Explain What will happen when direction of field current is changed (i.e, fiel

Explain What will happen when direction of field current is
changed (i.e, field excitation is reversed) in the
following machines?
1) Alternator
2) Synchronous Motor
3) D.C Generator ( Shunt or Seies )
4) D.C Motor ( Shunt or Seies )

Question Posted / anil

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Explain What will happen when direction of field current is changed (i.e, field excitation is reve..

Answer / tpfasil200

Direction of rotation of synchronous motor is determined b y its starting direction,as initiated by inducyion motor action. Thus, to reverse the direction of a 3 phase synchronous motor, it is necessary to first stop the motor and then reverse the phase sequence of the 3 phase connections at the stator. REVERSING THE CURRENT TO FIELD WINDINGS WILL NOT AFFECT THE DIRECTION OF ROTATION

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Explain What will happen when direction of field current is changed (i.e, field excitation is reve..

Answer / tpfasil200

Direction of rotation of dc motor can be reversed in 2 ways
1.reversing current through armature and interpole windings(if they exist)
2.reversing current through field windings,ie,through shunt and/or series winding..but not through interpole windings(if they exist)
Reversing current through the armature is preferred because reversing current through the field windings involves breaking and making highly inductive currents of the field windings.Also field reversal of compound motors requires connections of both shunt and series windings to be changed..

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Explain What will happen when direction of field current is changed (i.e, field excitation is reve..

Answer / prasanth

1.in alternator the induced emf is reduced due to retentive property of the field magnet when reversed.

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