Concept of General Terms Pertaining To Rotating Machine Question - Electrical4u

 Concept of General Terms Pertaining To Rotating Machine | Electrical Machine 

Q1. For a p-pole machine , the relation between electrical and mechanical degrees is given by 

a) n × full pitch 

b) 1 /n × full pitch ✔️

c) 2 /n × full pitch 

d) 3 /n × full pitch 

Q2. A Pole pitch in an Electrical Machine Is 

a) = 180⁰  electrical ✔️

b) = 180⁰  mechanical

c) > 180⁰  electrical

d) < 180⁰  electrical

Q3. One Turn Consist of 

a) two coil sides 

b) two conductors ✔️

c) four conductors 

d) four coil sides 

Q4. For P - Pole machine , the relation between electrical and mechanical degrees is given by 

a) θ_elec = 4/P θ_mech 

b) θ_elec = 2/P θ_mech 

c) θ_mech  = P/2 θ_elec

d) θ_elec = P/2 θ_mech ✔️

Q5. For a p - pole machine the relation between electrical & mechanical angles is given by 

a)  θ_elec = 4/P θ_mech 

b) θ_elec = 2/P θ_mech 

c)  θ_elec  = P/2 θ_mech ✔️

d) θ_elec = Pθ_mech 

Q6. Skew is used in Induction motor in order to reduce 

a) Time Harmonics 

b) Space Harmonics 

c) Slot Harmonics

d) None of Above ✔️

Q7. A coil Consists Of 

a) two coil sides ✔️

b) two conductors 

c) four turns

d) two turns 

Q8. The main advantage and Distributing the winding in slots is to 

a) Add mechanical strength to the winding 

b) Reduce the amount of copper required 

c) Reduce the Harmonics in the generated emf  ✔️

d) Reduce the size of the machine 

Q9. The Armature mmf wave for a d.c machine is 

a) Sinusoidal and rotates w.r.t Armature 

b) Sinusoidal and rotates w.r.t Field 

c) Triangular and rotates w.r.t Armature ✔️

d) Triangular and Stationary w.r.t Armature 

Q10. The Chording angle for eliminating 5th harmonic should be 

a) 30⁰ 

b) 34⁰

c) 35⁰ 

d) 36⁰ ✔️

Short Answer type Question

Q1. Define Pitch & Winding factor 

Solution - 

Pitch Factor - It is defined as the ratio of resultant e.m.f of a Chorded coil to the resultant e.m.f had the same coil been full - Pitched 

Kp = Resultant Emf of a Chorded Coil / Resultant e. m. f Of a full pitched coil 

      = (2 E cos e/2) / 2E 

      =  Cos e / 2

The chording angle is e⁰  for fundamental flux wave and for nth space field harmonic , the chording angle becomes ne⁰ electrical . Therefore , the pitch factor for nth Harmonic is 

       Kpn = cos.ne/2

The Advantage of using fractional pitch winding are

1. Reduction in the copper for overhung . this result is less cost of the machine 

2. Reduction of harmonics in the generated e.m.f wave , there by rendring the output e.m.f wave almost a sine wave 

Winding Factor - The product of distribution factor Kd and the pitch factor Kp is referred to as the winding factor and may be donated as Kw . 

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