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The no load power factor would tell you the ratio of losses vs. excitation current. I'm not sure that this really has any value from a performance standpoint.
AnswerAt no load, i.e. with the secondary windings open-circuited, the primary current, Io, comprises the magnetising current, Im, which is in phase with the flux and lags the supply voltage by 90o, and an iron-loss current, Io, which is in phase with the supply voltage. As Im is very much greater than Ii, the primary current, Io, lags by very nearly 90o. So, the power factor of a transformer on no load is approaching 0 lagging.
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What is the condition for zero voltage regulation of a single phase transformer?
zero volatge regulation means the terminal volatge of transformer at full load on a given power factor become equal to the rated teriminal volatge of transformer , it happens only for leading power factor in transformer
Why unity power factor is used in load test?
When power factor is at unity, the voltage and current waves are aligned or in phase with one another. Since power is the product of voltage and current, power transfer is maximized at unity power factor. When power is transmitted at a lower power factor, greater current is required to deliver the same amount of power. When current is increased, the size of the transmission, distribution and generation systems, all have to be increased accordingly, along with the price of the killowatt-hour at the meter.
What significance has a power factor in an unbalanced system?
A three-phase 'unbalanced' system refers to the load, as the supply voltages are unaffected by load. So the phase-angle and, therefore, the power factor of each phase will be different -i.e. there will be three different power factors.
How you measure power factor in three phase load by two wattmeter method?
First of all, you can only measure power factor of a three-phase load, provided that it is balanced load. The power factor can then be found by determining the cosine of the phase angle, using the following equation:tan (phase angle) = 1.732 ((P2-P1)/(P2+P1))...where P1 and P2 are the readings of the two wattmeters.
Why transformer is measured in kva?
The rating of the machine (kva or kw) depends upon the power factor, since the load power factor to which the transformer is supplying power is not known, it may be capacitive, inductive, or resistive that is why its rating is in kva not in kw.
What is the condition for zero voltage regulation of a single phase transformer?
zero volatge regulation means the terminal volatge of transformer at full load on a given power factor become equal to the rated teriminal volatge of transformer , it happens only for leading power factor in transformer
Why transformer power factor taken unity?
It isn't! A transformer operating at no load has a very low power factor.
Why power factor can not be unity?
Power factor can be unity. If the load is purely resistive, then the load current and supply voltage are in phase, and the load will have unity power factor.
Does low load in transformer lead to low power factor?
Power factor is determined by the nature (resistive, inductive, capacitive) of a load, not whether it is a low load or a high load.
What is the power factor when the current and voltage are in phase?
The power factor of a load is the cosine of the angle by which the load current lags or leads the supply voltage. So if they are in phase (phase angle is zero), then the power factor must be unity (1).
What condition you get negative regulation for transformer?
When its load has a leading power factor.
When is a transformer closet to unity power factor?
When it supplies a resistive load.
Why does the power factor of the load effects the V.R. of transformer?
With varying power factor the load current drawn changes, which in turn affects the voltage regulation
Why you use upf wattmeter for short circuit test on load test on single phase transformer?
If, by 'upf', you mean 'unity power factor', then allwattmeters measure the in-phase component of the load current, so the term is quiet unnecessary.A short-circuit test is used to determine the (true) power loss in the transformer, which is exactly what a wattmeter measures
Why unity power factor is used in load test?
When power factor is at unity, the voltage and current waves are aligned or in phase with one another. Since power is the product of voltage and current, power transfer is maximized at unity power factor. When power is transmitted at a lower power factor, greater current is required to deliver the same amount of power. When current is increased, the size of the transmission, distribution and generation systems, all have to be increased accordingly, along with the price of the killowatt-hour at the meter.
What significance has a power factor in an unbalanced system?
A three-phase 'unbalanced' system refers to the load, as the supply voltages are unaffected by load. So the phase-angle and, therefore, the power factor of each phase will be different -i.e. there will be three different power factors.
What are common efficiencies for transformers?
Transformer utilization factor is the ration of power delivered to the load and ac rating of the transformer secondary.
