Home | | Basic Electrical and Instrumentation Engineering | | Electrical Engineering and Instrumentation | Solved Problems: Electrical Engineering and Instrumentation - DC Machines

Solved Problems: Electrical Engineering and Instrumentation - DC Machines - | Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail |

Chapter: Electrical Engineering and Instrumentation - DC Machines

Solved Problems: Electrical Engineering and Instrumentation - DC Machines

Electrical Engineering and Instrumentation - DC Machines - Solved Problems: Electrical Engineering and Instrumentation - DC Machines

PROBLEMS

 A 4 pole generator with wave wound armature has 51 slots each having 24 conductors. The flux per pole is 10 mWb. At what speed must the armature rotate to give an induced emf of 0.24 kV. What will be the voltage developed, if the winding is lap connected and the armature rotates at the same speed?

Given data

P = 4

No.of slots = 51

No.of conductors/slot = 20

Eg= 0.24 Kv = 240 V

 

Φ = 10 mW= 10/1000 Web

 

Find N &Eg at same N?

 

Solution

 

Total no. of conductors, Z = 51x20 = 1224

 

Wave winding, A=2

From EMF equation,

 

N= Eg60A / ΦZP = (240x60x2)/(10/1000x1224x4) = 612.75 rpm

 

Lap winding, A=P=4

 

Eg = PΦZN/60A = (4x10/1000x1224x612.75)/(60x4) = 0.125 kV

 

2. A 250 volt DC shunt motor has armature resistance of 0.25 ohm on load it takes an armature current of 50A and runs at 750rpm. If the flux of the motor is reduced by 10% without changing the load torque, find the new speed of the motor.

 

Given data

 

V = 250

Ra = 0.25

Ia = 50

N1 = 750

Φ2 = 90%Φ1

Find N2?

 

Solution


Eb1 = V-Ia1Ra  = 250-(50x0.25) = 237.5V

 

Eb2 = V-Ia2Ra

Load torque is constant

Ta1 = Ta2

 

Φ1Ia1 = Φ2Ia2

 

Ia2 = 55.55A

 

Eb2 = 250-55.55X0.25 = 236.12V

 

N2 = 828 rpm

 

 

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail


Copyright © 2018-2021 BrainKart.com; All Rights Reserved. (BS) Developed by Therithal info, Chennai.