GE VERTICAL DRILLING MOTOR GE752 - Manual (Page 56)

GEK–91584D, Vertical Drilling Motor, Type GE752
56
Minimum Volts 7.3 . . . . . . . . . . . . . . . . . . . . . . .
Maximum Volts 8.5 . . . . . . . . . . . . . . . . . . . . . . .
For Magnetic retainers:
Minimum Volts 0.7 . . . . . . . . . . . . . . . . . . . . . . .
Maximum Volts 12.4 . . . . . . . . . . . . . . . . . . . . . .
High–Potential Test
Frame With Used Coils
Apply a high–potential test voltage of 2000 volts, 60
Hz for one minute.
Frame With All New Coils
Apply a high–potential test voltage of 3500 volts, 60
Hz for one minute.
Measure leakage current to ground during this test.
5.0 milliamps is maximum.
WARNING: Electric shock can cause serious
or fatal injury. To avoid such injury, personnel
should take and observe proper precautions
during the high–potential testing.
Resistance Measurement
Refer to the DATA section for values and measure
the resistance of the exciting and commutating fields.
VARNISH TREATMENT (ARMATURE)
Vacuum Pressure Impregnation (VPI)
After all repairs have been completed, the armature
must be vacuum pressure impregnated in GE–702C
polyester varnish.
Refer to GEK–101183 for VPI procedure.
Following the VPI processing, the armature must be
given a varnish immersion treatment.
NOTE: Do NOT clean previously protected ma-
chined surfaces, threads and tapped holes be-
fore varnish treating the armature.
Varnish Immersion Treatment After VPI
(Armature)
The following immersion process must be performed
on the armature assembly after the VPI process.
1. Preheat the armature in an oven at 140
_
C for at
least five hours.
2. The temperature of the armature must not be
less than 90
_ C, or above 120 _ C, before im-
mersing. Immerse the armature in a vertical po-
sition (commutator end up) in the varnish (GE
Spec. No. A15B53A) for at least one minute.
NOTE: One minute is the minimum time to in-
sure adequate varnish penetration.
3. Lift the armature out of the varnish and spin until
the excess varnish is removed. Clean the shaft
with Xylene (GE Spec. No. D5B9).
4. Bake at 140
_
C in an oven for at least eight
hours.
BALANCING ARMATURE
Refer to the appropriate longitudinal section (see
Table 2, Page 20, to determine the correct drawing) for
balance weight locations. Dynamically balance the ar-
mature within 10 grams (0.35 oz.) on the drive end and
12 grams (0.42 oz.) on the commutator end by adding
weights on the commutator cap and the armature head.
REASSEMBLY
Brushholders
1. Using a bolt and washer, attach the brushholder
clamp to the frame mount. Position the studs of
the brushholder in the clamp, and move the
brushholder radially outward as far as possible.
2. Tighten the brushholder clamp bolt but do not
torque. Install all brushholders.
3. Connect the brushholder cables. Refer to Table
2, Page 20, to determine the correct connection
diagram.