Doubts in Power Transformer

aarthivg
Member • Aug 12, 2013

Doubts in Power Transformer

I have some doubt in power transformer relating it with the frequency.

1. what will happen to the power transformer which is designed for 50 hz is connected to 100 Hz source.

2. What will happen to the power transformer which is designed for 50 HZ is connected to a 10 HZ source.

3. Why Iron Losses are constant at all loads in a transformer.

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Jeffrey Arulraj

Member • Aug 12, 2013

50 Hz design when connected to higher frequency source the variation in saturation current will become lower=> Efficiency will fall => Losses will increase

10 HZ Core saturation occurs resulting in destruction of power transformer due to cumulative increase in current in core

Iron losses are constant only till the core resistance is constant. If resistance is constant then losses are constant otherwise there is a shift in losses

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lal

Member • Aug 14, 2013

Why Iron Losses are constant at all loads in a transformer?
Iron loss comprises of eddie current loss and hysteresis loss.

Hysteresis loss depends on the rate of change of direction of flux and the magnetic property of material used. Clearly, frequency is fixed and hence the rate of change of flux reversal too. And the material used for construction of the core doesn't change its magnetic properties with time. So hysteresis loss can be safely considered to be fixed in normal working conditions.

Eddie current loss is, but, dependent on the current flowing through the conductors. But transformer cores are made of laminations insulated from one another. This is to reduce eddie current loss. In fact it is assumed that the eddie current losses are negligible that its value is constant for any value of load current flowing through the conductors.

Well, yeah! Hence our conclusion - Iron loss is assumed to be constant at all loads for a transformer.

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pinank

Member • Aug 22, 2013

lal
Iron loss comprises of eddie current loss and hysteresis loss.

Hysteresis loss depends on the rate of change of direction of flux and the magnetic property of material used. Clearly, frequency is fixed and hence the rate of change of flux reversal too. And the material used for construction of the core doesn't change its magnetic properties with time. So hysteresis loss can be safely considered to be fixed in normal working conditions.

Eddie current loss is, but, dependent on the current flowing through the conductors. But transformer cores are made of laminations insulated from one another. This is to reduce eddie current loss. In fact it is assumed that the eddie current losses are negligible that its value is constant for any value of load current flowing through the conductors.

Well, yeah! Hence our conclusion - Iron loss is assumed to be constant at all loads for a transformer.
Hey I certainly agree with your point about the losses..but I would like to draw your attention about the leakage reactance of the transformer...we consider Xl=2πfL..so won't the frequency affect the net leakage reactance or even the magnitizing reactance of the transformer..as it is proportional to the frequency..so lesser the frequency lesser has to be the losses..

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lal

Member • Aug 22, 2013

Definitely it depends. But here the question was "Why Iron Losses are constant at all loads in a transformer?"

Frequency doesn't change with load. Hence the leakage reactance should be constant. That implies Iron loss due to lekage reactance can be considered constant at all loads.

But as you said, if the frequency of ac supply changes, that varies the leakage reactance and hence the losses too.

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pinank

Member • Aug 22, 2013

Lol...acha is there any method by which we can measure the leakage reactance in a transformer..I mean, if we can measure the reactance value real time we can deduce the power losses and various other parameters!

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Jeffrey Arulraj

Member • Aug 22, 2013

I am sure testing done in the transformer will help you in predetermining under any condition the transformer is operated

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