Applications of Electrodynamometer Type Instruments

Electrodynamometer type instruments can be used as ac voltmeter, Ammeters, Wattmeters and p.f. meters. With slight modification, they can also work as analogue frequency metres.

1. Electrodynamometer Type Ammeter

Below figure shows the arrangement of coils of an electrodynamometer ammeter. Two arrangements are shown. One is used for current below 100 mA and the other for current above 100 mA.

2. Electrodynamometer Type Voltmeter

An electrodynamometer type movement is used as a voltmeter by connecting the fixed and the moving coils in series with a high non-inductive resistance. The connection diagram is shown below in figure.

Note: 

The voltmeter of electrodynamometer type instruments read rms value of the voltage because deflection, θ is directly proportional to square of the input voltage.

3. Electrodynamometer Type Wattmeter

Below figure shows the construction of electrodynamometer type wattmeter

Thus, deflection is proportional to power measured by wattmeter.

4. Electrodynamometer Type Power Factor Meter

Below figure shows an electrodynamometer instrument arrangement to measure power factor of the load.
It consists of two fixed coils and two moving coils.

Electrodynamometer, type power factor meter has inherent controlling torque at equilibrium, and do not
require any spring.

5. Electrodyanometer Type Frequency Meter

Below figure shows the arrangement of frequency meter.

 

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