COUPLING TO TEST GENERATORS BASIC TUTORIALS



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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