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Topic Title: Negative Voltage Regulation in Transformer
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Created On: 04 November 2013 05:44 PM
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 04 November 2013 05:44 PM
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Joined: 26 October 2013

How can a transformer have negative voltage regulation?
A few texts state that a leading power factor can give rise to negative power factor, but I have not been able to figure out how this is possible.

One vague explanation in my mind is that capacitance across the secondary terminal will somehow cancel out the leakage reactance on the primary side, thus resulting in a higher primary voltage and hence higher secondary voltage as well.

Can somebody please describe more accurately.
 05 November 2013 08:05 AM
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I think I've somewhat become used to the idea of negative voltage regulation after going through lots of articles and also drawing the phasor diagram myself. The main issue seems to be resolved now.

However, I still have confusions as far as the related calculations are concerned. For example, if you have a look at the following link:
Link Removed

According to example 1, full load current = KVA rating/secondary voltage specified in the question statement. Thus in this case, he has assumed 125V to be the full load voltage. However, in another place (part ii), he considers 125V to be the no load voltage while calculating the secondary terminal voltage.

Is this a mistake, or did he make this assumption because the value of current would not differ by too much even if no load voltage were used in the calculation?
 05 November 2013 06:50 PM
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I am not quite sure about your negative voltage regulation in a transformer? To me such an expression means that the output voltage is increased as the load current is increased?

I have encountered such a problem only in association with feedback; indeed my very first encounter was with an amplifier in a small lab on the third floor of a large building - an overlong Earth connection - coupled with a mixup in my pluggery-buggery. A proportion of the output signal was appearing on the "Earth" connection and from there wormed his way back via the feedback network - too long ago to give any greater detail.

If I have interpreted your query correctly then you must have a feedback path with some amplification - not necessarily active

Hope this helps to clarify rather than to further mystify?

Ken Green

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