MIL-PRF-62284B(AT)
voltmeter shall be used to measure the applied voltage to an accuracy of at least 5%. Suitable
means shall be provided to indicate the occurrence of disruptive discharge, or an appropriate
indicator light or an overload protective device may be used for this purpose. As a result, verify
that there is no damage of dielectric material, otherwise shall constitute a failure. Upon
completion of the test, the test voltage shall be gradually reduced to avoid voltage surges. The
dielectric withstanding voltage test should be used with caution particularly in conformance
testing, as even an overpotential less than the breakdown voltage may injure the insulation and
thereby reduce its safety factor. Therefore, repeated application of the test voltage on the same
value is not recommended. Care should be taken to be certain that the test voltage is free of
recurring transients or high peaks.
4.2.3.4 Insulation resistance. To determine conformance to 3.3.3.2, insulation resistance
shall be measured prior to final assembly on the armature and field circuit. Measurements may
take 1 or 2 minutes to approach maximum insulation-resistance readings, provided the insulation
resistance is reasonably close to steady-state value. Unless otherwise specified, the measurement
error at the insulation-resistance value required shall not exceed 10%. Proper guarding
techniques shall be used to prevent erroneous readings due to leakage along undesired paths.
Verify that the resistance is not less than 50 megohms for the field circuit and for the armature
circuit including the insulated brush holders when used.
4.2.3.5 Transient voltage. To determine conformance to 3.3.3.3, operate the blower from
the indicated nominal operating voltage while applying the transient voltage for the time period
designated. Repeat each test pulse every six seconds for one minute.
TABLE III. Transient voltage test.
Blower voltage
Transient voltage
Nominal operating
with
time
voltage
transient voltage
(milliseconds,
(Vdc)
(Vdc)
ms)
+30
+40
50
+34
+70
700
+26
+14
20
+18
+4
50
Operate the blower from +24 Vdc power source and apply a negative voltage for two minutes, so
that the net voltage at the blower is -30 Vdc. After the above tests, the blower shall be subjected
to the performance tests of 4.2.3.1 and 4.2.3.2.
4.2.3.6 Starting current. To determine conformance to 3.3.3.4, the starting current test
shall be performed utilizing a power source having an effective impedance of 0.13 ± 0.01 ohm.
Verify that starting current does not exceed 60 A and drops to 10 A or less within one second
after application of input voltage.
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