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Acceptable method of mounting on shock-testing machine |
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|  MIL-M-17413A(NAVY)
(d) A definition of "failure to perform principal functions".-
Breakage of any parts, including mounting bolts.
(2) Appreciable distortion or dislocation of any parts such as mouting feet,
poles, coils, brushes, and bearings.
(3) A value of insulation resistance (corrected to 25C. less than that
permitted by 3.2,10,
(4) A mechanical unbalance of more than two times the value of unbalance
specified in 3.2.12.1.
(5) A bearing temperature rise in excess of that permitted in table V.
(8) Objectionable noise. Any noticeable increase or decrease in noise of
the motor when operating at rated speed should be investigated and
its cause determined. However, if disassembly is required for this
check, it should be made during the test specified in 4.2.4.22 (d) (8).
(7) Low dielectric strength. The motor shall be operated to obtain
approximately related temperature rise of iron and windings, then
disconnected from its load or from its source of power and a
dielectric strength test made to check the condition of the insulation.
This dielectric strength test shall be made in accordance with 4.2.4.12
except that it shall be made with an applied voltage equal to 65 percent
that specified in 4.2.4.12. Under these conditions, insulation failures
shall be cause for rejection.
(8) Failure to pass inspection. The motor shall be disassembled following
checks 4.2.4.22 (d) (1) to 4.2.4.22 (d) (7), Inclusive, and inspected
thoroughly for damage. The extent of disassembly need be only to the
point where the condition of the motor can be easily observed. The
effects of the shocks and subsequent check tests on the structure,
bearings, and insulation shall be carefully observed and recorded.
(e) Acceptable method of mounting on shock-testing machine. - The mounting adapters
shown on the following figures of Specification MIL-S-901 shall be used:
(1) Figure 4C for motors to be tested on the shock-testing machine for
lightweight equipment.
(2) Figure 7A for motors to be tested on the shock-testing machine for
medium weight equipment.
(3) For heavy weight equipment, the methods of mounting shall be as
specified in Specification MIL-S-901.
(f) Exceptions to Specification MIL-S-901. - None.
(9) Place at which shock test will be conducted. - At the manufacturer's plant. Where
a manufacturer is unable to conduct these tests at his own plant, he may arrange to
have them conducted it a commercial laboratory, or Government laboratory suitably
equipped to conduct tests. Where shock tests are conducted at a Government labora-
tory, a copy of the applicable master drawing shall accompany the motor.
(h) Number of motors to be tested. - Unless otherwise specified in the contract or
order, one motor of the longest core length in each diameter and of similar
construction out of each group of enclosures listed below, shall be shock-tested:
Group 1:
Open.
Protected.
Dripproof.
Dripproof protected.
Splashproof protected.
Group 2:
Spraytight
Watertight
41
Totally enclosed
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