Electrodynamometer Wattmeter consists of two coils, pressure coil (PC) and current coil (CC). Pressure coil is connected across the circuit. ELECTRODYNAMOMETER. WATTMETER’S. • These instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters. Before we study the internal construction of electrodynamometer wattmeter, it very essential to know the principle of working of electrodynamometer type.

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Electrodynamometed controlled system cannot be employed because they will appreciable amount of errors. So in order to limit the current we have connect the high value resistor in series with elecgrodynamometer moving coil. Your email address will not be published. Errors may be due connections. Assuming the electrical resistance of the pressure coil be very high hence we can neglect reactance with wattmetsr to its resistance. It consists of following parts.

We 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.

The pointer is fixed on the moving coil which is placed between the fixed coils. The above expression gives the instantaneous deflecting torque of electrodynamometer wattmeter. Due to this current proportional to supply voltage flows through the moving coil. Electromagnetic or Eddy current damping cannot be used in electrodynamometer wattmeter as it will distort the weak operating magnetic flux.

The real power divided by the apparent volt-amperes VA is the power factor. So in order to limit the electric current we have connect the high value resistor in series with the moving coil. But the instrument will respond to the average deflecting torque over a time period. The deflection of the pointer is directly proportional to the power flows through it. A modern digital wattmeter samples the voltage and current thousands of times a second.

Hence moving coil is connected across the voltage and thus the current flowing through this coil is always proportional to the voltage.

## Electrodynamometer Type Wattmeter

Electrodynamometer Type Wattmeter in general, a watt meter is used to measure the wattmster power of a circuit, or sometime it also measures the rate of energy transferred from one circuit to another circuit. In order to derive these expressions let us consider the circuit diagram given below:. In order to derive these expressions let us consider the electrdoynamometer diagram given below: Hence moving coil is connected across the voltage and thus the current flowing through this coil is always proportional to the voltage.

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Air friction damping is used, as eddy current damping will distort the weak operating magnetic field and thus it may leads to error. So the expression for the torque can be written as: Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate the measurement.

This mechanical force deflects the pointer which is mounted on the calibrated scale. There is uniform scale is used in these types of instrument as moving coil moves linearly over a range of 40 degrees to 50 degrees on either sides. The voltage across the pressure coil of the circuit is given as. The resistor controls the current across the moving coil, and it is connected in series with it.

The value of the current in the pressure coil is very small. Gravity control 2 Spring control, only spring controlled systems are used in these types of wattmeter.

### Electrodynamometer Type Wattmeter Construction and Working Principle

The two circuits of a wattmeter can be damaged by excessive current. Notify me when new comments electrodynamomeher added. Circuit Globe All about Electrical and Electronics.

The working principle of the Electrodynamometer Wattmeter is very simple and easy. The current coils are connected in series with the circuit, while the potential coil is connected in parallel.

This type of watt meter consists of two types of coil, more specifically current coil and voltage coil. Diode detectors are either directly connected to the source, or used with a sampling system that diverts only a portion of the RF power through the detector. A current flowing through the current coil generates an electromagnetic field around the coil. In electrodynamometer type wattmeter, moving coil works as pressure coil. Now let us look at constructional details of Electrodynamometer Type Wattmeter.

## Electrodynamometer Wattmeter

It uses for measuring the power of both the AC and DC circuits. These coils are called the electric current coils of electrodynamometer type wattmeter. The moving system comprises a light aluminium vane which move in a sector shaped box. Let I 1 and I 2 be the instantaneous values of currents in pressure and current coils respectively.

This article needs additional citations for verification. Now the reason is very obvious of using two fixed coils instead of one, so that it can be constructed to elsctrodynamometer considerable amount of electric current. Now let us look at constructional details of electrodynamometer. Instantaneous deflecting torque in electrodynamometer instrument is given as.