9. BATTERY CHARGING EQUIPMENT
9.1 MOTOR-GENERATOR SETS
9.1 MOTOR-GENERATOR SETS
Diverter-pole motor-generator sets used for battery charging, , if properly
installed and maintained, will give long and satisfactory service. Shunt
generators with voltage regulating equipment are used as battery chargers in
some older installations.
Operation of the diverter-pole generator is similar to that of a shunt-wound
generator, except the field rheostat is set to maintain floating voltage. The
diverter-pole generator will maintain voltage within close limits and will
automatically adapt to fixed or fluctuating loads within its capacity and will
charge the battery at the proper rate.
Common problems with motor-generator sets involve the commutation
system, and frequent checking of commutators is desirable. After several
months of operation, a commutator should develop a smooth, burnished
surface, free from grooves, burns, or pit marks, and should be kept in this
condition. Never use oil or any other lubricant on the commutator.
Once each month, remove brushes from the holders and wipe off the
commutator, brushes, and brush holders with a clean, dry cloth. If oil or
grease are found on these parts, clean thoroughly with a cloth dripped in an
approved solvent. Follow with a cloth saturated with hydrogen peroxide and
thoroughly wipe dry with a clean cloth. The lower brushes have a natural
tendency to collect dirt and must be cleaned each month. If grooves
develop in the commutator, brushes should be lifted from holders, and the
faces of the brushes should be carefully inspected for embedded specks of
copper. These particles of copper or other hard spots should be carefully
removed with a knife point.
The grooves between commutator bars should be cleaned regularly.
Remove copper or carbon dust or other foreign matter. A thin, flat piece of
wood or fiber is recommended for this purpose.
Mica should always be located about 1/32 inch below the surface of the
commutator bars. When undercutting the mica becomes necessary, a knife
or broken hacksaw blade on which the "set" of the teeth has been ground off
is effective in scraping the mica to the required depth. Do not undercut the
mica more than 1/32 inch. Be sure that slots are left clean and that no
small flakes of mica project above the surface of the commutator,
particularly on the sides of the bars.
All sharp corners on the edges of the commutator bars should be rounded
off to prevent cutting or scraping the brushes.