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Inspection of transformer after shock test |
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|  MIL-T-15108C(NAVY)
4.6.8.3 Duration of test. The heating test for transformers shall be continued until
constant temperatures have been attained in all parts of the transformer.
4.6.8.4 Method of loadinq. The following methods of loading transformers for the
heating test are acceptable (see figure 5):
(a) The transformer may be loaded directly with rated voltage applied
to the primary and sufficient load on the secondary to load the
transformer to rated kVA capacity.
(b) Duplicate single-phase transformers may be tested in banks of two
by connecting both the high-voltage. and low-voltage windings in
parallel and by applying rated excitation voltage at rated fre-
quency to one set of paralled windings. Connections of the other
pair of windings shall be opened at one point and a voltage
impressed across the break just sufficient to circulate rated
currents through the windings. The circulated current should
preferably be at rated frequency.
If other than rated frequency is applied to the opened windings the value of
Note:
current should be adjusted to yield the true impedance watts of the transformer.
Measurement of the ambient temperature
4.6.8.5 Measurement of the ambient temperature.
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shall be in accordance with the requirements of MIL-E-917.
4.6.9 Weight and volume. The weight and volume of a transformer shall be taken and
recorded. The design weight appears on the drawing. Weight of transformers of the same
size and design may exceed the value shown on the drawing by 5 percent, but shall not exceed
the weight value specified in table II.
4.6.10 Shock.
4.6.10.1 General.
The shock test shall be in accordance with grade A, class I, type A
of MIL-S-901.
The transformers shall be mounted on the shock machine in the
4.6.10.2 Mounting.
following manner:
(a) Light-weight machine - Figure 4A of MIL-S-901 (1 through 37.5 kVA).
(b) Medium-weight machine - Figure 9-1 of MIL-S-901 (50 through 100 kVA).
4.6.10.3 Inspection of transformer after shock test. After the shock test, the trans-
former shall be carefully inspected for damage. Details of all damage shall be recorded.
If there are any appreciable injuries, it will be considered that the transformer has failed
to meet the requirements of this test.
4.6.10.3.1 Electrical tests. After the mechanical inspection, the transformer shall
be subjected to the following electrical tests in the order listed:
(a)
No-load losses (see 4.6.5.1).
(b)
Exciting current (see 4.6.6).
(c)
Short circuit (see 4.6.13).
(d)
Dielectric (see 4.6.11).
If the values of no-load loss watts and the exciting current amperes differ by more than
plus or minus 5 percent and 10 percent, respectively, from the original values, it shall
be cause for rejection. Failure of the transformer to meet the requirements of the short
circuit test or the dielectric test shall also be sufficient cause for rejection.
4.6.11 Dielectric strength test.
4.6.11.1 General. The dielectric strength test shall be performed following the com-
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pletion of all but the weight and shock tests. This test shall be made on the completely
assembled transformer at equipment temperature between 10C and 50C.
4.6.11.2 Applied potential. Test voltage shall be applied successively between each
winding with all other windings and metal parts grounded.
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