Figure 3-9.--Brush holder and brush-rigging assembly.

machine, use a throttling valve to reduce the

Keep machines

good

mechanical

pressure. Always blow out any accumulation of water

condition.

in the air lines before directing the airstream on the

part or ma-chine to be cleaned. Be certain that the

The following paragraphs will discuss some of the

compressed air does not have any grit, oil, or

procedures to follow when performing maintenance

moisture content in it. Compressed air should be used

and repair on motor generators.

with caution, particularly if abrasive particles

(carbon, and so on) are present, since these may be

Brushes

driven into the insulation or may be forced beneath

insulating tapes or other possible trouble spots. If

Brushes used in electric motors and generators are

vibration exists, check for loose parts or mounting

constructed of one or more plates of carbon, riding on a

bolts.

commutator, or collector ring (slip ring), to provide a

Motors, generators, and other electrical equipment

passage for electrical current to an internal or external

that have been wet with salt water should be flushed

circuit. The brushes are held in position by brush

out with fresh water and dried. Never let the

holders mounted on studs or brackets attached to the

equipment dry before flushing with fresh water. For

brush-mounting ring, or yoke. The brush holder studs,

complete information on washing and drying

or brackets, and brush-mounting ring comprise the

procedures, refer to NSTM, chapter 300.

brush rigging. The brush rigging is insulated from, but

The key points in the maintenance of electric

attached to, the frame or one end bell of the machine.

generators and motors are as follows:

Flexible leads (pigtails) are used to connect the brushes

to the terminals of the external circuit. An adjustable

Keep insulation clean and dry.

spring is generally provided to maintain proper pressure

of the brush on the commutator to effect good

Keep electrical connections tight

commutation.

Figure

3-9

shows

typical

77.70

Figure 3-9.--Brush holder and brush-rigging assembly.

3-17