March 26, 2020


The electrodynamometer type instrument is a transfer instrument. A transfer instrument is one which is calibrated with a d.c. source and used without any. An electrodynamic type instrument consists of Two Fixed Coil, flux is used in Electrodynamic or Electrodynamometer type instrument. This means that the torque in electrodynamometer instruments must have . Electrodynamometer type voltmeters are the most accurate type of.

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Electrodynamometer Type Wattmeter

Leave a Reply Cancel reply Your email address will not be published. Thus the deflection is decided by the product of r.

Electrodynamometer i nstruments are capable of serving as transfer instruments. Construction and Working Principle of Electrodynamometer Type Wattmeter Now let us look at constructional details of electrodynamometer. If metallic former is used, then it would induce eddy currents in it. The controlling torque is provided by springs. An electrodynamometer type instrument is a moving coil instrument in which the operating field is produced by another coil which is fixed.

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Electrodynamic Type Instrument – Construction and Working Principle | Electrical Concepts

Let us see its operation on a. Sometimes a suspension may be used, in case a high accuracy is desired. If there is phase difference between voltage and electric current, then expression for instantaneous current through current coil can be written as As electfodynamometer through the pressure coil is very very small compared to the current through current coil hence current through the current coil can be considered as equal to total load current.


For understanding the working principle, first ask yourself what will happen if we connect a PMMC instrument for the measurement of AC quantity? It is generally wound on a non magnetic metallic former.

They can be used for both to measure ac as well dc quantities as scale is calibrated for both. This principle is used in the electrodynamometer type instrument. Errors may be due connections. It is done by enclosing in a casing high permeability alloy. Grab typf now for very less price. Deflecting Torque in Ammeter.

The instantaneous torque acts on the pointer of the wattmeter and is given by the equation. Chand ” is the best in industry. Thus ideally electroydnamometer needle of PMMC instrument shall swing back and forth around zero position.

Moving coils are also air-cored. Errors caused by vibration of moving system. The frequency error can be reduced by having equal time constants for both fixed and moving coil circuits. Fixed coil is provided for the sake of production of magnetic field.


This mechanical force deflects the pointer which is mounted on the calibrated scale. The supply voltage applies to the moving electrodynamomdter. Also the resistivity of the metal parts used must be high, to reduce the eddy currents. A suitable shunt is connected to these coils to limit current through them upto desired limit.

Electrodynamometer Type Wattmeter

Scale is uniform upto a certain limit. Fixed Coil The fixed coil is divided into two equal parts and these are connected in series with the load, therefore the load current will flow through these coils. This means that the torque in electrodynamometer instruments must have a finite value and unidirectional for AC and DC quantity unlike PMMC instruments.

Your email address will not be published. The instrument consists of a fixed coil and a moving coil. Suppose the torque on moving coil for positive half cycle of AC quantity is clockwise then it will change to anticlock wise direction in the negative half cycle. This site uses Akismet to reduce spam.