This Portion of Electrical andElectronic Measurements and Measuring instruments contains Measurement of Energy and industrial Metering MCQs (Multiple Choice Questions and Answers) / Objective Type Questions and Answers.
This Section covers below lists of topics.
- Motor Meters
- Braking
- Friction
- Energy Meters for A.C Circuits
- Theory of induction type meters
- Single phase induction type meters
- Polyphase energy meters
- Industrial Metering and Tarifs
- Maximum Demand indicators
- Measurements of Vah and VArh
- VArh Metering
- Testing of Energy meters
PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE
1. The breaking torque provided by a permanent magnet in a single phase energy meter is proportional to the
- Square of the flux of the permanent magnet
- Speed of the meter
- Distance of the permanent magnet from the centre of revolving disc
- All the above.
D. All the above.
2. The breaking torque provided by a permanent magnet in a single phase energy meter can be changed by :
- Providing a magnetic shunt and changing its position
- Changing the distance of the permanent magnet from the centre of the revolving disc
- Both a and b
- None of the above.
C. Both a and b
3. In the single phase induction meter, in order to obtain true value of energy, the shunt magnet flux should lag behind the applied voltage by :
- 90°
- 0°
- 45°
- None of the above.
A. 90°
4. In an induction type of meter, maximum torque is produced when the phase angle, between the two fluxes is :
- 0°
- 45°
- 60°
- 90°
D. 90°
5. In an induction type meter, maximum torque is obtained when the parameters of rotating disc are _______ Where R and X are respectively the resistance and reactance of eddy current paths in the disc.
- R=0
- X=0
- R=X
- None of the above.
B. X=0
6. In a single phase induction type energy meter, the lag adjustment is done :
- To make the coil flux to lag 90° behind the applied voltage
- To make the pressure coil flux to lag 90° behind the applied voltage
- To bring the pressure coil flux in phase with the applied voltage
- None of the above.
B. To make the pressure coil flux to lag 90° behind the applied voltage
7. In a circuit of single phase induction energy meter, the pressure coil lags the voltage by 88°, the errors while measuring power in two circuits having power factor of unity and 0.5 lagging are respectively are :
- – 0.061% , + 6.1%
- + 0.061% , - 6.1%
- - 0.061% , - 6.1%
- None of the above.
C. - 0.061% , - 6.1%
8. Phantom loading for testing of energy meters is used :
- To isolate the current and potential circuits
- To reduce power loss during testing
- For meters having low current ratings
- To test meters having a large current rating for which loads may not be available in the laboratory. This also reduces power losses during testing.
D. To test meters having a large current rating for which loads may not be available in the laboratory. This also reduces power losses during testing.
9. In an induction type energy meter, compensation for static friction is provided by
- Shading bands which are actuated by to provide a constant torque irrespective of load
- Lag circuits
- Drilling holes in the disc
- None of the above.
A. Shading bands which are actuated by to provide a constant torque irrespective of load
10. In a household single phase single phase induction type wattmeter, the meter can be reversed by
- Reversing the supply terminals
- Reversing the load terminals
- Opening the meter connections and reversing either the potential coil terminals or current coil terminals
- Opening the meter and reversing connections of both current and potential coil circuits.
C. Opening the meter connections and reversing either the potential coil terminals or current coil terminals
11. If an induction type energy meter runs fast, it can be slowed down by :
- Lag adjustment
- Light load adjustment
- By adjusting the position of braking magnet and making it come closer to the centre of the disc
- By adjusting the position of braking magnet and making it move away from the center of the disc.
D. By adjusting the position of braking magnet and making it move away from the center of the disc.
12. Creeping in the single phase induction type energy meter may be due to :
- Overcompensation for friction
- Overvoltage
- Vibrations
- All the above.
D. All the above.
13. A Merz price maximum demand indicator indicates :
- Maximum demand
- Average maximum demand over a specified period of time
- Maximum energy consumption
- All the above.
B. Average maximum demand over a specified period of time
14. Vah metering can be done by using :
- A ball and disc friction gearing
- Trivector meter
- Bridge connected rectifiers
- All the above.
D. All the above.
15. Light load adjustment for induction type energy meters are usually done at :
- 10% of full load current
- 5% of full load current
- 50% of full load current
- 1% of full load current.
