Application of the test wave to the
relay under test shall be done using coupling/isolating networks or
capacitive coupling clamps as described following.
Coupling/isolating networks
This method shall be used when testing
current, voltage, power supply, input circuit, or output external
connection groups.
Capacitive coupling clamp
The capacitive coupling clamp is
intended as a means for coupling test waveforms to shielded and other
circuits where direct galvanic connection to the equipment under test
(EUT) terminals may impair operation.
Typical use of the clamp for common
mode tests is shown in Figure 7. The use of the capacitive clamp
shall be limited.
The capacitive clamp consists of two
conductive surfaces (made of galvanized steel, brass, copper, or
aluminum) insulated from each other by means of high quality
insulating supports.
The coupling effect is established by
placing an insulated cable (feeding the signals to the device under
test) through the V shaped duct on top of the clamp, and subsequently
closing the clamp as much as possible in order to maximize the
coupling capacitance between the clamp and the cable.
The lower conductive surface of the
clamp shall be placed on (and solidly connected to) a ground plane
with a minimum area of 1 m2. The reference ground plane shall extend
beyond the clamp by at least 0.1 m on all sides.
The high voltage coaxial connector
intended for connection to the test generator may, for convenience,
be provided on both ends of the clamp. Regardless of the design
however, during the test, the generator shall be connected to that
end of the clamp that is nearest to the device under test.
Due to high voltages involved, the
external insulation on the cable to which the transients are being
coupled must be capable of withstanding a 5 kV 1.2/50 μs pulse.
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