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A dynamometer wattmeter can be used for both D.C. and A.C.

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Answer :

The resistance in the circuit of the moving coil of a dynamometer wattmeter should be high.

Description :

The potential coil of a single phase dynamometer wattmeter has 4840 Ohm resistance. Voltage across the load is 220 V. With the potential coil connected on the load side, the meter indicates 100 W. Approximate percentage error due to wattmeter connection is (A) 11% (B) 9% (C) 1.1% (D) 3%

Answer :

The potential coil of a single phase dynamometer wattmeter has 4840 Ohm resistance. Voltage across the load is 220 V. With the potential coil connected on the load side, the meter indicates 100 W. Approximate percentage error due to wattmeter connection is 11%

Description :

State the effects of errors in dynamometer type wattmeter due to i) pc- inductance ii) pc- capacitance iii) mutual inductance iv) Connection.

Answer :

Errors in wattmeter:  i) pc - inductance: Pressure coil inductance causes wattmeter to read more power than actual .  ii) pc-capacitance: The wattmeter reads less power.  iii) ... iv) Connection: In uncompensated wattmeter , the reading of wattmeter includes the powerloss in coils. 

Description :

State any four errors that occur in dynamometer type wattmeter

Answer :

Errors that occur in dynamometer type wattmeter: 1. Errors due to method of connection. 2. Error due to pressure coil inductance. 3. Error due to pressure coil Capacitance. 4. Error due to mutual ... Error due to eddy currents. 7. Temperature error. 8. Error due to vibration of moving system

Description :

With neat diagram explain constructional details of dynamometer type wattmeter.

Answer :

Working Principle of Wattmeter: It consists of two stationary coils, called current coils and one moving coil, called voltage or potential coil. The moving coil is mounted on the spindle, in the gap ... experiences a force and tends to move in the direction as per Fleming's left hand rule. 

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Answer :

An induction wattmeter can be used for A.C. 

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In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at 120°.

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The pressure coil of a wattmeter should be connected on the supply side of the current coil when load impedance is high.

Description :

With a neat sketch explain working of 1 phase dynamometer type power factor meter.

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Working of 1 phase dynamometer type power factor meter : The current coil is connected in series with load. Two pressure coils marked as A and B are connected across the supply terminals ... becomes stationary and the pointer shows steady deflection corresponding to the power factor of the load. 

Description :

In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be?

Answer :

In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be 0.5.

Description :

In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The power factor of the load was?

Answer :

In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The power factor of the load was unity.

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In a low power factor wattmeter the compensating coil is connected in series with pressure coil.

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Answer :

In a low power factor wattmeter the pressure coil is connected to the load side of the current coil.

Description :

The torque produced in wattmeter is proportional to

Answer :

A

Description :

List the different errors in wattmeter & explain compensation for it.

Answer :

Errors in Wattmeter Compensation method Error due to connection method To overcome this error, wattmeters are provided with additional compensating winding which is connected in series with ... due to friction The weight of moving system be reduced to minimum possible.

Description :

Use Voltmeter, ammeter, wattmeter to determine active, reactive and apparent power consumed in given R-L series circuit, draw phasor diagram.

Answer :

Practical Significance In the industry environment Electrical Engineering diploma graduate are expected to measure basic parameters like voltage, frequency, time period etc. for R-L series circuits. Therefore ... /varying L. 7. Draw the phasor diagram for each of reading for verification.

Description :

State the principle of wattmeter. 

Answer :

Working Principle of Wattmeter: It consists of two stationary coils, called current coils and one moving coil, called voltage or potential coil. The current coils are connected such that they ... experiences a force and tends to move in the direction as per Fleming's left hand rule. 

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Merits of two wattmeter method

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Advantages of Two Wattmeter Method for 3-Phase Power Measurement: 1) It is used for balanced as well as unbalanced load. 2) For the star type load, it is not necessary to ... reactive volt-amperes for balanced loads also. 7) The circuit connections are independent of load connection.

Description :

Compare CC and PC of wattmeter on the basis of:- (i) Connection (ii) Status (iii) Number of turns (iv) Gauge of wire.

Answer :

Particulars Current coil (CC) Pressure coil (PC) Connection Connected in series with load Connected in parallel with load Status It is fixed coil in wattmeter It is moving coil in ... number of turns It is having more number of turns Gauge of wire Less More

Description :

State any two disadvantages of one wattmeter method of measurement of 3 phase power.

