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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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. Errors may be due to mutual inductance effects.
Electrical and electronic measuring equipment. 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. Advantages of Electrodynamometer Type Wattmeter Following are the advantages of electrodynamometer type wattmeters and they are written as follows: Leave a Reply Cancel reply Your email address will not be published.
Thus, a circuit with a low power factor will give a low reading on the wattmeter, even when both of its circuits are loaded to the maximum safety limit. Errors in Electrodynamometer Type Wattmeter Following are the errors in the electrodynamometer type wattmeters: For each sample, the voltage is multiplied by the current at the same instant; the average over at least one cycle is the real power.
As current through the pressure coil in very very small compare to current through current coil hence current through the current coil can be considered as equal to total load current.
Single phase Energy meter. Moving coil is connected across the supply voltage. Therefore this fixed coil is often called Current Coil or simply CC. The average deflection torque of the coil is given as.
Moving coil is called Pressure Coil or simply PC. Fixed Coil The fixed coil is divided into two equal parts and these are connected in series with the load, therefore the load current will flow through these coils. Where, x is the angle. These coils are called the current coils of electrodynamometer type wattmeter. 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.
Moving coil is also called Pressure Coil or PC. These types of instruments are only used for measuring the dc quantities as if we wwattmeter ac current to these type of instruments the […].
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. In fact, a watt meter is a package of an ammeter and a voltmeter, because the product of voltage and current is the power, which is the measurable quantity of a watt meter When current flows through the current coils, then automatically a magnetic field is developed around those coils.
The deflection of the pointer is directly proportional to the power flows through it. Errors in the pressure coil inductance. The voltage limit of moving coil is limited to about V by the power requirement of voltage circuit since most of electfodynamometer power is dissipated in the series resistor of voltage circuit.
Gravity controlled system cannot be employed because they will appreciable amount of errors. Now let us derive the expressions for eleectrodynamometer controlling torque and deflecting torques. Let the rms voltage of circuit is V and current flowing is I.
The moving is air cored and is mounted on a pivoted spindle and can move freely. The two pressure coils can be connected in series or parallel to change the ranges of the wattmeter. Earlier these fixed coils are designed to carry the current of electroodynamometer amperes but now the modern wattmeter are designed to carry current of about 20 amperes in order to save power. As a high value of series resistance is connected in series with the PC, therefore PC circuit electrodynqmometer be assumed purely resistive.
Thermistors and thermocouples are used to measure heat produced by RF power and can be calibrated either directly or by comparison with wattmeer known reference source of power.
The value of the current in the pressure coil is very small.
A typical wattmeter in educational labs has two voltage coils pressure coils and a current coil. In other projects Wikimedia Commons. 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.
These coils are called the current coils of electrodynamometer type wattmeter. In earlier design of Electrodynamometer wattmeter the fixed coil were designed to carry current of the order of A.
The two circuits of a wattmeter can be damaged by excessive current. The sensor element is maintained at a constant temperature by a small direct current. Now let us derive the expressions for the controlling torque and deflecting torques.
Notify me when new comments are added. Posted on June 1, July 24, Author Mr. Following are the wlectrodynamometer of electrodynamometer type wattmeters and they are written as follows: 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.
Let I 1 and Electrodynajometer 2 be the instantaneous values of currents in pressure and current coils respectively.
Electrodynamometer Type Wattmeter Construction and Working Principle
Leave a Reply Cancel reply Your email address will not be published. Learn how your comment data is processed. There is uniform scale is used in these types of instrument as moving coil moves linearly over a watgmeter of 40 degrees to 50 degrees on either sides.
Therefore, a wattmeter is rated not only in watts, but also in volts and amperes. Now let us look at constructional details of Electrodynamometer Type Wattmeter. There are two current coils which are kept at constant wattmerer and the measurable current will flow through those current coils.