### ELECTRODYNAMIC TYPE WATTMETER PDF

The wattmeter is an instrument for measuring the electric power in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements. Contents. 1 Electrodynamic; 2 Electronic. Dynamometer Type Wattmeter Principle: If two coils are connected such Hence an electrodynamic instrument, when connected as shown in. In electrodynamometer type wattmeter, moving coil works as pressure coil. We know that instantaneous torque in electrodynamic type instruments is directly.

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The resistor controls the current across the moving coil, and it is connected in series with it.

The device consists of a pair of fixed coilsknown as current coilsand a movable coil known as the potential coil. In this the impedance is equal to its electrical resistance therefore it is purely resistive. 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. For high-power measurements, a elrctrodynamic directly measures heat produced by Electrodynamiic power.

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## Dynamometer Type Wattmeter Working

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. A typical wattmeter in educational labs has two voltage coils pressure coils and a current coil. The magnetic field in which the lightweight moving coil is situated is generated by passing current through the fixed field coils.

The value of the current in the pressure coil is very small. Scale is uniform upto a certain limit. Circuit Globe All about Electrical and Electronics. If the pressure coil is purely resistive, then their current is in phase with the voltage. These are basically moving coil instruments. This page was last edited on 27 Novemberat In this the impedance is equal to its electrical resistance therefore it is purely resistive.

Generally, a high resistance is connected in series with the moving coil to limit eectrodynamic current through it. Advantages of Electrodynamometer Type Wattmeter Following are the advantages of electrodynamometer type wattmeter and they are written as follows: The scale of the wattmeter is illustrated in figure 2 in typw upper scale is calibrated in milli-watts while the lower one measures the power in watts range.

So the expression for the torque can be written as: The supply voltage applies to the moving coil. Consequently, current I v through the moving coil is directly proportional to the load voltage.

Following are the advantages of electrodynamometer type wattmeters and they are written as follows: 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 wattmdter its resistance. Please help improve this article by adding citations to reliable sources. Ahmed Faizan Sheikh, M. The lowest measurable current is given as 0. The controlling torque exerted on the spring is given by.

### Wattmeter – Wikipedia

December Learn how and when to remove this template message. The two circuits of a wattmeter can be damaged by excessive current. 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. Electronic wattmeters are used for direct, small power measurements or for power measurements at frequencies beyond the range of electrodynamometer-type instruments. A dynamometer type wattmeter essentially consists of two coils called fixed coil and moving coil.

## Electrodynamometer Wattmeter

Dynamometer type wattmeter works on very simple principle and this principle can be stated as when any current carrying conductor is placed inside a magnetic fieldit experiences a mechanical force and due to this mechanical force deflection of electrodynamiv takes place. The current and voltage of the fixed and moving coil generate the two magnetic fields.

The moving coil of the instrument has a series resistor and is connected in parallel with electrodynamjc load.