Join 60,000+ competitive exam aspirants
or with email
Your Cart
SubtotalтВ╣0
TotalтВ╣0
Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
Join 60,000+ competitive exam aspirants
Which of the following statements is/are correct regarding the generation of EMF in rotating electrical machines in the armature winding? EMF is generated ____________
by rotating armature windings through a magnetic field
by rotating magnetic field with respect to the armature windings
by designing the magnetic circuit to have variable reluctance with rotor rotation
any of the mentioned
any of the mentioned
EMF is generated in rotating electrical machines based on the principle of electromagnetic induction, which relies on the relative motion between a magnetic field and a conductor. This relative motion results in a change in magnetic flux linkage, which can be achieved through various mechanical configurations as described in the options.
EMF is generated in rotating electrical machines based on the principle of electromagnetic induction, which relies on the relative motion between a magnetic field and a conductor. This relative motion results in a change in magnetic flux linkage, which can be achieved through various mechanical configurations as described in the options.
e=тИТNdtd╬жтАЛ тАФ Faraday's Law of Electromagnetic Induction
e=Blvsin(╬╕) тАФ Motional EMF induced in a conductor
The fundamental principle is Faraday's law of electromagnetic induction, e=тИТNdtd╬жтАЛ. Whether the coils rotate (as in a DC machine) or the magnetic field rotates (as in an AC synchronous machine), the rate of change of flux linkage remains the physical basis for voltage generation. Variable reluctance machines (like switched reluctance motors) generate EMF by modulating flux linkage through changes in magnetic path geometry rather than continuous induction.
Relative motion is the essential requirement for electromagnetic induction.
In DC machines, armature coils rotate within a stationary magnetic field.
In Synchronous machines, the magnetic field (rotor) rotates relative to stationary armature windings.
Variable reluctance machines utilize the change in inductance L relative to rotor position to induce EMF.
Versatility in machine design for specific torque/speed requirements
Applicability across both AC and DC systems
Complexity increases with non-conventional flux modulation techniques
Requires precise control for variable reluctance machines
DC Generators and Motors
Synchronous Generators (Alternators)
Switched Reluctance Motors
The generation of EMF is independent of the mechanical arrangement as long as the linkage d╬ж/dt exists.
Option C refers to machines like Switched Reluctance Motors (SRM), where v=id╬╕dLтАЛ╧Й+LdtdiтАЛ.
D is correct тАФ The generation of EMF in electrical machines is governed by the principle of relative motion or flux variation, which can be achieved via any of the listed methods.
Always remember that EMF generation is a function of the change in flux linkages. If there is no relative motion (d╬ж/dt = 0), no induced EMF can occur in a steady-state system.