Anonymous
Anonymous asked in 科學及數學其他 - 科學 · 1 decade ago

Principle of transformer

1. How does the transformer incorporate the principle of mutual induction?

2. What is the effect on power, voltage and current in BOTH circuit if

i) no. of turns of primary coil is increasing?

ii) no. of turns of secondary coil is increasing?

iii) there is magnetic flux leakage?

iv) there are more loads in secondary circuit?

Why?

3. Should a.c. or d.c. be applied to a transformer?

4. How is eddy current formed in the soft iron core?

I hope my questions are understandable and reasonable. Please answer with reference to a step up transformer.

1 Answer

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  • 1 decade ago
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    1. How does the transformer incorporate the principle of mutual induction?

    There are coils wound around soft iron core, when primary coil conducts electric current, magnetic flux produced and cut accross the secondary coil which induced current flow.

    2. What is the effect on power, voltage and current in BOTH circuit if

    i) no. of turns of primary coil is increasing?

    basically primary VA = secondary VA, if primary coil turns increased, secondary voltage will also increases.

    ii) no. of turns of secondary coil is increasing?

    same as above, if secondary coil turns increased, but no primary voltage increases, then both VA must be the same, secondary current must be decreased.

    iii) there is magnetic flux leakage?

    when flux leakage, there is a lost of power, so primary VA =/= secondary VA.

    iv) there are more loads in secondary circuit?

    if secondary loading increased, that's mean secondary current increased, then to keep the VA in primary, primary current must also increased.

    Why?

    3. Should a.c. or d.c. be applied to a transformer?

    of course a.c., electric current only produced when magnetic flux cutting accross the conductor(coil), when there is no change in magnetic flux, no more current flows. As a.c. is always changing from + to -, and from - to +, so only a.c. can be applied to transformer.

    4. How is eddy current formed in the soft iron core?

    Eddy currents are created when a moving conductor experiences changes in the magnetic field generated by a stationary object, as well as when a stationary conductor encounters a varying magnetic field. Both effects are present when a conductor moves through a varying magnetic field, Eddy currents will be generated wherever a conducting object experiences a change in the intensity or direction of the magnetic field at any point within it, and not just at the boundaries.

    I hope my questions are understandable and reasonable. Please answer with reference to a step up transformer.

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