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This set of Electrical Machines Multiple Choice Questions & Answers
(MCQs) focuses on “Gene EMFâ€Â.
1. Which of the following statements is/are correct regarding the generation
of EMF in rotating electrical machines in the armature winding? EMF is
gene
a) by rotating armature windings through a magnetic field
b) by rotating magnetic field with respect to the armature windings
c) by designing the magnetic circuit to have variable reluctance with rotor
rotation
d) any of the mentioned
View Answer
Answer:d
Explanation: Any of the above mentioned methods will produce EMF in the armature windings.
2. The EMF equation e = NÉrΦsinÉrt is applicable to
a) AC systems with time variant field flux
b) DC systems with time variant field flux
c) both AC and DC systems with time invariant field flux
d) both AC and DC systems with time variant field flux
View Answer
Answer:c
Explanation: e = NÉrΦsinÉrt-NdΦ/dtcosÉrt, for time invariant field flux dΦ/dt = 0 ⇒ e = NÉrΦsinÉrt, is the general equation, and is
applicable to both AC and DC systems.
3. In the equation for RMS value of the gene EMF in a full pitched coil
of an AC machine,
E = Emax/√2 = √2ÀfrNΦ, fr depends on
a) rotating speed of the armature coil
b) rotating speed of the flux density wave
c) relative velocity between the flux density wave and armature coil
d) any of the mentioned
View Answer
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