TM 5-4320-274-14&P
Section III. GENERAL MAINTENANCE
5-5. Electric Motor Testing
WARNING
Do not attempt maintenance on the motor when electrical cable is connected to the power source.
a. Preparation. Disconnect the power cable shown in figure 4-1.
b. Testing.
(1) Using a suitable test lamp circuit, test for continuity between each of the motor phase wires. Replace the
motor if the lamp does not light. Test for grounds between one motor phase (any one) wire and the frame. If lamp is lit,
replace the motor.
(2) Use a megohmmeter and measure the insulation resistance of the stator assembly as instructed in TM 5-764
(Electric Motor and Generator Repair). The insulation resistance should not be less than 0.25 megohms.
(3) Connect the electric motor leads to a balanced voltage source of 3-phase, 60 hertz, 208 volt power. Operate
the motor under its normal load and measure the amperage in each motor lead with a hook-type ammeter. The
amperage in the three leads should be equal and not more than 6.3 amperes per lead. Measure the shaft speed with a
tachometer. The speed should not be less than 3450 rpm (revolutions per minute).
5-4