Electromechanical Energy Conversion | Electrical Machine
Q1. For electromechanical energy conversion process , it is essential that coupling magnetic field reacts on ?
a) Electrical system
b) Mechanical system
c) Both electrical & Mechanical systems
d) electrical or mechanical system ✔️
Q2. In order to extract energy from an electrical system , the coupling magnetic filed must reacts with ?
a) electrical system
b) mechanical system ✔️
c) Both electrical and mechanical system
d) either (a) & (b)
Q3. Singly and doubly excited magnetic system are respectively ?
a) loud - speakers and tachometers
b) Synchronous motor and moving iron instruments
c) d.c shunt machines and solenoids
d) reluctance motor and synchronous motor ✔️
Q4. The developed electromagnetic force and/or torque in electro - mechanical energy conversion system act in a direction tends to ?
a) increase the store energy at constant flux
b) decrease the store energy at constant flux ✔️
c) decrease the co-energy at constant mmf
d) increase the co-energy at constant mmf
Q5. In a electric machine , if L = slot length and D = slot depth , then slot leakage flux is proportional to
a) 1 / LD
b) LD ✔️
c) D / L
d) L / D
Question and Answer of Electromechanical Energy Conversion
Q1. What is the effect of electromagnetic force or torque that develops in any physical system ?
Ans- Electromagnetic force or torque developed in any physical system acts in such a direction as to tend to :
a) decrease the magnetic stored energy at constant φ or ψ which can be supplemented by the following parametric equations
b) Increase both filed energy stored and co-energy at constant current or mmf.
c) Decrease the reluctance
d) increase the permanence and inductance
e) decrease current i at constant flux linkages ψ or increase ψ at constant i
Q2. A coil of 1000 turns on a core would create a flux of 2 m Wb when carrying a current 1A. Calculating the energy stores in the magnetic field .
Ans - by the question
N = 1000 φ = 2 m Wb i = 1A
Energy stored in mechanical field = Niφ = 1000 * 1 * 2 * 10 ^ -3 = 2 J
Q3. Distinguish between singly - exited and doubly exited systems.
Ans -
single exited system - in a slightly exited system , the electric field acts as a coupling medium between electrical and mechanical system . in this case if a coil is wound around a magnetic core connected to a voltage source , the ferromagnetic rotor experiences a torque using it towards a region where the magnetic field is stronger. That is a torque is exerted on the rotor so that it tries to positions itself to give minimum reluctance for the magnetic flux . the reluctance is dependent upon the rotor angle .
Doubly exited system -
1. A doubly exited magnetic system has two independent sources of excitations.
2. Example of synchronous machines d.c shunt machines , loudspeakers , tachometers etc . in a doubly excited system a torque is produced by the coalignment of two magnetic fields.
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