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Megger test is an electric test used for measuring insulation properties in electrical power applications while contact resistance test measures the resistance of electrical connections.Contact resistance test is commonly known as ductor test.
The difference of the said equipment are as follows:
1. Megger Tester is used to measure the integrity of insulation of power cables, motor winding insulation, transformer windings, and generators at line to ground at most.The higher the value the less leakage current and good insulation. Low value results in poor insulation thats why maintenance is needed. This tester is used to impressed/apply voltage to the insulation of the equipment at specified voltage. Range of this tester are from250Vdc,500Vdc,1000Vdc, 2000Vdc & higher. Note: sometimes Meggering is confusing thats why it is not so much reliable.
2. Contact resistance tester could be a multimeter tester. This will only be used to determine the continuity of cables at terminals (end to end), joints, etc. This will also indicate if there are breaks, loose contact of cable from its joints or terminals. Indication will be that the higher the resistance the more you suspect that it is loose or break. The lesser or almost zero value indicates good contact of the cable to its terminal.
Megger test equipment and contact resistance meter test instruments serve different purposes in electrical testing. A Megger measures insulation resistance to assess the condition of cables and electrical equipment, crucial for preventing faults and ensuring safety. In contrast, a contact resistance meter focuses on measuring low resistance connections in switchgear, connectors, and circuit breakers to verify proper electrical conductivity. While both are essential for maintenance, they target distinct aspects of electrical system integrity: insulation quality versus connection reliability.
the megometer to test the insulation resistance between conductors and the metal portion of a casing of a device ,resistance meter is to test the value of a resistance and conductor's continuity.
megger is the insulation test which we supplied volt and measure insulation resistance
contact resistance is the test which i inject high ampere (200A and mesaure the resistance of contact
Megger testing is best for insulation test purposes, it is more accurate in finding3 phase motors and wires if it is grounded while resistance test is the best way to find out if the motor resistance is balance or not. Good motors should have a balance resistance.
Megger test equipment are high voltage and low current source devices used for measuring insulation resistance. These devices have very poor voltage regulation. Which means, if current increase, voltage rapidly drops , thereby keeping terminal voltage safe in case of short circuit detection in insulation test.
Contact resistance meter are low voltage high current source. Contact resistance is usually very low resistance. To get accurate measurement of contact resistance, it is important to pass higher current through contact under measurement to get significant voltage dropped across it and get fairly accurate reading.
