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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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. Following are the advantages of electrodynamometer type wattmeters and they sattmeter written as follows:. Scale is uniform up to certain limit b. The value of the current in the pressure coil is very small.
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 wzttmeter. Posted on June 1, July 24, Author Mr. Where, x is the angle. Following are electrodynamometeer advantages of electrodynamometer type wattmeters and they are written as follows: 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.
Due to this the sizes of earlier wattmeter were large.
A limited amount of current flows through the moving coil so as to avoid heating. Errors may be due to pressure coil capacitance.
Electrodynamometer Wattmeter – Construction | Electrical Concepts
And the value of current is given by the equation. Working Principle of Electrodynamometer Qattmeter. Therefore controlling torque Tc is given as. A modern digital wattmeter samples the voltage and current thousands of times a second.
Diode detectors are either directly wattmteer to the source, or used with a sampling system that diverts only a portion of the RF power through the detector. In this the impedance is equal to its electrical resistance therefore it is purely resistive.
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. Now let us look at constructional details of electrodynamometer. And the interaction of these two magnetic fields deflects the pointer of the instrument. Pressure coil is connected across the circuit whose power is to be measured and current coil is connected in series. Now let the applied value of voltage across the pressure coil be Assuming the electrical resistance to the pressure coil be very high hence we can neglect reactance with respect to its resistance.
A voltage coil is placed inside those two current coils, and this voltage coil is totally free to rotate. This article needs additional citations for verification. This mechanical force deflects the pointer which is mounted on the calibrated scale.
In electrodynamometer type wattmetermoving coil works as pressure coil. This page was electrodynamomeger edited on 27 Novemberat Let the rms voltage of circuit is V and current flowing is I. Errors electrodunamometer by vibration of moving system.
This site uses Akismet to reduce spam. Air friction damping is used, as eddy current damping will distort the weak operating magnetic field and thus it may leads to error. Now let us derive the expressions for the controlling torque and deflecting torques.
Construction and Working Principle of Electrodynamometer Type Wattmeter Now let us look at constructional details of electrodynamometer. In this wattmeter impedance is equal to its electrical resistance therefore it is purely resistive. It uses for measuring the power of both the AC and DC circuits.
Learn how your comment data is processed. Electromagnetic or Eddy current damping cannot be used in electrodynamometer wattmeter as it will distort the weak operating magnetic flux.
Electrodynamometer Type Wattmeter
They can be used for both to measure ac as well dc quantities as scale is calibrated for both. Moving coil moves the pointer with the help of spring control instrument.
Electtrodynamometer there is phase difference between voltage and electric current, then expression for instantaneous current through current coil can be written as As current through the pressure coil is very very small compared to the current through current coil hence current through the current coil can be considered as equal to total load current. Hence moving coil is connected across the voltage and thus the current electrodynamometeer through this coil is always proportional to the voltage.
Hence moving coil is connected across the voltage and thus the electric current flowing through this coil is always proportional to the voltage.
In electrodynamometer type wattmetermoving coil works as pressure coil.