Thermo King KD-II SR, Manual

Page: 70 / 182

Electrical Maintenance (Rev. 04/03)
56
Troubleshooting the Phase Conversion System
If the electric motor does not run properly, first check the line voltage, the motor contactor, and the motor overload relay. if
these are all acceptable, test the electric motor to narrow down the possible causes for the problem. See the Troubleshooting
Chart for the individual component tests.
Electric Motor Tests
Test 1. Run the motor with three-phase power.
Disconnect the T1, T2, T2A, T3E, and T3F wires from the motor and connect three-phase power directly to the motor. Con-
nect L1 to leads 1 and 7, connect L2 to leads 2 and 8, and connect L3 to leads 3 and 9. Start and run the unit. Check and record
the voltage and current readings in the following chart.
The ideal voltage is 208 to 235 volts ac and the voltage should not vary more than 10% between the sets of wires. If the volt-
ages are out of these ranges, check the power source.
The start current should be approximately 75 amps.
The run current should not exceed 14.5 amps.
The current should not vary more than 10% between wires.
If the run current is higher than 14.5 amps in all three wires, check the suction pressure regulator setting before replacing the
motor. Check the setting of the suction pressure regulator by observing the suction pressure while the unit is running in defrost.
If the suction pressure is higher than 19 psig (131 kPa), the suction pressure regulator must be adjusted or replaced.
Replace the motor if currents are out of these ranges.
Test 2. Run the motor with single-phase power and the phase conversion system connected to the motor.
Remove the electrical connection box cover on the motor, and check and record the current readings in the following chart.
Wires Voltage Wire Start Current Run Current
L1-L2 L1
L2-L3 L2
L3-L1 L3
Wire (Motor Lead) Start Current Run Current
T1 (1)
T1 (7)
T2 (3)
T2A (9)
T3E (2)
T3F (8)