An electrodynamometer is an instrument used for measuring the electric power. The basic principle was laid out in an paper by Wilhelm Weber. 5 Nov An electrodynamic type instrument consists of Two Fixed Coil, flux is used in Electrodynamic or Electrodynamometer type instrument. 5 Nov This means that the torque in electrodynamometer instruments must have . Electrodynamometer type voltmeters are the most accurate type of.

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Let I 1 and I 2 be the current in fixed and moving coil insturments. The magnetic filed in electrodynamic type instrument is very week of the order of 0.

Thus as it is a transfer instrument, there is direct connection between a.

The pointer comes to rest at a position where deflecting torque is equal to the controlling torque. The rotating coil consists of many turns of fine wire, and is connected across the load with a multiplier resistance in series with it to measure the potential drop.

Errors may be due to pressure coil capacitance. The moving coil is attached to the moving system so that under the action of deflecting torque, the pointer moves over the scale. Thus ytpe deflection typw decided by the product of r.


The coils are usually varnished. A transfer instrument is one which is calibrated with a d.

The electrodynamometer type instruments are often used in accurate a. Therefore it becomes very important to protect the instrument from the effect of external magnetic field. Besides, their use as an ammeter, voltmeter, and wattmeter; they are also used to transfer calibration of working instruments.


This means that the torque in electrodynamometer instruments must have a finite value and unidirectional for AC and DC quantity unlike PMMC instruments. Errors in the pressure coil inductance. As operating field would be distorted by eddy current damping, it is not employed. The moving is instuments cored and is mounted on a pivoted spindle and can move freely.

Similar to moving iron instruments the operating field in electrodynamometer instrument is very weak. Controlling torque is provided by two control springs.

Electrodynamometer type Instruments – Construction and Operation

The wattmeter indicates the supply power. The field produced by these instruments is very weak. This site uses Akismet to reduce spam. An electrodynamometer is an instrument used for measuring the electric power.

Thus we can write. Connects Facebook Youtube Videos. These instruments are based on that principle the mechanical force exists between the current carrying conductors. Thus the instrumwnts on the moving coil will not change rather it will be unidirectional. In the Siemens instrument, the stationary coil is made of relatively few turns of heavy wire and is connected in series with the circuit. It is clear that deflection of the pointer is directly proportional to the square of the operating current.


Posted by pragna chukka at Let us see its operation on a. The changes in the frequency causes to change self inductances of moving coil and fixed coil. The instrument consists of a fixed coil and a moving coil. In electrodynamometer type wattmetermoving coil works as pressure coil.

Electrodynamometer Type Wattmeter

Now the reason is very obvious of using two fixed coils instead of one, so that it can be constructed to carry considerable amount of electric current. Change in stored energy. Elecrodynamometer know that instantaneous torque in electrodynamic type instruments is directly proportional to the product of instantaneous values of currents flowing through both the coils and the rate of change of flux linked with the circuit.

Some of the above input energy to electrodynamometer instruments are stored in the form of magnetic energy in the coil while rest is converted into mechanical energy of moving coil. Learn how your comment data is processed. In metal parts of the instrument the eddy current gets produced. It would have a torque in one direction during one half of the cycle and an equal effect in the opposite direction during the electrorynamometer half of the cycle.

In the figure above, voltmeter is connected between points A and B to measure the voltage drop across it.