internal power factor

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anuj

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What is meant by the internal power factor of a transformer or internal pf of a synchronous generator
 
I'll give this a shot.

Anytime you have inductive properties you will have reactive current, if you have reactive current you have power factor.

Even though these items are considered a voltage source or a device for conversion from one voltage to another instead of a load, there is still reactive current just like there is in a motor.
 
anuj said:
What is meant by the internal power factor of a transformer or internal pf of a synchronous generator
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Never heard the term of power factor as used with a transformer. Transformers are rated in Kva. Simply put, the max amperage that can run through it at a given voltage. Increase the PF of the load and get more capacity out of the transformer.
 
Canton said:
Never heard the term of power factor as used with a transformer. Transformers are rated in Kva. Simply put, the max amperage that can run through it at a given voltage. Increase the PF of the load and get more capacity out of the transformer.
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How much current is drawn on primary circuit when there is no load on the secondary circuit?

A little of that current is resistive in nature and gives up heat, the rest is reactive current that does no real work.

Now place full load resistive load on the secondary and the primary still has some reactive current present, but the level of reactive current is so low compared to the true power current that you have high power factor.
 
141111-2114 EST

A particular 175 VA 120 V primary unloaded transformer with with 123 V input has a PF = 0.21 .

A surprising result I had not expected. At 100 V the PF increased to 0.25, and at 130 V PF dropped to 0.16 .

Is Kill-A-Watt EZ giving me bad readings? Probably not. With a load of 30 mfd shunted with 460 ohms the EZ PF reading remained at 0.18 from 100 V to 130 V.

Why the transformer has the above characteristic will have to wait for some future analysis.

.
 
@kwired
So u are saying that internal pf is because of magnetising current Im + load current in loaded situation
in loaded situation. (If Neglecting copper loss)
Am I right ?

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I would say that the internal power factor would be the result of the inductive component and the resistive component of the magnetizing current in an unloaded situation. Neglecting copper loss would produce an even lower value if PF corresponding just to the hysteresis losses.
AHA! As long as you stay well below core saturation, the hysteresis losses will occur in the low field region, and therefore be proportionally greater the lower the amplitude of the current.
That fits gar's observation.
 
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gar said:
141111-2114 EST

A particular 175 VA 120 V primary unloaded transformer with with 123 V input has a PF = 0.21 .

A surprising result I had not expected. At 100 V the PF increased to 0.25, and at 130 V PF dropped to 0.16 .

Is Kill-A-Watt EZ giving me bad readings? Probably not. With a load of 30 mfd shunted with 460 ohms the EZ PF reading remained at 0.18 from 100 V to 130 V.

Why the transformer has the above characteristic will have to wait for some future analysis.

.
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I have actual test data on a 400kVA unit.
It's a Ddyn11.

No load power factor is sort of comparable with yours at 0.16.
But, in real world terms, something of an irrelevance given that no load losses amount to about 0.3% of the rating.
 
gar said:
141111-2114 EST

A particular 175 VA 120 V primary unloaded transformer with with 123 V input has a PF = 0.21 .

A surprising result I had not expected. At 100 V the PF increased to 0.25, and at 130 V PF dropped to 0.16 .

Is Kill-A-Watt EZ giving me bad readings? Probably not. With a load of 30 mfd shunted with 460 ohms the EZ PF reading remained at 0.18 from 100 V to 130 V.

Why the transformer has the above characteristic will have to wait for some future analysis.

.
Click to expand...
A transformer at no load is a rich source of harmonics. So testing with a harmonic analyser rather than Kill-A-Watt EZ would give a clue to the riddle.
 
141113-0953 EST

Sahib:

What is the point of your post?

The subject of the thread is "internal power factor". At this time I don't believe we yet have a definition of this term. It has been conjectured that it is possibly the unloaded input power factor of the transformer.

If the subject is power factor, then why do you go on a tangent.

.
 
gar:
My point is, as demonstrated by your post#5, the so called internal power factor of a supply equipment such as transformer may not have a constant power factor for all loads. Its own power factor value i.e its internal power factor depends on the nature of load it supplies or it does not supply in which case on the supply voltage.
(The harmonic issue I brought up in my last post is to ascertain whether the power factor values you mentioned in your post were attributable to the fundamental components or not.)
 
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Transformers are typically rated in VA which includes power factor of the load. Additional PF added by the transformer is usually negligible when talking about full load rating values.

Generators are typically rated in watts and possibly may not handle full load watts if it is at a poor power factor.

Don't know if this is part of what OP is asking about or not.
 
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