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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Errors may be due to mutual inductance effects. Electrical and electronic measuring equipment. Electrical Instruments and Classification of instruments. The pressure coil can also be tapped to change the meter’s range. This particularly affects low power e. Instantaneous deflecting torque in electrodynamometer instrument is given as.
There are two types of coils present in the electrodynamometer. In electrodynamometer type wattmetermoving eectrodynamometer works as pressure coil. Wattmeters vary considerably in correctly calculating energy consumption, especially when real power is much lower than VA highly reactive loads, e.
Air friction damping is used, electrodynnamometer eddy current damping will distort the weak operating magnetic field and thus it may leads to error. These types of instruments are only used for measuring the dc quantities as if we apply ac current to these type of instruments the […]. December Learn how and when to remove this template message.
Therefore this fixed coil is often called Current Coil or simply CC.
This mechanical force deflects the pointer which is mounted on the calibrated scale. Waveforms for switched-mode power supplies as used for much electronic equipment may be very far from sinusoidal, leading to unknown and possibly large errors wwattmeter any power. Therefore for higher voltage Potential Transformer shall be used. The device consists of a pair of fixed coilsknown as current coilsand a movable coil known as the potential coil.
Errors in Electrodynamometer Type Wattmeter Following are the errors in the electrodynamometer type wattmeters: Fixed coil or CC is carries the circuit current. Hence the current flows through the pressure coil is considered as the total load current.
Working Principle of Electrodynamometer Wattmeter | Electrical Concepts
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. Before we study the internal construction of electrodynamometer wattmeterit very essential to know the principle of working of electrodynamometer type wattmeter. Moving coil moves the pointer with the help of spring control instrument.
Moving coil is connected across the supply voltage. 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. When current flows through the current coils, then automatically a magnetic field is developed around those coils.
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. The wire is either stranded or laminated to avoid eddy current loss.
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 typical wattmeter in educational labs has two voltage coils pressure coils and a current coil.
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. Connects Facebook Youtube Videos. Hence moving coil is connected across the voltage and thus the current flowing through this coil is always proportional to the voltage. And the voltage coil is connected in parallel with the circuit. Moving Iron instruments Principle and operation.
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 electrodynamoneter flux linked with the circuit. Gravity controlled system cannot be employed because there will be appreciable amount of errors. Their working depends on the theory that the current carrying conductor placed in a magnetic field wattmeer a mechanical force.
Electronic wattmeters are used for direct, small power measurements or for power measurements at frequencies beyond the range of electrodynamometer-type instruments. The deflection of the pointer is directly proportional to the power flows through it.
A limited amount of current flows through the moving coil so as to avoid heating. Gravity controlled system cannot be employed because they will appreciable amount of errors. Scale is uniform upto a certain limit. 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.
Wattmeter – Wikipedia
So the expression for the torque can be written as: We know that instantaneous torque in electro dynamic type instruments is directly proportional to product of instantaneous values of currents flowing through both the coils and the rate of change of flux linked with the circuit. Moving coil moves the pointer with the help of spring control instrument. Following are the advantages of electrodynamometer type wattmeters and they are written as follows: Learn how your comment data is processed.
Therefore controlling torque Tc is given as.
Advantages of Electrodynamometer Type Wattmeter Following are the advantages of electrodynamometer type wattmeter and eleectrodynamometer are written as follows: Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate the measurement. 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.
So in order to limit the current we have connected the high value resistor in series with the moving coil. Unsourced material may be challenged and removed.