Answer :

State any two disadvantages of one wattmeter method of measurement of 3 phase power. Disadvantages of one wattmeter method:- 1. Only used for balanced load 2. It can not be used for ... connection then neutral point must be available 4. Delta connection must be opened to connect current coil.

Description :

State various types of errors in wattmeter.

Answer :

Types of Error in wattmeter: 1. Errors due to method of connection. 2. Error due to pressure coil inductance. 3. Error due to pressure coil Capacitance. 4. Error due to mutual inductance effect. 5. ... . Error due to eddy currents. 7. Temperature error. 8. Error due to vibration of moving system.

Description :

Explain construction & working of electrodynamometer type wattmeter.

Answer :

Electrodynamometer Type Wattmeter:  Construction: It essentially consists of the fixed and moving coil. The fixed coil is split into two equal parts which are placed close together and parallel to each other. ... hence these instruments can be used for measurement of A.C. & D.C. power.

Description :

List one advantage and one disadvantage of one wattmeter method. 

Answer :

Advantages:  1) Only one wattmeter is used.  2) Less number of connections.  3) Cost required is less.  Disadvantages:  1) Used only for 3- Φ balanced load and not for ... be accessible for connecting the Pressure coil.  3) Delta connection must be opened to connect current coil. 

Description :

If a dynamometer wattmeter is connected in an ac circuit, the power indicated by the wattmeter will be (a) volt-ampere product (b) average power (c) peak power (d) instantaneous power 

Description :

The pressure coil of a dynamometer type wattmeter is  A) Highly inductive B) Highly resistive C) Purely resistive D) Purely inductive

Answer :

b

Description :

 In dynamometer type of wattmeter, which of the coil is split up into two parts?

Answer :

 In dynamometer type of wattmeter, which of the coil is split up into two parts?  current coil

Description :

Draw and explain the circuit diagram for measurement of single phase power using dynamometer type wattmeter. 

Answer :

Circuit diagram for measurement of single phase power using dynamometer type wattmeter: Explanation: It consists of two stationary coils, called current coils and one moving coil, called voltage or ... i.e. power. The meter can be calibrated directly to indicate the power in watts. 

Description :

Measurement of power and power factor of a 3-phase system by two wattmeter method can be obtained in case of  1. Balanced load and balanced source  2. Balanced source with 3-phase 3-wire unbalanced load  3. Unbalanced source with 3-phase 3-wire balanced load  4. Balanced source with 3-phase 4-wire unbalanced load  5. unbalanced and unbalanced source    (a) 1 only (b) 2, 3 and 5 (c) 1, 2, 3, 4 and 5 (d) 1, 2, 3 and 5 

Answer :

Measurement of power and power factor of a 3-phase system by two wattmeter method can be obtained in case of  1. Balanced load and balanced source  2. Balanced source with 3-phase 3-wire unbalanced load  3. Unbalanced source with 3- ... b) 2, 3 and 5 (c) 1, 2, 3, 4 and 5 (d) 1, 2, 3 and 5 

Description :

A dynamometer type wattmeter with its voltage coil connected across the load side of instrument reads 250 W. If the load voltage be 200 V, what power is being taken by load? The voltage coil has resistance of 2000 Ω. (1) 200 W (2) 215W (3) 230 W /(4) 245 W

Description :

 Moving coil in dynamometer wattmeter connected : - a) in series with fixed coil b) across supply c) in series with load d) across load

Answer :

Moving coil in dynamometer wattmeter connected : - across supply

Description :

Two wattmeter method can be used in a three phase system excited with balanced three phase supply  A) To measure real power and power factor in a balanced load B) To measure reactive power in a balanced load C) To measure real power in an unbalanced load D) All of the above 

Description :

Consider the following statements with regard to induction type wattmeter :  1. Can be used on both ac and dc systems.  2. Power consumption is relatively low.  3. It is accurate only at stated frequency and temperature.  Which of the above statements is/are correct ?  (a) 1 only (b) 2 only (c) 3 only (d) 1, 2 and 3

Answer :

Consider the following statements with regard to induction type wattmeter :  1. Can be used on both ac and dc systems.  2. Power consumption is relatively low.  3. It is accurate only at stated frequency and temperature. ... correct ?  (a) 1 only (b) 2 only (c) 3 only (d) 1, 2 and 3

Description :

Answer :

A moving iron instrument can be used for both D.C. and A.C.

