The instrument that measures the low value of power factor accurately is known as the Low Power Factor Wattmeter (LPFW). The low power factor meter is used. So LPF(Low Power Factor) Wattmeter is used in OPEN CIRCUIT TEST of Transformer. In short circuit test the secondary winding of transformer. LPF wattmeter is used for measuring power in highly inductive circuits & UPF wattmeter is used for measure power in resistance circuit in which the power factor.

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Still looking for expert help? Now let us derive an expression for the correction factor for pressure coil inductance. Year of Establishment Thus in this case we have power shown by the first wattmeter is equal to the power loss in the load plus power loss in the current coil.

Above two reasons gives very inaccurate results thus we should not use normal or ordinary watt meters in measuring the low value of power factor.

Inventor of the wattmeter? Get 5 credit points for each correct answer.

What is Low Power Factor Wattmeter? – Definition & Explanation – Circuit Globe

Here we are going to discuss, where we need to do modification. I agree to the terms and privacy policy. Nature of Business Manufacturer. Find more suppliers in Chennai Wattmeter in Chennai.

Leave a Reply Cancel reply Your email address will not be published. The capacitor eliminates the error. Thereby, the wattmeetr of the pressure coil voltage is not equal to the supplied voltage. Your email address will not be published.

What is Low Power Factor Wattmeter?

How does a wattmeter work? There is a requirement of low power factor meter because, the usage of ordinary electrodynamometer wattmeter to measure power factor of a low pf load gives inaccurate results. The total power measured by the pressure coil is equal to the sum of the power loss in the load and the power loss in the current coil. The supply voltage is equal to the voltage across the pressure coil. If, by ‘upf’, you mean wattmdter power factor’, then all wattmeters measure the in-phase component of wattmetef load current, so the term is quiet unnecessary.


What is analog wattmeter?

The compensating coil is connected in series with the pressure coil circuit and is made nearly identical to the current coil. A short-circuit te … st is used to determine the true power loss in the transformer, which is exactly what a wattmeter measures. The compensating coil compensates the error in the circuit which induces because of low power factor.

Answers and Solutions

Circuit Globe All about Electrical and Electronics. This current produces the deflecting torque on the moving coil. The voltage across pressure coil is equal to the voltage across the load.

Subscribe to our mailing list and get interesting stuff and updates to your email inbox. Inductive circuits have the property of lagging power factor and hence these wattmeters are used.

Thus in order to avoid this situation we have connect the variable series resistance with a capacitor as shown in the above figure. It is similar to the SPF number on sunscreens, but it is used for clothing. In the first category both the ends of the pressure coil is connected to supply side i. HPF is high p … ass LTI filter which passes the high frequencies and reduce the amplitude of the frequencies lower than filter’s cutoff frequency.


The modified circuit is shown below: The pressure coil is designed for having a low value of resistance so that the high value of current passes through it.

If we consider the inductance of pressure coil we don’t have voltage across pressure in phase with the applied voltage. In figure lpc the pressure coil is parallel connected to the supply voltage.

What is ac wattmeter? And the current coil is connected in series with the kpf voltage. The rotation of the rotor causes the display dials to count up at certain values per rotation. The compensating coil is so connected that it opposes the field of the current coil. Your email address will not be published.

Acknowledged for their dimensional accuracy, light weight and compact design, our products are widely used for various applications in the field of basic electronics, power electronics, analogue communication, digital communication and wathmeter other areas.

In this category two cases diagrams arises and these are shown below: Answers and Solutions What’s Your Question? Owing to our quality approaches and transparent business dealings, we have acquired a huge lpff all over the country. This final modified circuit so obtained is called wattmetre power factor meter.

The ordinary Wattmeter used for measuring the low power factor gives the inaccurate result. In the second category, the current coil is not in series with the load and the voltage across the pressure coil is not equal to the applied voltage.