GEK±91584D, Vertical Drilling Motor, Type GE752
ing caps. Thermometers should contact the bearing caps for best results.
2.Seat the brushes and run for ten minutes at 900 rpm.
Frame temperature should not exceed 25 C rise.
3.With machine running up to speed, measure vi- bration. Vibration should not exceed 0.002 on commutator end. If vibration exceeds this amount, rebalance the armature.
4.Check the commutator for roughness and make sure the brushes are riding properly.
5.Use a listening rod to check for noisy bearings.
6.Stop the machine and mount an indicator on the frame. While turning the armature by hand, mea- sure commutator runout. It should not exceed 0.001 in.
7.Measure field impedance. With 60 Hz a±c and 24 amperes through each field, measure the volt- age drop across total exciting and commutating fields. See the DATA section for voltage limits.
8.Apply a high±potential test to the windings of the assembled machine, as specified in the DATA section.
WARNING: Electric shock can cause serious or fatal injury. Proper precautions should be taken and observed by personnel performing testing to avoid such injury.
TESTING SHUNT MACHINES (Models 5GE752UP and US)
After the motor has been reconditioned and reas- sembled for service, make the following tests to be sure it will operate satisfactorily.
Connect the motor to a d±c welding generator. Refer to connection diagrams (Figs. 21 and 23) for connec-
*Product of Johns Manville Co.
tions. Run the machine by separately exciting the shunt field from a 125 vdc source. From another source of power, apply voltage to the armature circuit until the de- sired speed is obtained.
Motor Operation
Ventilated (2300 cfm at 7.6 in. H2O at Commutator Chamber)
Hold separate field excitation at 50.5 amperes. Vary the armature voltage to obtain the required rpm. At ap- proximately 700 terminal volts (no load), the speed will be 900 rpm.
Unventilated
Hold the separate field excitation at 10 to 15 am- peres. Vary the armature voltage to obtain the required rpm. At approximately 338 terminal volts (no load), the speed will be 900 rpm.
1.Run the motor for five minutes at 450 rpm. In- crease the speed to 900 rpm and run for two hours. Bearing temperatures should not exceed 70 C (158 F). Run until the bearing tempera- ture remains constant for 30 minutes. Increase the speed to 1300 rpm and hold it while perform- ing Steps 2, 3 and 4. Then shut down the motor. Do not exceed 1300 rpm.
2.Measure vibration when running the motor up to speed. Vibration should not exceed 0.004 in. If excessive, rebalance the armature.
3.Check the commutator for roughness. Be sure brushes are riding properly.
4.Listen for noisy bearings with a listening rod.
5.Stop the motor and mount an indicator on the frame. Turn the armature by hand and measure commutator runout. Runout should not exceed 0.001 in.
6.Measure the insulation resistance of the wind- ings with a megohmmeter. If the resistance mea- sures not less than one megohm, apply an a±c high±potential test to ground for one minute as outlined in the DATA section.
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