Description :

Which of the following instruments can be used for measurement of very high value resistances such as insulation resistance in industries? A) Wheatstone bridge B) Megger C) Ohm-meter D) Resistive potentiometer 

Answer :

Which of the following instruments can be used for measurement of very high value resistances such as insulation resistance in industries? A) Wheatstone bridge B) Megger C) Ohm-meter D) Resistive potentiometer 

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Answer :

Murray loop test can be used for location of both the ground fault and the short-circuit fault.

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Answer :

Wattmeter cannot be designed on the principle of moving iron instrument.

Description :

A compensated wattmeter has its reading corrected for error due to (a) Frequency (b) Friction (c) Power consumed in current coil (d) Power consumed in pressure coil

Description :

For power measurement of three phase circuit by two wattmeter method, when the value of power factor is less than 0.5 lagging:

Answer :

For power measurement of three phase circuit by two wattmeter method, when the value of power factor is less than 0.5 lagging: One of the wattmeter connections will have to be reversed

Description :

A VTVM can be used to measure (a) dc voltage only (b) ac voltage only (c) both (a) and (b) (d) None of the above 

Answer :

A VTVM can be used to measure DC voltage only. If we want to measure AC voltage then we have to add rectifier.

Description :

Which of the following can be used to measure the capacitance of a capacitor? A) Rheostat B) Schering bridge C) Wheatstone bridge D) None of these

Answer :

Which of the following can be used to measure the capacitance of a capacitor? A) Rheostat B) Schering bridge C) Wheatstone bridge D) None of these

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Answer :

A PMMC instrument can be used as a fluxmeter by: Removing the control spring

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Answer :

A moving-coil permanent-magnet instrument can be used as flux-meter by eliminating the control springs.

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Answer :

A moving-coil permanent-magnet instrument can be used as ammeter by using a low resistance shunt.

Description :

Which of the following instruments can be used to measure AC current only? (a) Permanent Magnet Type ammeter(b) Induction type ammeter (c) Moving iron voltmeter(d) Moving iron ammeter

Answer :

(b) Induction type ammeter

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Answer :

The electrostatic instruments can be used without serious loss of accuracy upto 100kHz frequency.

Description :

 In a household single phase induction type wattmeter, the meter can be reversed by: - a) reversing the supply terminals b) reversing the load terminal c) opening the meter connection and reversing either the potential coil terminals or current coil terminals d) opening the meter and reversing the connection of both the potential coil terminals and current coil terminals

Answer :

 In a household single phase induction type wattmeter, the meter can be reversed by: - opening the meter connection and reversing either the potential coil terminals or current coil terminals 

Description :

The power delivered to a three-phase load can be measured by the use of 2 wattmeter only when the A. Load is balanced B. 3 -phase load is connected to the source through 3 wires C. Load is unbalanced D. 3 -phase load is connected to the source through 4 wires

Answer :

The power delivered to a three-phase load can be measured by the use of 2 wattmeter only when the  Load is unbalanced

Description :

An induction type energy meter is found to run fast. Correction for this error can be made by  (A) Over-load compensation. (B) Voltage compensation. (C) Moving the brake magnet away from the centre of the disc. (D) Moving the brake magnet towards the centre of the disc.

Answer :

An induction type energy meter is found to run fast. Correction for this error can be made by Moving the brake magnet away from the centre of the disc.

Description :

 In the measurement of power of balanced load by two wattmeter method in a 3-phase circuit, The readings of the wattmeters are 4 kW and 2 kW respectively, the later is being taken after reversing the connections of current coil. the power factor and reactive power of the load is A) 0.2 & 6 kVAR B) 0.2 & 6 √3 kVAR C) 0.32 & 2 kVAR D) 0.32 & 2 √3 kVAR

Answer :

 In the measurement of power of balanced load by two wattmeter method in a 3-phase circuit, The readings of the wattmeters are 4 kW and 2 kW respectively, the later is being taken after reversing the ... of current coil. the power factor and reactive power of the load is 0.2 & 6 √3 kVAR

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