FAA L830 Transformer Qualification

4.2.3 Insulation Resistance. The sample transformers shall be subjected to
a continuous 20-cycle test as follows:

4.2.3.1 Mating Connectors. Mating connectors that were gauged with "go" and
"no go" gauges shall be installed in the three connectors of the transformers.
The mating connectors shall not be removed before completion of the 20-cycle
testing. If they are removed for any reason, tests shall be repeated so that
the transformers and their connectors satisfactorily pass 20 continuous
cycles. One cycle shall consist of the sequence of operation specified in
paragraphs 4.2.3.2, 4.2.3.3, and 4.2.3.4.

4.2.3.2 Transformer. The transformers shall be operated, with mating
connectors installed, for a minimum of 6 hours in air at room temperature
with rated current flowing in primary coils. The secondaries of the
transformers shall be open-circuited. The procedure of this paragraph shall
hereinafter be referred to as "the heating cycle."

4.2.3.3 Water Immersion Test. Immediately following the heating cycle,the
transformers, with leads and connectors, shall be completely submerged in
water, which is grounded, at room temperature. Care should be taken to
insure that all molded connections, on transformer leads and test harness,
are completely immersed in water during this test. Immediately after
immersion, the insulation resistance of each coil and lead assembly shall be
measured. The time period between interruption of the heating cycle and
start of the measurement shall not exceed 3 minutes.

4.2.3.4 Soaking. The transformers and their connectors shall be soaked in
water, at room temperature, for not less than 12 hours, and the insulation
resistance measurements repeated.

4.2.3.5 Resistance Measurements. Measurements of dielectric and insulation
resistance shall be made with direct current. The test voltage shall be
applied for 1 minute between each coil and ground with the other coil
grounded and its connectors submerged in water. The insulation resistance
at the test voltage indicated shall equal or exceed the minimum values
specified in Table 2. Zero and maximum readings of the test instrument
shall be periodically checked by touching the high voltage lead to the
water surface and suspending it in air. After instrument needle settles
down following current inrush, it shall remain steady without fluctuations.