Why compensating winding is used in wattmeter?
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Why compensating winding is used in wattmeter?
In a low power circuit, the value of the current is high, and that of the power is low. This high-value current causes the error in the wattmeter reading. To reduce this error, the compensation coil is used in the circuit.
What is a compensated wattmeter has its reading?
Answer: A compensated wattmeter has its reading corrected for error due to power consumed in potential coil.
How do you compensate pressure coil in wattmeter?
- To compensate for the power loss in the pressure coil,compensating coil with an equal number of turns of the current coil is connected in series opposition to the potential coil or pressure coil.
- Compensating coil requires only for LC connection not for MC connection.
Why do we use compensating coil in wattmeters designed for low power factor measurements?
Compensation coil in LPF wattmeter: In case the load current is large and the power factor is small, the error caused by the pressure coil in the L-C short wattmeter is large. Hence, in wattmeter is designed for low power factor measurements.
What is the purpose of compensating windings?
A compensation winding in a DC shunt motor is a winding in the field pole face plate that carries armature current to reduce stator field distortion. Its purpose is to reduce brush arcing and erosion in DC motors that are operated with weak fields, variable heavy loads or reversing operation such as steel-mill motors.
What is meant by compensating winding?
Definition of compensating winding : a winding embedded in the pole faces of a commutating alternating-current or direct-current machine and connected in series with the armature, the magnetic field of the winding neutralizing the cross-magnetizing field of the armature.
What value of wattage is measured by a dynamometer type wattmeter?
Explanation: Dynamometer type wattmeter is used for the measurement of A.C. as well as D.C. power.
How is the compensation for inductance of pressure coil realized on low power factor watt meter?
(c) Compensation for pressure coil inductance: At low power factor, the error caused by the pressure coil inductance is very large. Hence, this has to be compensated, by connecting a capacitor C across a portion of the series resistance in the pressure coil circuit as shown in figure 4.5.
What is UPF and LPF?
LPF wattmeter is used to measure power in inductive circuits. Inductive circuits have the property of lagging power factor and hence these wattmeters are used. Resistive circuits have unity power factor hence UPF wattmeters are used to measure power in these circuits.
What is the cause of negative reading of the wattmeter?
The reading of a wattmeter is proportional to (current thro’ the current coil)x(voltage across the pressure coil)xCosine(angle between this current and this voltage). So if this angle becomes more than 90 degrees the the reading of the wattmeter will be negative.
Where is the compensating winding located?
pole faces
Compensating winding is embedded in the slots in pole faces. It is connected in series with the armature winding so that their mmfs are proportional to the same current.
How are compensating windings connected?
The compensating windings are connected in series with each other and with the armature winding in a manner similar to the interpole windings so that they also oppose the field set up by armature reaction. The current in them is then equal to that in the armature.
Why we use compensating winding?
What is MLC in wattmeter?
The terminal M & L represents Current coil While C & V Potential coil. The M terminal connects to the power supply. ‘L’ it is used to connect load. ‘C’ it is shorted with M. ‘V’ it is a voltage to connect transformer neutral and also.
What are the errors and their compensation in dynamometer type wattmeter?
Errors in Electrodynamometer Type Wattmeter Errors may be due to pressure coil capacitance. Errors may be due to mutual inductance effects. Errors may be due connections. (i.e. pressure coil is connected after current coil)
What is the effect of capacitance on wattmeter reading?
What is the effect of capacitance on wattmeter reading? Explanation: For lagging power factor of the load, the wattmeter reading is more. As a result, the wattmeter shows a reading opposite to that of the inductance. 3.
What is Upper power factor?
What is meant by phantom loading?
Phantom load, also known as standby power or vampire power, is the electricity consumed by an electronic device while it is turned off or in standby mode. It is the power that maintains your TV settings and keeps the clock going on your VCR and microwave, but this power comes at a price.
How do you fix a negative reading on a wattmeter?
For angle, more than 60° or cosϕ < 0.5, wattmeter will give a negative reading. To take negative reading either potential coil or current coil connection should be reversed.
What are Compensating windings in DC machine?
In order to neutralize the cross magnetizing effect of armature reaction, a compensating winding is used. The compensating windings consist of a series of coils embedded in slots in the pole faces. These coils are connected in series with the armature. Compensating Windings and Interpoles in dc machine
How are Compensating windings connected in series?
The compensating windings are connected in series with each other and with the armature winding in a manner similar to the interpole windings so that they also oppose the field set up by armature reaction. The current in them is then equal to that in the armature.
What is the direction of current in compensating winding?
Half of the compensating winding in the right side pole face is connected in series with the half of the left side pole face winding as shown in above figure. In this way, the direction of current in compensating winding is opposite to that in the armature winding.
Why do Compensating windings cancel the cross magnetizing effect of armature?
Because the compensating windings are wound to produce a field that opposes the magnetic field of the armature, they tend to cancel the cross magnetizing effect of the armature magnetic field. The neutral plane will remain stationary and in its original position for all values of armature current.
