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Induction type wattmeter provides accurate readings only when:

Induction type wattmeter provides accurate readings only when: Correct Answer both frequency and supply voltage are constant

Induction type wattmeter provides accurate readings only when both frequency and supply voltage are constant.

Concept:

 

Induction-type instruments have the following advantages and disadvantages.

Advantages:

  • A full-scale deflection of over 300° can be obtained giving a long open scale.
  • Damping is good.
  • The effect of stray magnetic fields on the readings is small as the operating forces are large.

 

Disadvantages:

  • Power consumption is fairly high in these instruments
  • The cost of the instrument is high
  • The large deflection produces large stresses in the springs
  • Serious errors are caused due to changes in frequency and temperature unless properly compensated. Therefore, these instruments are useful only for switch-boards where there is not much variation in frequency.
  • The instruments are only suitable for ac
  • The scale is non-uniform 

Additional Information

Various Measuring Parameter: 

Meter Parameter Instrument used
Ammeter Current PMMC, EMMC,
MI, Hot Wire
Voltmeter Voltage PMMC, EMMC,
MI, Hot Wire,
Electrostatics Type
Power Factor Meter Power Factor Dynamometer Type,
Moving Iron type
Watt-hour Meter
(Energy Meter)		 Energy Induction Type
Wattmeter Power Dynamometer Type,
Induction Type
Frequency Meter Frequency Moving iron type,
Dynamometer Type,
Vibrating Type

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