Page 3-24
Maintenance 3.18 - Electric Motor
MX15/19
3.18 E
LECTRIC
M
OTOR
T
ROUBLESHOOTING
1. Read the nameplate to become familiar with the motor, especially the rated voltage.
2. Try to turn the shaft by hand. Keep motor leads separated while doing this. If the shaft turns
freely, go to step 3. If the shaft won’t turn, proceed to step a.
a. The shaft could be tight for a number of reasons; this check is to determine if the tight-
ness is of a temporary nature only. Obtain power to produce the nameplate voltage. Do
not make a permanent connection. First, touch the motor leads quickly to the power
supply just long enough to observe if the shaft runs. If it does turn, then hold the motor
leads on the power supply for a longer time. If the motor sounds normal, go to step 3. If
the motor sounds noisy, it should be taken apart as described in the disassembly sec-
tion.
3. If the motor turned freely, connect an ammeter in the circuit, as shown in Figure 3-25A. With
rated voltage applied and the shaft running free, the ammeter should read less than 20% of
the nameplate full load current. If the motor meets the above conditions, then it can be
assumed the original problem is external to the motor.
D
ISASSEMBLY
1. Remove thru bolts.
2. Remove pulley end cover.
3. Pull the armature out of the assembly in one swift motion.
4. Remove commutator end cover.
NOTE: Do not place the stator ring in any mechanical holding device during the disassembly or assembly
operation. Permanent distortion or other damage will result.
I
NSPECTION
Once the motor has been disassembled, go through the following check list steps to determine
where the problem lies.
1. Bearings should spin smoothly and easily, have ample lubrication, and be free of corrosion.
2. Armature should be checked for grounds and shorted turns. Refinish commutator surface if
pitted or excessively worn.
3. Brushes should be checked for wear and to ensure that they are free in the brush holders.
NOTE: Observe how brushes are assembled in brush holders and position of brush lead. New brushes
must be installed in same manner. Brushes should be removed as follows:
a. Remove brush spring clip from its mounting on brush assembly.
b. Lift brush assembly from brush holder.
c. Disconnect brush assembly lead.
d. The new brush assembly isto be installed by reversing Electric Motorabove procedure.
4. Inspect wire harness and all connections for signs of damage due to overheating.
5. Check stator to see that it is securely mounted.
R
EASSEMBLY
1. Install new brushes and be sure that they are free in the holder. Install brush with the lead
wires positioned as when received. Raise all brushes to the locked position. (See Figure 3-
17B and step 3 in the Inspection section above.)
2. Place commutator cover on a work bench with brush assembly facing upward.
3. Place the bearing spring into the bearing bore.
4. Take a complete armature assembly, including bearings, and insert commutator end bearing
into the bearing bore.
NOTE: Do not reuse bearings which have been removed from armature shaft. Keep assembly in a vertical
position. Use extreme care not to damage armature with bearing pullers. New bearings should be
installed by pressing inner race of bearing onto proper position on armature shaft.
5. Set the brushes to final position as shown in Figure B.
6. Place the complete stator down over the vertical armature and into position on the commuta-
To Next Page
Loading...
Need help?
General
