GE GE752 Glass Band, Commutator End, Wire Band, Drive End, Resurfacing, Tightening, Motor Frame

GEK±91584D, Vertical Drilling Motor, Type GE752

tion. A reading of one megohm or higher should be obtained. If necessary, perform additional cleaning and baking operations to obtain this val- ue before proceeding.

NOTE: If additional cleaning and baking opera- tions do not increase the resistance value of the insulation, it may be necessary to replace the creepage band and rewind the armature.

2.Measure and record armature resistance. See the DATA section for values.

3.If there are no armature coils grounded, perform

abar±to±bar comparison test to check for open or short±circuited armature coils.

a.Pass a regulated d±c current through the ar- mature coils.

b.Read the voltage drop between the commu- tator segments with a millivoltmeter. If the reading varies more than plus or minus 5%, a defective or short±circuited coil is indicated. If the armature fails the bar±to±bar test, the ar- mature must be rewound.

If the armature will not be rewound, proceed to inspect the following items.

Insulation

Inspect the insulation of armature coils for cracks, physical damage, burns and deterioration. If minor re- pairs are required, refer to Fig. 19 for insulation details.

Glass Band, Commutator End

Inspect the glass bands for split, frayed or loose con- dition.

Wire Band, Drive End

check for movement of the band to determine if loose. If the band is loose or has deep burns, replace it. See RE- PAIR section for instructions.

COMMUTATOR

Check the commutator for threading, pitting, groov- ing, burns, flat spots, high bars and copper drag.

Check the commutator to make sure that it is not out±of±round. See the DATA section for concentricity limits.

Resurfacing

For the resurfacing procedure for a commutator, see REPAIR, Armature section.

Refer to the DATA section for the minimum permissi- ble commutator diameter dimension and check the di- ameter of the commutator.

NOTE: If the brush surface diameter will be less than the minimum permissible diameter after resurfacing operations are performed, the com- mutator must be replaced.

Tightening

If the commutator is loose (has high bars), see the ªREPAIR, Commutator Tighteningº section for instruc- tions to tighten the commutator.

ARMATURE SHAFT INSPECTION

Armature shaft bearing fit dimensions can be checked and compared to armature shaft drawings pro- vided in Fig. 20. If the bearing fit dimensions are not within stated tolerances the shaft must be replaced or repaired. Refer to Table 2 to determine the correct shaft drawing for the machine being repaired.

MOTOR FRAME

Inspect the wire band for physical damage, loose tie clips or broken wire.

Creepage Band

Inspect the surface of the Teflon creepage band for possible flashover damage. Tap the band lightly and

1.Check the connection strap insulation for dam- age, signs or burning, cracks or discoloration.

2.Check the insulation on the coils for damage, signs of burning, cracks or discoloration.

3.Check the lead cables for damage, overheating and signs of deterioration.

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