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1. ESO-203A: Introduction to Electrical Engineering (2014-2015, II Semester)
Assignment No. # 10
1. A three-phase, 2000 V, Y-connected, 2-pole, 50Hz,wound-rotor induction motor has the
following no-load and blocked-rotor test data:
No-load: 2000 V 15.3 A 10.1 kW
Blocked-rotor: 440 V 170 A 36.4 kW
The ac resistance of the stator winding is 0.22 Ω per phase. Calculate all the necessary
data for the 1-phase equivalent circuit at a slip of 2% and draw the circuit showing all the
parameter values.
2. Using the parameters obtained in Q.1, determine
a) Starting current and starting torque, when started direct-on-line at full voltage.
b) Full load current, full load power factor, full load mechanical torque at a slip of 0.02.
c) Slip at which maximum torque is developed and the maximum torque value.
d) The external resistance required in the rotor circuit so that maximum torque occurs at
start.
3. The nameplate specifications for a single-phase capacitor-start induction motor are
1110 V, 0.5 hp, 1720 rpm, 8.0 A, 60 Hz. The following test data are obtained for this
motor:
Stator main winding resistance = 2.0 Ω
Blocked rotor test (auxiliary winding disconnected):
V = 52 V, I = 8.0 A, P= 255 W
No-load test:
V = 110 V, I = 4.5 A, P = 100 W
a) Obtain the double revolving field equivalent circuit for the motor.
b) Determine the no-load rotational loss.
4. A 10.25 hp, 115 V, 1725 rpm, 60 Hz, four-pole, capacitor-start induction motor has
the following equivalent circuit parameters for the main winding.
R1 = 2.2 Ω, R2’ = 3.5 Ω
X1 = 2.5 Ω, X2’ = 2.5 Ω, Xmag = 60 Ω
The core loss at 115 V is 20 W and the friction and windage loss is 15 W. The motor is
connected to a 115 V, 60 Hz supply and runs at a slip of 0.04. While running, the starting
winding remains disconnected. Determine the speed, input current, power factor, input
power, developed torque, output power, efficiency, and rotor copper loss.
5. A single-stack, four-phase (stator) stepper motor is required to produce an 18o
step
motion (full step). Determine the number of rotor poles and the sequence of excitation of
the stator phases.
6. A three-stack, four-pole stepper motor has eight teeth on the rotor as well as the stator.
Determine the step size as excitation is changed from one stack to the next.