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Section 1
An Introduction to Impulse Testing with the MegaPulse CDN 240/8
The impulse test is designed to simulate impulse surges which occur in everyday life due to nearby lightning strikes,
switching transients, and other high-frequency faults on the power distribution network. Impulse testing is the
fundamental method for empirical verification of the adequacy of insulation. The impulse test is performed to ensure
that the insulation in question will be able to function properly when subjected to similar impulse surges in the field.
•The MegaPulse CDN 240/8 is designed to allow surge testing to be conducted on the mains line of operating
equipment. The CDN is designed to EN 61000-4-5 Figure 7 and protects the attached Surge Tester outputs
from line voltage, and the mains voltage generator from the Surge Tester outputs.
•The MegaPulse CDN 240/8 does not generate surge voltages.
•Connection of a surge tester to the INPUT jacks and the appropriate mains voltage for the DUT is required.
•The mains input of the DUT is connected to the OUTPUT jacks of the MegaPulse CDN 240/8.
•The MegaPulse CDN 240/8 is suitable for use with 120V/8A max or 220-240V/8A max 50/60Hz mains
voltages.
Safety Precautions
An impulse withstand test can generate high voltages at potentially lethal current levels. Currents of as little
as 5 mA at 120 volts can cause death; and any MegaPulse model can deliver lethal current levels for a very short time
duration. The potential for serious injury or death exists and personnel should be aware when they conduct this test.
All inputs and outputs of the MegaPulse CDN 240/8 should be considered hazardous. The front panel input and output
jacks contain the surge pulse; the rear panel is connected to mains voltage and is to be considered hazardous as well.
Test Personnel
Personnel require special training to conduct the impulse test. They should understand electrical
fundamentals clearly, and be aware that high voltage is adept and creative at completing a path to ground. Instructions
should include a warning against any metal jewelry. Operators should not allow others in the testing area, especially
when tests are being conducted. Organization is to be stressed. The operator should keep the area free of unused
leads and equipment.
Testing Area
The area used for conducting the dielectric withstand test should be as remote as possible from normal
production line activities. Only personnel actually conducting the test should be allowed in the area, and it should be
taped or roped off to preclude casual entry by other employees. In addition, the area should be marked "WARNING
- HIGH VOLTAGE TESTING" or the equivalent to warn others of the nature of the testing taking place.
The bench being used should be non-conductive, and any exposed metal parts should be tied together and
grounded. If a conductive surface must be used, it should be grounded.
Because of sparking during an impulse test failure, it is not safe to conduct impulse testing in combustible
atmospheres.
It is imperative that a good ground be provided to the MegaPulse CDN 240/8. Before connecting the
equipment, ensure that the building wiring provides a low-resistance ground. If the MegaPulse tester is used on a
high-resistance grounding circuit, dangerous high voltages may be present to the operator. In addition, the power to
the Testing Area should be provided with an easily reached shutoff switch which can be actuated by personnel outside
the Area if needed.
