Answer / maniveer

LOW POWER FACTOR(LPF) & HIGH POWER FACTOR(UPF)

 In open circuit test the secondary winding of transformer is kept open.As the secondary side is open, the entire coil will be purely inductive in nature.So the power will be lagging due to inductive property of the circuit. So LPF(Low Power Factor) Wattmeter is used in OPEN CIRCUIT TEST of Transformer.
          
            In short circuit test the secondary winding of transformer is short circuited. As secondary side is short circuited the entire coil will be purely resistive in nature.So the power factor will be unity. So UPF(Unit Power Factor) Wattmeter is used in SHORT CIRCUIT TEST of Transformer.

Answer / venkata krishna

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 ranges from
0.5 to unity.

Answer / potnur hemarao

Lpf is used in power measuring in high inductive circuit and upf is used in power measuring in resistance circuit which power factor ranges 0.5 to unity

Answer / nitish kennedy

Low Power Factor wattmeters are specially designed to measure power at low power factor .

Ordinary wattmeters (i.e. UPF) are not accurate in measuring power at low power factor beacuse of -

low deflecting torque.
error due to inductance of of pressure coil is large at low power factor.
So some modifications are done in LPF wattmeters-

low value of pressure coil resistance to increase the torque.
pressure coil current is compensated using compensating coil.
capacitor is connected in pressure coil to reduce the error due to pressure coil inductance.
control torque is made very small.

Answer / k.prakashchandra

LPF -low pf UPF- unity pf.In lpf meter pf compensation is
done and is accurate at the specified low pf.

Answer / suresh

HERE LPF USED TO measure the low current & UPF is used to measure the high current. Then low pf and unity power factor

Answer / subha

can i get the expansion of lpf and upf

What kinds of decision are made about CT from it's Knee point(voltage & current)?

2 Answers  

what is meant by directional earth fault and non directional earth fault? describe both.

0 Answers  

Explain about p.t?

0 Answers  

What is the need of generator relay panel

0 Answers   Newell,

Hi My dear all Friends, There is a question regarding HVAC Engineering and widely used in Power Projects. Question- What is the diffrence Between REF, SEF and Differential Protection....???? Where REF - Restricted Earth Fault SEF - Senstive Earth Fault.

0 Answers  

Grounding. Dear all at one of my site we checked the amps at the earthing cable to the alternator it was found 125 to 130 A. at the neutal cable in same machine found 146A. in the same plant checked the earthing current on other alternator it was 52A, and neutral 116 A. we are facing problems with our controller and the card was damaged once. can that neutral/GND current be a reason? as there is common grounding for the Alternator,Brkr panel,Transformer?

2 Answers  

How to make two bulbs glow Alternatively?

2 Answers  

Two liquids hot and cold in two vessels are there and an metal bar acts as a conductor of heat between the two vessels. what happens then. what happens after 24 hrs?

0 Answers  

How transformer neutralshould earthed ? Transformer neutral connected to earth mat in substations, right or wrong ?

4 Answers  

what happens if commutator is removed in an dc machine?

3 Answers  

Why we transmit the power at the voltage in the multiple of 11 or 1.1 like 11kv, 22kv, 66kv, 132kv...... some one told me that it is due to fomr factor 1.1 of sine wave. its fine but while transforming we can choose any voltage, so why only multiple of 1.1 there also.......? plz tell me.

7 Answers  

which type of winding is used for high voltage & low current?

1 Answers   GEB,