Electrical Machines Questions and Answers – Elementary Synchronous Machines

This set of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Elementary Synchronous Machines”.

1. Consider a single phase synchronous machine of cylindrical rotor type. A single phase supply is given to the stator winding and a voltmeter is connected across rotor winding. For what value of θ_r, the voltmeter reads maximum?
a) 90°
b) 0°
c) 45°
d) 30°
View Answer

2. Consider a single phase synchronous machine of cylindrical rotor type. A single phase supply is given to the stator winding, and a voltmeter is connected across rotor winding. For what value of θ_r the voltmeter reads a zero?
a) 0°
b) 30°
c) 45°
d) 90°
View Answer

3. Which of the following equation best represents the mutual inductance between stator and rotor in a single phase cylindrical rotor synchronous machine? (where θ_r= space angle between stator and rotor field axis)
a) M_sr=0
b) M_sr=M_max
c) M_sr=M_maxcosθ_r
d) M_sr=M_maxsinθ_r
View Answer

4. In a single phase cylindrical rotor synchronous machine, the torque T_e tends to ____________ the space angle θ_r.
a) reduce
b) increase
c) maintain constant
d) all of the mentioned
View Answer

5. The following torque expression: T_e=-i_si_rM_maxsinθ_r is applicable in a single phase cylindrical rotor synchronous machine when the rotor is __________
a) revolving
b) stationary
c) revolving or stationary
d) none of the mentioned
View Answer

6. In a two phase cylindrical rotor synchronous machine, the self inductances L_α, L_β for phases α,β respectively are __________
a) constant and equal
b) constant and unequal
c) varying and equal
d) varying and unequal
View Answer

7. In a two phase cylindrical rotor synchronous machine, the mutual inductance M_αβ between α phase and β phase winding is __________
a) M_max
b) 0
c) M_min
d) any of the mentioned
View Answer

8. In a two phase cylindrical rotor synchronous machine, torque T_e is _____________
a) constant at some instant of time
b) changing at every instant of time
c) constant at every instant of time
d) changing at some instant of time
View Answer

9. Which of the following equation represents the reluctance torque of a salient pole synchronous machine?
a) T_e(av) = 1/4 I_m²(L_d-L_q)sin2δ
b) T_e(av) = 2 I_m²(L_d-L_q)sinδcosδ
c) T_e(av) = 1/8 I_m²(L_d-L_q)
d) T_e(av) = 1/8 I_m²(L_d-L_q)sin2δ
View Answer

10. Which component of torque equation, T_e(av) = 1/8 I_m²(L_d-L_q)sin2δ+1/2 I_fI_mM_maxsinδ represents the electromagnetic/interaction torque in single phase salient pole synchronous machine?
a) 1/2 I_fI_mM_maxsinδ
b) 1/8 I_m²(L_d-L_q)sin2δ
c) 1/8 I_m²(L_d-L_q)sin2δ + 1/2 I_fI_mM_maxsinδ
d) none of the mentioned
View Answer

11. An electromechanical energy conversion device has cylindrical stator but salient pole rotor. If δ is the angle between stator field and rotor field, the average torque developed is proportional to (A and B are constants) __________
a) Asinδ
b) Asin2δ
c) Asinδ+Bsin2δ
d) δ
View Answer

12. An electromechanical energy conversion device has cylindrical stator but salient pole rotor. Rotor is not excited. If δ is the angle between stator field and rotor long axis, then average torque developed is proportional to (A and B are constants).
a) Asinδ
b) Asin2δ
c) Asinδ + Bsin2δ
d) zero
View Answer

13. The self and mutual inductances of a doubly excited magnetic system are L_s=0.6+0.20cos2θ_r H and L_r=0.75+0.30cos2θ_r H and M_sr=0.8cosθ_r H. For a stationary rotor at an angular position of θ_r=60°,what is the magnitude of torque when the currents i_s=20A DC and i_r=10A DC?
a) -233.88N-m
b) +233.88N-m
c) -467.76N-m
d) +467.76N-m
View Answer

Sanfoundry Global Education & Learning Series – Electrical Machines.

To practice all areas of Electrical Machines, here is complete set of 1000+ Multiple Choice Questions and Answers.