DC Motor heavy sparking

[Leendabests]

Dear friends,

Currently i am facing a problem With DC Motor.problem is mentioned below:

1. DC motor was overhauled.Rewound Field Interpole and armature windings.all windings are in good condition with 2000 Mohms value.
2.Polished and skimmed the commutator,,drop tested. found ok.
3.Brush and carbon holder is in good condition.

Now the problem is motor is giving heavy sparking on load. Application of motor is boom hoist motor.

On No load motors runs smooth no sparking,no vibration.

Why it's giving heavy spark on load and we opened twice the motor but not able to get the root cause.

Anything else that i need to check?

 

[Skogsgurra]

Brush position checked? Use AC on main field and adjust bridge for minimum voltage.

If really heavy sparking; not unusual that today's winder shops connect interpoles with wrong polarity. Have seen that twice very recently.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[Leendabests]

Brush position checked and adjusted. No sparking free load. When motor getting full load, the commutator sparking and motor tripped. It is related to drive problem?

 

[Skogsgurra]

Yes, could be excessive ripple. If you hear a nice 300 (or 360 in 60 Hz land) Hz "singing" then the drive is probably OK.
If there is a distinct "growl" - it is probably the drive. Have you checked the gating pulses for symmetry?

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

When the shop trimmed the commutator did they also clean up the rotor body? An increased air gap will cause problems.

Bill
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"Why not the best?"
Jimmy Carter

 

[mikekilroy]

How do you know interpole windings were not reversed? We too have seen this happen from low cost motor repair shops.

What causes motor brush sparking under load and not under no load? You need to get a handle on this before going forward. I would venture sparking loaded and not unloaded means you are putting more V*A (POWER) thru brushes than they were designed for (assuming the motor is not defective due to winding issues or brush location issues). There is a max they can transfer, the higher the power transferred, the higher the sparking. Maybe time to get back to the basics of it all to help identify where to look?

1) but what is motor amps rating?
2) what are you pulling?
3) If exceeding rated armature amps, time to verify field volt is proper for the speed you are running when sparking? If not, then the motor will pull way more amps and spark too....

Why did you send motor out to begin with?
Same sparking reason? Other?

does output shaft rotate easy with motor off? Ie., do you have a mechanical problem causing hi current (torque) draw?

You really need to rule out these questions before jumping into blaming the motor or drive....

http://www.KilroyWasHere<dot>com

 

[rhatcher]

It sounds like the armature and interpole polarities are incorrect relative to each other. This can happen several ways.
- armature wound retrogressive instead of progressive (or visa versa)
- interpoles wound with wrong polarity
- interpole circuit reversed
- armature circuit reversed

Under these conditions there will be no sparking when operated at no load because the current through the armature and interpoles is too low to have any effect. Under load, the incorrect polarities will cause the interpoles to boost the armature reaction instead of bucking it, therefore shifting the armature neutral away from the brush position.