MIL-DTL-17060G(SH)
d. With the motor running at rated input voltage and frequency and the axis of the shaft in its normal position,
the amplitude of vibration of the bearing housing in the direction giving the maximum amplitude shall be measured
and recorded. The motor shall be balanced with one-half standard key in keyway (that is, a key of full length flush
with the top of the keyway, where applicable).
4.6.7 End play.
4.6.7.1 Sleeve bearing motors. The end play of horizontal sleeve bearing motors shall be measured while at
standstill by alternately pressing and releasing the rotor shaft at each end.
4.6.7.2 Ball bearing motors. The end play of ball bearing motors shall be determined by clamping an indicator
to the motor frame and measuring axial shaft movement while applying an axial force to the shaft. The force shall
not exceed 150 percent of the weight of the rotor assembly. The shaft shall be moved through its free travel and
readings shall be taken. For heavy rotors, the motor may be lowered onto its shaft in a vertical position and the
weight of the motor released slowly onto the shaft and displacement measured. Enough weight shall be released to
support the motor without distorting the end shields. The process shall be repeated to confirm measurements.
4.6.8 Effectiveness of enclosure. Enclosed motors shall be tested in accordance with MIL-E-2036 and
MIL-STD-108 except that the drip test for a dripproof protected enclosure is not required.
4.6.9 Weight. The weight of motor and rotor shall be measured and shall conform to 3.6.4.
4.6.10 No-load input (induction motors only). Measurements of line volts and amperes, watt inputs, and
rotational speed shall be taken. The motor shall be run for a minimum of 1 hour to allow bearing losses to become
constant before any readings are taken. Where the rotor of the motor is supported by the bearings of the driven
auxiliary, this test may be conducted with the motor driving the auxiliary with the auxiliary unloaded.
4.6.11 Pull-up, breakdown, and locked-rotor torque and current (induction motors).
4.6.11.1 Test with motor operating at rated voltage. For motors rated at 60 hp or less, pull-up and breakdown
torque and locked-rotor current and torque shall be measured with the motor operating at rated voltage. For motors
rated in excess of 60 hp, testing should be performed at rated voltage with the exception that locked-rotor torque and
current may be measured with the motor operating at less than rated voltage as specified in 4.6.11.2 if testing at
rated voltage would exceed the kilovoltamperes (kVA) limits of the test facility. Readings of voltage, current, watts,
and torque shall be taken. For locked-rotor torque and current test, the locked-rotor condition shall be maintained
for 20 seconds at rated voltage unless locked-rotor torque and current values are obtained by 4.6.11.2. When
locked-rotor torque and current values are obtained from tests at less than rated voltage, the locked-rotor capacity
shall be demonstrated by 4.6.11.2. Tests shall be initiated with motor at room ambient temperature.
4.6.11.2 Test with motor operating at less than rated voltage. Locked-rotor torque and current values shall be
obtained with motor operating at the maximum kVA available at rated frequency. If the locked-rotor current varies
with rotor position, the rotor shall be locked in the position where the locked-rotor current is equal to the mean of
the maximum and minimum values. Readings of input voltage, current, watts, and torque values. The test shall be
repeated at voltages producing approximately half and one-quarter of the locked-rotor current measured at
maximum kVA. Input voltage, current, watts, and torque shall be measured. The proportion of current shall be
adjusted such that the minimum locked-rotor current shall be not less than the full-load motor current at rated load.
The locked-rotor current, corrected to rated voltage, shall be determined by the following equations:
For enclosed rotor slots:
I1r = I1 × (Vr / V1) β
where:
β = 0.7α + 0.35
and
α = log(I3 / I1) / log(V3/ V1)
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