a metal plate by the same holding method that will be used for mounting in
the enclosure. A specified current shall then be applied for a specified
period of time. After the filter has returned to room temperature, the
insulation resistance and voltage drop shall be measured. The insulation
resistance shall be measured using the method in paragraph ELECTROMAGNETIC
FILTERS. AC voltage drop measurements shall be made by using expanded
scale-type meters which will enable voltage differences of less than 1 volt
to be read. DC voltage drop measurements shall be made by using a dc
reading meter when the filter is carrying rated current and rated voltage.
The insulation resistance and the voltage drop will be measured after each
separate overload test. Filters will also be visually examined for
evidence of physical damage after each test.
2.6.5.6
Reactive Shunt Current Measurements
The reactive shunt current measurements shall be performed with the filters
mounted in the filter/ESA assembly enclosure or mounted on a metal plate by
the same holding method that will be used for mounting in the enclosure.
The filter shall be terminated in the inner compartment in an open circuit.
Rated ac voltage shall be applied between the filter outer compartment
terminal and the enclosure or metal plate. The ac current into the outer
compartment terminal shall be monitored. The measured current is equal to
the filter reactive shunt current.
2.6.5.7
Dielectric Withstand Voltage Test
The dielectric withstanding voltage test (also called high-potential, over
potential, voltage-breakdown, or dielectric-strength test) consists of the
application of a voltage higher than rated voltage for a specific time
between mutually insulated portions of a filter or between insulated
portions and ground. Repeated application of the test voltage on the same
filter is not recommended as even an overpotential less than the breakdown
voltage may injure the insulation. When subsequent application of the test
potential is specified in the test routine, succeeding tests shall be made
at reduced potential. When an alternating potential (ac) is used, the test
voltage shall be 60 Hz. and shall approximate a true sine wave in form.
All ac potentials shall be expressed as root-mean-square values. The KVA
rating and impedance of the source shall permit operation at all testing
loads without serious distortion of the waveform and without serious change
in voltage for any setting. When a direct potential (dc) is used, the
ripple content shall not exceed 5 percent rms of the test potential. A
voltmeter shall be used to measure the applied voltage to an accuracy of 5
percent. When a transformer is used as a high-voltage source of ac, a
voltmeter shall be connected across the primary side or across a tertiary
winding provided that the actual voltage across the filter will be within
the allowable tolerance under any normal load condition. Unless otherwise
specified, the test voltage shall be dc and shall be as follows:
a.
DC rated only - 2.5 times rated voltage.
b.
For filters with ac and dc ratings - 2.5 times rated dc voltage.
c.
AC rated only - 4.2 times rated rms voltage.
The duration of the dc test voltages shall be 5 seconds minimum, 1 minute
maximum, after the filter has reached thermal stability at maximum
operating temperature produced by passage of rated current. The test
voltage shall be applied between the case (ground) and all live (not
grounded) terminals of the same circuit connected together. The test
SECTION 13095A
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