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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If a pointer is connected with the moving coil, which will move of a scale, then the deflection can be easily measured by connecting the moving coil with that pointer. So the expression for the torque can be written as:. December Learn how and when to remove this template message. Errors in the pressure coil inductance. Earlier these fixed coils are designed to carry the current of about amperes but now the modern wattmeter are designed to carry current of about 20 amperes in order to save power.

Now let us derive the wattmetsr for the controlling torque and deflecting torques. Due to this power dissipation in series resistor of PC, heat is generated. 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. Gravity controlled system cannot be employed because they will appreciable amount of errors. An electrodynamometer wattmeter have two types of coils.

The deflection of the pointer is directly proportional to the power flows through it. Moving coil is connected across the supply voltage. In this the impedance is equal to its electrical resistance therefore it is purely resistive.

In order to derive these expressions let us consider the circuit diagram given below: As discussed earlier in the post, a series resistor is used in PC to limit the current upto mA. As simple as other voltmeter and ammeter connection. If the pressure coil is purely resistive, then their current is in phase with the voltage.

Controlling torque is provided by spring. Circuit Globe All about Electrical and Electronics. And the value of current is given by the equation.

### Wattmeter – Wikipedia

In this the impedance is equal to its electrical resistance therefore it is purely resistive. Scale is uniform upto a certain limit. Therefore this fixed coil is often called Current Coil or simply CC. Moving coil is called Pressure Coil or simply PC. Electrical and electronic measuring equipment. In practice accuracy can be improved by connecting a fixed load such as an incandescent light bulb, adding the device in standby, and using the difference in power consumption.

Wattmeters vary considerably in correctly calculating energy consumption, especially when real power is much lower than VA highly reactive loads, e. It consists of following parts There are two types of coils present in the electrodynamometer. Limited of current flows through the moving coil so as to avoid heating.

## Electrodynamometer Type Wattmeter

The voltage across the pressure coil of the circuit is given as. Scale There is uniform scale which is used in these types of instrument as moving coil moves linearly over a range of 40 degrees to 50 degrees on either side. The readings may be displayed on the device, electrodynamometsr to provide a log and calculate averages, or transmitted to other equipment for further use.

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Before we study the internal construction of electrodynamometer wattmeter electrrodynamometer, it very essential to know the principle of working of electrodynamometer type wattmeter. In order to derive these expressions let us consider the circuit diagram given below:. Therefore they can easily carry heavier current. In order to derive these expressions let us consider the circuit diagram given below:.

This type of watt meter consists of two types of coil, more specifically current coil and voltage coil.

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