversing dc motor.the specification of this motor is : Westinghouse Electric - 1250 Hp - 40/120 RPM 700 Vdc - 1540 Amp . Recently because of some malfunctions we've replace the rotor and mount spare one ( 22 ton !! ) after that we start the motor and realize that in Forward direction the brushes have sparks in some holders and in reverse direction it has not any sparks but operator said that the amps is higher than forward .
What's the reason and how can we achieve best performance of machine ?

 

[Hesab]

At first thanks for your advices.
We find the correct neutral position of brushes and adjust it.
and now the amp of CCW and CW of rotation are almost equal.
at the nameplate amp the brushes haven't any sparks . but when the motor operates at the 200% overload we can see little sparks under some brushes .

dArsonval: three month ago we realize that commutator make some noise(chatter ) when the armature rotate at high speeds(about 40 to 50 rpm ) . it was clear that the frequency of noise is proportional to commutator speed . so we call some repair shops to prevent more damages . after investigations they said to us one region of commutator segments needs to repair and the segments becomes up!! . they said that the commutator only needs to grinding . but we think that we must choose another services ( or tests ) to make sure that segments are in good condition .

is it realy enough only grinding the commutator ?

 

[Skogsgurra]

Thanks for the feedback! Good to hear that old routines still work.

Sparking at 200 % load is not unusual. Some motors spark at 150 %. So you did a good job with the brush position.

The reason that segments rise above the others is usually that there has been a high current flowing for some time. If you measure the difference (use an indicator clock) and find that the difference is more than 100 microns (0.1 mm), then you probably need to use a lathe to correct the difference. But if less than that, grinding in the motor is adequate.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[electricpete]

Good call Gunnar.

=====================================
(2B)+(2B)' ?

 

[starkopete]

We rebuild rougher motors (old Fairbanks Morse navy propulsion motors) for a Mill that has similar problems. We would set the neutral in the shop as suggested above but the customer would still get what they considered excessive sparking at over 150% load. Because of the construction of these motors (the brush rigging rides tightly in a machined groove) we were able to fabricate a type of micro-adjuster on the rigging so that the customer could “tune” it while in place. They adjust the rigging one way or the other until they get minimal sparking when the motor is (over)loaded. (Of course they adjust the rigging with the motor off).

Thanks

 

[Hesab]

Skogsgurra
1: why the segments rise and how we can avoid this condition in future?

2:how can we be sure that the segments are in good condition?
is there any posibility that some of them cracked?

 

[edison123]

Hesab

When the commutator diameter is worn out, then the segments can rise up due to centrifugal forces. Another reason could be that the motor went into sustained overspeed.



Muthu

http://www.edison.co.in