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|  MIL-M-17413A(NAVY)
4.2.4.11 Insulation resistance (cold). - This test shall be made before the delectric tests. Prior
to the application of the test voltage, the windings of the motor shall be thoroughly discharged by con-
necting the windings to the frame. Separate measurements shall be made on the field and armature
windings. Circuits of equal voltage above ground shall be connected together. Circuits or groups of
circuits of different voltage above ground shall be separated. Insulation resistance shall be measured
with an insulation-resistance-indicating instrument conforming to type GC of Specification MIL-O-16485.
The time of test voltage application shall be not less the 60 seconds The temperature of the motor
windings at the time of the test shall be measured and recorded. Insulation resistance measurements shall
be corrected to 25C. Unless otherwise specified in the contract or order, corrections shall be made on
the basis of insulation resistance doubling for each 15C. decrease in temperature. The relative humidity
at the time of the test shall be measured and recorded.
4.2.4.12 Dielectric tests. -
4.2.4.12.1 General. - The dielectric test shall be made after all other tests have been completed.
If the insulation resistance of the windings is known to be lower than specified, due to dirt or moisture
or damage to windings, this shall be remedied before the application of the dielectric test voltage. The
dielectric test shall be made on the completely assembled machine and not upon individual parts. An
exception is made in the case of repair parts which require dielectric tests; for example, coils and
rotating elements with insulated windings.
4.2.4.12.1 Measurement of test voltage. - The measurement of the voltage used in dielectric tests
shall be made by the voltmeter method whereby the instrument derives its voltage from the high-voltage
circuit either directly or by means of a voltmeter coil placed in the testing transformer, or through an
auxiliary ratio transformer. In any case, if the capacitance of the machine to be tested is such as to
cause wave distortion, the testing voltage shall be checked by a crest-voltage meter. If the crest-voltage
meter is calibrated in crest volts, its reading shall be reduced to the corresponding root mean square
sinusoidal value by multiplying by O. 707.
4. 2.4.12.3 Points of application. - The test voltage shall be successively applied between each
electric circuit and all other electric circuits and metal parts grounded. The test voltage shall be applied
in such a manner as to preclude the possibility of pitting the bearings in case of insulation failure.
Voltage need not be applied between stationary and rotating windings.
4.2.4.13 Effectiveness of enclosure. - Motors shall be tested as specified in Specifica-
tion MIL-E-2036 except that hose test of dripproof enclosures is waived.
4.2.4.14 Overload and heat run test. -
4.2.4.14.1 Overload tests. - The overload test shall be made at 150 percent rated load only on
continuous-duty motors in accordance with the following: Start with motor cold and record temperature
at end of run. Temperature rises shall not exceed those specified for continuous operation at rated load.
The conditions of test shall be as follows:
Rated motor load - 150 percent.
Voltage - Rated.
Time - 10 minutes.
4.2.4.34.1.1 The permissible temperature rises specified in 3.6.1.2 shall not be exceeded. Unless
specified (see 6.2) overload tests for submarine motors are not required.
4. 2.4.14.2 Heat-run test. - The heat run test shall be made on continuous duty motors in accordance
with the following:
Rated motor load - 100 percent.
Voltage - Rated. (For submarine service - the test shall be conducted at nominal and
extremities of the voltage range (see 3.6.1.14 (q) (12) and 3.7.1. 1).
Time - All temperatures are constant.
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