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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Such a transfer instrument has same accuracy for a.

Electrodynamometer Type Wattmeter

The temperature errors are caused instrumments to the self heating of the coil, which causes change in the resistance of the coil. With some little modifications, it can be used as a wattmeter for the power measurements. Now suppose, if we were able to reverse the direction of magnetic flux each time the direction of AC quantity changes through the moving coil then we can have a unidirectional torque. Therefore can must be taken while handling them. In order that the instrument should be able to read a.

Moving Coil Moving coil moves insgruments pointer with the help of spring control instrument. The current cannot be made very high because it may cause excessive instrumsnts of springs. Torque to weight ratio: Your email address will not be published.

Dynamometer type wattmeter works on very simple principle and this principle can be stated as when any current carrying conductor is placed inside a magnetic fieldit experiences a mechanical force instrumengs due to this mechanical force deflection of conductor takes place.


It uses instrjments measuring the power of both the AC and DC circuits. These springs act as leads to the moving coil.

They are clamped in place against the coil supports. The current and voltage of the fixed and moving coil generate the two magnetic fields.

Hence moving coil is connected across the voltage and thus the current flowing through this coil is always proportional to the voltage. It is air cored. This type of instrument is known as Elctrodynamometer type instrument.

Pabitha Pabi June 28, at 5: If metallic former is used, then it would induce eddy currents in it. This makes the construction rigid.

To reduce the effect of stray magnetic field, the shields must be used for the instruments. Learn how your comment data is processed. Change in stored energy. The average torque for one time period of the currents are given by. Therefore, Deflecting Torque in Ammeter. Newer Post Older Post Home. At equilibrium the controlling torque and deflecting torques are equal, hence.

To get accurate results, these errors must be minimized. To have reasonable deflecting torque, mmf of the moving coil must be large enough. It is most accurate type of voltmeter.

Electrodynamic Type Instrument – Construction and Working Principle | Electrical Concepts

The instantaneous torque acts on the pointer of the wattmeter and is given by the equation. Thus we can measure the AC quantity. Leave a Reply Cancel reply Your email address will not be published.

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Control System Out of two controlling systems i. This makes the system heavy reducing torque to weight ratio.

Related pages Measurement of Three Phase Power. The moving coils acts as a voltage coil or pressure oil and must be connected across the supply terminals.

These springs act as leads to the moving coil. For using electrodynamometer elevtrodynamometer as a wattmeter to measure the power, the fixed coils acts as a current coil and must be connected in series with the load.

An electrodynamometer electrodynamkmeter instrument is a moving coil instrument in which the operating field is produced by another coil which is fixed.

Electrodynamometer type Instruments – Construction and Operation

A uniform field is obtained near the center of coil due to division of coil in two sections. The value of the electrofynamometer in the pressure coil is very small. The magnetic filed in electrodynamic type instrument is very week of the order of 0. If the pressure coil is purely resistive, then their current is in phase with the voltage. This causes the error in the reading.

The deflection produced in the instrument is proportional to the product of currents flowing in the fixed and the moving coil. Errors in the pressure coil inductance.