B. 5% of full load current
16. Energy meters do not have a control spring to
- avoid unnecessary friction losses
- enable continuous rotation of the disc
- avoid damping during movement
- all of the above
B. enable continuous rotation of the disc
17. In induction-type energy meters, the speed of rotation of the disc is proportional to the
- energy consumption
- power consumption
- derivative of power consumption
- none of the above
B. power consumption
18. The advantages of induction-type energy meters are
- low torque/weight ratio
- low friction
- high and sustained accuracy
- all of the above
A. low torque/weight ratio
19. Induction-type energy meters have aluminum disc as the rotating part so that
- flux can pass through the rotating part
- eddy current can be induced in the rotating part
- creeping error can be avoided
- all of the above
B. eddy current can be induced in the rotating part
20. In induction-type energy meters
- pressure coil is the moving part
- current coil is the moving part
- both current and pressure coils are moving
- both current and pressure coils are stationary
D. both current and pressure coils are stationary
21. In induction-type energy meters, high driving torque can be obtained by
- making the disc purely resistive
- making the phase difference between the two operating fluxes as large as possible
- making the disc impedance as low as possible
- all of the above
A. making the disc purely resistive
22. Braking torque provided by the permanent magnet in an induction-type energy meter is proportional to
- speed of the rotating disc
- square of the flux of the permanent magnet
- distance of the permanent magnet with respect to centre of the disc
- all of the above
C. distance of the permanent magnet with respect to centre of the disc
23. Braking torque provided by the permanent magnet in an induction-type energy meter can be changed by
- providing a metal shunt and shifting its position
- moving the position of the permanent magnet with respect to the disc
- both (a) and (b)
- none of the above
C. both (a) and (b)
24. In single-phase induction-type energy meters, maximum torque is produced when the shunt magnet flux
- leads the supply voltage by 90°
- lags the supply voltage by 90°
- lags the supply voltage by 45°
- is in phase with the supply voltage
B. lags the supply voltage by 90°
25. In single-phase induction-type energy meters, lag adjustments are done by
- permanent magnet placed on the edge of the disc
- holes provided on the side limbs of the pressure coil
- copper shading bands placed on the central limb of the pressure coil
- metal shunts placed on the series magnets
C. copper shading bands placed on the central limb of the pressure coil
26. In single-phase induction-type energy meters, lag adjustments can be done by
- shifting the copper shading band along the axis of the central limb
- varying the external resistance connected to the shading coil placed on the central limb
- either of (a) or (b) as the case may be
- none of the above
C. either of (a) or (b) as the case may be
27. In single-phase induction-type energy meters, friction compensation can be done by
- placing shading bands in the gap between central limb and the disc
- drilling diametrically opposite holes on the disc
- providing holes on the side limbs
- all of the above
D. all of the above
28. Creeping in a single-phase energy meter may be due to
- vibration
- overcompensation of friction
- over voltages
- all of the above
B. overcompensation of friction
29. Creeping in a single-phase energy meter can be avoided by
- using good quality bearings
- increasing strength of the brake magnet
- placing small soft iron piece on edge of the rotating disc
- all of the above
C. placing small soft iron piece on edge of the rotating disc
30. Increase in operating temperature in an induction-type energy meter will
- reduce pressure coil flux
- reduce braking torque
- reduce driving torque
- all of the above
D. all of the above
31. Overload errors in induction-type energy meters can be reduced by
- designing the meter to run at lower rated speeds
- designing the current coil flux to have lower rated values as compared to pressure coil flux
- providing magnetic shunts along with series magnets that saturate at higher loads
- all of the above
D. all of the above
32. Over voltages may hamper rotation of the disc in induction-type energy meters since
- the pressure coil flux no longer remains in quadrature with the current coil flux
- dynamically induced emf in the disc from the pressure coil flux produces a self-braking torque
- effect of the brake magnet is enhanced
- all of the above
B. dynamically induced emf in the disc from the pressure coil flux produces a self-braking torque
33. If an induction-type energy meter runs fast, it can be slowed down by
- moving up the copper shading bands placed on the central limb
- adjusting the magnetic shunt placed on the series magnets
- moving the permanent brake magnet away from centre of the disc
- bringing the permanent brake magnet closer to centre of the disc
D. bringing the permanent brake magnet closer to centre of the disc
34. Phantom loading for testing of energy meters is used
- for meters having low current ratings
- to isolate current and potential circuits
- to test meters having a large current rating for which loads may not be available in the laboratory
- all of the above
C. to test meters having a large current rating for which loads may not be available in the laboratory
35. In single-phase induction-type energy meters, direction of rotation of the disc can be reversed by
- reversing supply terminals
- reversing load terminals
- opening the meter and reversing either the potential coil terminals or the current coil terminals
- opening the meter and reversing both the potential coil terminals and the current coil terminals
C. opening the meter and reversing either the potential coil terminals or the current coil terminals
