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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Leave a Reply Cancel reply Your email address will not be published. Hence the current flows through the pressure coil is considered as the total load current.

A transfer instrument is one which is calibrated with a d. Even earth’s magnetic field considerably affects the instrumentd. Errors in Electrodynamometer Type Wattmeter Following are the errors in the electrodynamometer type wattmeters: Air friction damping is provided by aluminium vanes attached to the spindle at the bottom. Thus temperature compensating resistors can be used in the precise instrument to eliminate the temperature errors.

electrodyynamometer Moving coil is serves the purpose of converting the actuating quantity into readable value on the scale. They are clamped in place against the coil supports.


The necessity for the AC calibration of moving iron instruments as well as another type of instruments which cannot be correctly calibrated requires the use of a transfer type of instrument. Errors caused by vibration of moving system. We will discuss each of them one by one.

Electrodynamometer Type Instruments ~ your electrical home

This site uses Akismet to reduce spam. The value of the electroynamometer in the pressure coil is very small. Electrodynamometer i nstruments are capable of serving as transfer instruments.

And the value of current is given by the equation. A uniform field is obtained near the center of coil due to division of coil in two sections. Learn how your comment data is processed.

Electrodynamometer Wattmeter

The controlling torque exerted on the spring is given by. The PMMC instrument cannot be sued on a.

It is recommended to read before going to understand the torque equation. The scale is thus calibrated in terms of the square root of the average current squared i.

The frequency error can be reduced by having equal time constants for both fixed and moving coil circuits.

The electrical energy input to the instrument. There are two types of coils present in the electrodynamometer.

Electrodynamometer type Instruments – Construction and Operation

These coils are called the current coils of electrodynamometer type wattmeter. To get accurate results, these errors must be minimized. It can be seen that deflecting torque depends upon the multiplication of instantaneous value of current and rate of change of mutual inductance between the fixed and moving coil.


But this deflecting torque is controlled by the spring. Thus the deflection is decided by the product of r. Let us assume that the current in fixed coil be I 1 and that in moving coil be I 2 as shown in figure below.

Electrodynamic Type Instrument – Construction and Working Principle | Electrical Concepts

The electrodynamometer type instruments are often used in accurate a. Really very gud looking. Figure below shows an electrodynamometer ammeter. We have an idea of the working ttpe of e lectrodynamometer instrument instrumennts taking up a permanent magnet moving coil instrument and considering how it would behave on a.

Please keep doing this. Let us see its operation on a. The moving coils acts as a voltage coil or pressure oil and must be connected across the supply terminals.