Electrical Measurements and Instruments (EX-303) - Important Questions

Explain the static and dynamic characteristics of measuring instruments / measurement systems in detail with suitable examples.

Explain the construction and working principle / operation of the D'Arsonval galvanometer and its use as a basic measuring instrument.

Describe the construction and working of a ballistic galvanometer and explain the constructional differences from a D'Arsonval galvanometer.

What are the different types of errors in measurement? Explain their classification, sources and methods for reduction.

Explain how the range of a PMMC / galvanometer instrument is extended to act as ammeter and voltmeter, deriving the shunt and multiplier expressions.

Explain the construction of current transformer (CT) and potential transformer (PT) with principle and applications.

Explain PMMC, MI and electrodynamometer type instruments and compare their construction, working principles, advantages and disadvantages.

Explain design modifications / steps taken for minimizing / reduction of errors in potential transformer.

Explain the construction and working of two-element (double-element) dynamometer type wattmeter for three-phase systems, including three-element type.

Explain errors in electrodynamometer type wattmeter including stray magnetic field error and remedial measures.

A 50 A, 230 V single-phase energy meter on full load test makes 61 revolutions in 37 seconds. If the normal disc speed is 520 revolutions per kWh, determine the percentage error. Also explain testing by phantom loading.

Explain the construction and working of a three-phase AC energy meter with circuit and phasor diagram.

Describe the construction and working of a 3-phase electrodynamometer / alternating-field power factor meter. Also discuss single-phase and moving-iron types.

Explain principle, theory and derivation of Kelvin's double bridge for low resistance measurement and explain how contact and lead resistances are eliminated.

Describe the experimental method for determination of B-H curve / hysteresis loop of a magnetic specimen, e.g. method of reversals, step-by-step method.

Describe the Lloyd-Fisher square method for measurement of iron / power loss in ferromagnetic (transformer steel strip) material using the wattmeter method.