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MIL-T-15108C(NAVY)
4.5 Test reports, procedures, and calculations. The supplier shall prepare test
reports, procedures, and calculations in accordance with the data ordering document included
in the contract or order (see 6.2.2) and shall include unique features specified in 4.5.1.
#
4.5.1 Qualification inspection.  Three copies of the test report shall be submitted
to NAVSEC. A separate report shall be prepared for each transformer including a report
number, date and authentication by the cognizant Government representative.  The report
shall show the tests in sequence as shown in the specification and in a table form.  The
table shall show the test, test value recorded and the applicable specification limit.
Supplemental sheets shall show calculations for various tests such as regulation, heating,
inrush current, short circuit, etc.
4.6 Test methods.
4.6.1 Resistance.  Resistance of both the primary and secondary windings shall be
#
accurately measured. Temperature at which the resistance readings are taken shall also be
recorded.
4.6.2 Polarity.  Polarity of each transformer shall be determined by either of the
methods specified in 4.6.2.1 and 4.6.2.2 at the manufacturer's option.
4.6.2.1 Polarity by alternating voltage. The left-hand side facing the low-voltage side
of the transformer high-voltage and low-voltage outlet leads shall be connected together.
Any convenient value of alternating voltage not exceeding rated voltage shall be applied to
the high-voltage winding.  Readings of the applied voltage and voltage between the right-
hand adjacent high-voltage and low-voltage leads shall be observed.  If the latter voltage
reading is less than the former indicating the approximate difference in voltage between
that of the high-voltage and low-voltage windings, the polarity is subtractive.  If the
latter is greater than the former, the polarity is additive.
4.6.2.2 Polarity by standard transformer.  A standard transformer of known polarity
and having the same ratio as the transformer to be tested may be used. High-voltage windings
of both transformers shall be connected in parallel.  Left-hand side low-voltage leads facing
the low-voltage side-of both transformers shall be connected together. Right-hand side leads
shall be left free. With these connections, a reduced value of voltage shall be applied to
the high-voltage windings and the voltage between the two free leads shall be measured. A
zero or negligible reading of the voltmeter will indicate that the relative polarities of
both transformers are identical.
4.6.3 Ratio.  Turn ratio between the primary and the secondary windings shall be accu-
rately determined by either of the methods specified in 4.6.3.1 and 4.6.3.2 at the manufac-
turer's option.
4.6.3.1 Voltmeter method. The ratio test shall be made with rated or lower voltage
at rated or higher frequency applied to either the high- or low-voltage leads of the trans-
former. Simultaneous readings of a voltmeter in the high-voltage winding and a voltmeter
in the low-voltage winding shall be taken and recorded.  Meters shall be interchanged and
another set of readings obtained; the average of these two sets of readings shall be used
in checking the ratio.
4.6.3.2 Standard transformer method.  The transformer to be tested shall be connected
in parallel with a standard transformer of the same nominal ratio.  Secondaries shall also
be connected in parallel but with a voltmeter or detector in the connection between two
terminals of similar polarity and so arranged as to read the difference between the two
secondary voltages.  If the manufacturer desires, the voltages in each secondary winding
may be obtained.  When this method is used, however, the voltmeters shall be interchanged
and a second set of readings shall be obtained.  The average of the results shall be used
in determining the ratio.
#
4.6.3.2.1 Connections for the ratio test by comparison with a standard transformer
are shown on figure 4.
4.6.3.2.2 The variation of the value of ratio between transformers of the same size,
#
design, and type shall be within plus or minus one-half of 1 percent of turns ratio shown
on the applicable drawing.
9

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