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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Due to moment of inertia of moving system, the pointer will not follow rapidly changing alternating torque and will fail to show any reading. In electrodynamometer type wattmetermoving coil works as pressure coil.

Electrodynamometer i nstruments are capable of serving as transfer instruments. It shows that the deflecting torque is proportional to the product of currents flowing in the fixed and the moving coil.

This site uses Akismet to reduce spam. These springs act as leads to the moving coil. Let the currents passing through fixed and moving coils be I 1 and I 2 respectively. When current passes through the fixed and moving coils, both coils produce the magnetic fields.

Electrodynamometer type Instruments – Construction and Operation. The construction of moving coil is made light as well as rigid. Grab it now for very less price.

As the electrdynamometer through the moving coil shall not exceed mA, therefore moving coil is shunted by suitable resistance to increase the range of such ammeter. They can be used for both to measure ac as well dc quantities as scale is calibrated for both.


Electrodynamometer Wattmeter

Let us assume an infinitesimally small time dt for the sake of calculation of change in stored energy. Leave a Reply Cancel reply Your email address will not be published. Hence the instrument is often used as instrumfnts calibration instrument. This makes the system heavy reducing torque to weight ratio. Iinstruments Instruments are widely used as an ammeter, voltmeter and wattmeter. Since the direction of current is changing in each half cycle, there will be a corresponding change in the direction of magnetic flux.

Electrodynamometer Type Wattmeter

It consists of counter weights and pointer. The rype field required for the operation of the instrument is produced by the fixed coils. Instead of a permanent magnet, the electrodynamometer type instrument uses the current under measurement to produce the necessary field flux.

Therefore we can write as. It is recommended to read before going to understand the torque equation. A transfer instrument is one which is calibrated with a d.

Electrodynamometer Type Wattmeter

Moving coil is serves the purpose of converting the actuating quantity into readable value on the scale. Hnec metal parts should be kept as minimum instrumfnts possible.

The fixed coil connects in series with the circuit whose power consumption use to be measured. Change in stored energy.

Pabitha Pabi June 28, at 5: Gravity control Spring control, only spring controlled systems are used in these types of wattmeter. Thus the deflection is proportional to the product of the two currents and the rate of change of mutual inductance.


A suitable shunt is connected to these coils to limit current through them upto desired limit. Spring provides the controlling torque. A uniform field is obtained near the center of coil electrodynamoketer to division of coil in two sections.

But moving system, due to inertia cannot follow rapid variations and thus finally meter shows the average torque. 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 tpye. The supply voltage applies to the moving coil.

Torque Equation in Electrodynamometer Instruments | Electrical Concepts

As operating field would be distorted by eddy current damping, it is not employed. A transfer instrument is one that may be calibrated with a d. Obviously, your answer will be there will be no deflection in the needle of PMMC instrument. The average deflection torque is obtained by integrating the torque from 0 to T limit. The instantaneous torque acts on the pointer of the wattmeter and is given by the equation.

So shielding is done to protect it from stray magnetic fields. The wattmeter indicates the supply power. All Categories appendix Basic basics of transmission and distribution Batteries C.