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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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The application of a megger is _________
to measure resistance
to test for leakage
to limit the current
to increase the emf of the circuit
to test for leakage
Quick Summary: A Megger (megohmmeter) is a specialized portable instrument used primarily to measure high values of insulation resistance. It determines the integrity of electrical insulation in cables, transformers, motors, and generators by detecting leakage currents that occur due to insulation breakdown.
A Megger (megohmmeter) is a specialized portable instrument used primarily to measure high values of insulation resistance. It determines the integrity of electrical insulation in cables, transformers, motors, and generators by detecting leakage currents that occur due to insulation breakdown.
R=IV — Ohm's law applied for insulation resistance measurement
Td∝IV — Deflecting torque is proportional to the ratio of voltage and current
The Megger operates on the principle of electromagnetic deflection. It typically consists of a hand-driven DC generator (usually 500V or 1000V) and a permanent magnet moving coil instrument with two coils (deflecting and control) mounted at a fixed angle. When the generator is cranked, a high voltage is applied across the insulation; the resulting current produces a deflecting torque, and the ratio of voltage to current determines the insulation resistance displayed on the scale.
Meggers use high DC voltages to detect tiny leakage currents (micro-amperes or nano-amperes).
A hand-cranked generator ensures that no external power supply is needed for field testing.
The instrument scale is calibrated in Mega-ohms (MΩ).
A guard terminal is often provided to bypass surface leakage currents for more accurate results.
Self-powered (no external batteries required)
Robust and portable for field use
Direct reading of high resistance values
High voltage can be dangerous if not handled correctly
The reading may fluctuate if cranking speed is inconsistent
Sensitive to external moisture and dust
Insulation resistance testing of electric motors
Cable fault detection
Transformers and power system maintenance
Verification of ground connections
A reading of 'Infinity' indicates perfect insulation, while 'Zero' indicates a short circuit.
Option A is too broad as resistance can be measured by other devices like Multimeters (Low R) or Wheatstone bridges.
Option C refers to current-limiting resistors (ballasts) or inductors, not measurement tools.
Option D is incorrect as the Megger is a measuring device, not an active source for boosting circuit EMF.
B is correct — A megger is specifically designed to measure high insulation resistance and test for leakage currents in electrical systems.
Always remember that while a Multimeter measures low resistance, a Megger is strictly for high resistance/insulation testing. Never use a Megger on sensitive electronic circuits as the high voltage can damage solid-state components.