Worksheet4
.pdf
School
Addis Ababa University**We aren't endorsed by this school
Course
ECEG 3202
Subject
Electrical Engineering
Date
Jan 11, 2025
Pages
1
Uploaded by AdmiralHorse4827
Addis Ababa UniversityAddis Ababa Institute of TechnologySchool of Electrical and Computer EngineeringElectrical Machines and Drives: ECEG-3202Worksheet-41. A balanced three-phase,50−Hzvoltage is applied to a3 phase,4 pole, induction motor. Whenthe motor is delivering rated output, the slip is found to be0.05. What is the speed of the rotorm.m.f. relative to the rotor structure?(Ans: 75 rpm)2. The synchronous speed for a3 phase 6-poleinduction motor is1200rpm. If the number of polesis now reduced to4with the frequency remaining constant, what will be the rotor speed with aslip of5%?(Ans: 1710 rpm)3. The rotor power output of a3-phaseinduction motor is15KWand corresponding slip is4%.What is the value of rotor copper loss?(Ans: 625 watt)4. The power input to a500V,50Hz,6 pole 3 phasesquirrel cage induction motor running at975rpmis40KW. The stator losses are1KWand the friction and windage losses are2KW.Calculate,(a) Slip(b) Rotor copper loss(c) Mechanical power developed(d) The efficiency(Ans: (a) 0.025, (b) 975 kW, (c) 36.025 kW, and (d) 90%)5. The shaft output of a three-phase60−Hzinduction motor is80KW. The friction and windagelosses are920W, the stator core loss is4300Wand the stator copper loss is2690W. The rotorcurrent and rotor resistance referred to stator are respectively110Aand0.15 Ω. If the slip is3.8%, what is the percent efficiency?(Ans: 87.81%)6. A4-pole,3 phase,400V,50Hz, induction motor has the following parameters for its circuitmodel (rotor quantities referred to the stator side):R1= 1.6 Ω,X1= 2.4 Ω,R2= 0.48 Ω,X2= 1.2 ΩandXm= 40 Ω. Rotational losses are720W. Neglect stator copper losses. For aspeed of1470rpm, calculate theinput current,input power factor,net mechanical power output,torqueandefficiency.(Ans:I1= 10.24−35.9◦,pfin= 0.81,Pout= 4490watt,τout= 29.18Nm,and η= 77.39%)7.Assignment!The per-phase equivalent circuit parameters of a208−V,4-pole,60−Hz, three-phase, Y-connected,induction motor areR1= 0.4 Ω,X1= 0.8 Ω,R2= 0.3 Ω,X2= 0.9 Ω, andXm= 40 Ω. The coreloss is45W, and the friction and windage loss is160W. When the motor operates at a slip of5%, determine:(a) the input current,(b) the power input,(c) the air-gap power,(d) the power developed,(e) the power output,(f) the shaft torque, and(g) the efficiency of the motor.
