Question

A megger is used to measure ___________.
1. Medium resistance
2. Very low value of resistance
3. High value of resistance, Particular insulation resistance
4. Low value of resistance

Answer 1

Correct Answer - Option 3 : High value of resistance, Particular insulation resistance

Megger:

• Megger is a portable instrument to measure high insulation resistances.
• It works on the principle of electromagnetic induction.
• The electrical power to a megger is provided by a permanent magnet D.C. generator.
• The test voltages are usually of order 500, 1000, or 2500 V are generated by a hand-driven generator (permanent magnet D.C. generator).
• The operation of a megger is based on a moving coil meter.
• Earth pit resistance is measured with an earth tester, also called earth megger which can test the resistance across a range of currents and distances.
• Insulation megger is used to measure the insulation resistance of the cables.

 

Examples of High Resistance Materials:

• Cable Insulation Resistance.
• All Motors, generators, and transformers winding's insulation resistance.
• All semiconductor devices when reverse biased.

 

Methods to measure High Resistance:

• ​Loss of charge method.
• Direct-Deflection method.
• Mega ohm Bridge.
• Megger.