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Basically at noloads the current value is less so we use lpf at no loads
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Why does not wattmeter measure the reactive power?
A wattmeter is designed so that it measures the supply voltage and the in-phase component of the load current. The product of these two quantities is the true power of the load.
How would you measure power using three watt meter and one watt meter for balanced and unbalanced loads?
The 'one wattmeter method' can only be used for balanced, wye-connected, loads where the load's neutral point is accessible. The wattmeter's current coil is inserted into any line conductor, and the voltage coil is connected between the same line and the neutral point. The wattmeter reading indicates the power of one phase, so the total power is three times the wattmeter reading.To measure the total power of a balanced or unbalanced wye- or delta-connected load, it is only necessary to use twowattmeters -this is called the 'two wattmeter method'. In this case, the current coils of each wattmeter are inserted into any two line conductors, and the voltage coils are connected between the two line conductors and the third line conductor. The sum of the two wattmeter readings will indicate the total power of the load.
What instrument can you use to measure reactive power of a load?
An ammeter and a wattmeter are the instruments needed.
What does wattmeter indicate in blocked and no load test?
A water meter that says no load test means one thing. The thing that it means is iron loss.
Is wattmeter reading under no load test is equal to iron loss of the transformer?
Yes; that is the principle used in no-load tests on transformers. The current in the copper windings is zero on the secondary and low on the primary, so the copper loss is negligible.
Why is LPF wattmeter used for no load test?
In case of no load only magnetizing current is flowing which is somewhere around 75 degree out of phase and so the power factor is very low.
What is difference between lpf and upf wattmeters?
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 is given by :Er. M KUMAR YADAV
Is there any difference in values between the two wattmeter method and three wattmeter method if you apply these two methods in same load?
Blondel's Theorem states that you can have one less wattmeter than there are conductors supplying a balanced or unbalanced load. In either case, the sum of the wattmeter readings will give you the total power of the load.
What quantity is watt measured in?
A wattmeter is used to measure the power of a load.
Why does not wattmeter measure the reactive power?
A wattmeter is designed so that it measures the supply voltage and the in-phase component of the load current. The product of these two quantities is the true power of the load.
Why UPF wattmeter is used in SC test?
UPF(Unity Power Factor) is connected as the power factor is 1. Unlike OC where quantum dynamic rules apply in SC the time space gravitational lensing takes place which is why only LPF can be used.
Why watt-meter is required to measure real power delivered to a purely resistive load?
A wattmeter (not 'watt-meter') will always measure the true power of a load, regardles of whether that load is purely resistive or not. This is because a wattmeter effectively measures the in-phase component of the load current.
How would you measure power using three watt meter and one watt meter for balanced and unbalanced loads?
The 'one wattmeter method' can only be used for balanced, wye-connected, loads where the load's neutral point is accessible. The wattmeter's current coil is inserted into any line conductor, and the voltage coil is connected between the same line and the neutral point. The wattmeter reading indicates the power of one phase, so the total power is three times the wattmeter reading.To measure the total power of a balanced or unbalanced wye- or delta-connected load, it is only necessary to use twowattmeters -this is called the 'two wattmeter method'. In this case, the current coils of each wattmeter are inserted into any two line conductors, and the voltage coils are connected between the two line conductors and the third line conductor. The sum of the two wattmeter readings will indicate the total power of the load.
What is effect of power factor on the readings of wattmeter?
If you are asking whether power-factor improvement has any effect on a wattmeter reading, then the answer is no, it doesn't. Improving the power factor of a load has absolutely no effect on the power of the load, but it can act to reduce the value of the load current.
Why you use low power factor wattmeter on primary and unity power factor on secondary side of transformer?
There is no such thing as a 'low power-factor' wattmeter. A wattmeter always reads true power, regardless of the load's power factor.
Does a wattmeter indicate real or apparent power?
As its name implies, a 'wattmeter' measures 'real' or 'true power'. It does this by measuring the supply voltage and the in-phase component of the load current.
Why do you use two phase watt meter?
You may be thinking of the 'two-wattmeter method' for measuring three-phase power?As a rule, it's always possible to use one less wattmeter than the number of conductors supplying a three-phase load to measure the power of that load. So, for a three-phase, three-wire, system, two wattmeters may be used to measure the total active power of the load -regardless of whether the load is balanced or unbalanced. The algebraic sum of the two wattmeter readings will give the total power.
