R1
jX1
j0.5X2
j0.5Xm
0.5R2
?
SF
Vo
j0.5X2
0.5R2
j0.5Xm
SB
?
Figure 1: Circuit model for single phase induction motor for Problem 1.
Problem 1: Application - 50%
A single-phase induction motor is used to directly drive the blades of a blender connected
to a 60 Hz wall outlet in a kitchen. When the blender is turned on, the blades turn at 3600
rpm. When frozen strawberries are added, the blades slow down to 2160 rpm. The motor
model parameters are as follows: R? = 2?, R? = 2.8?, X? = 2.56?, X? = 2.56?,
Xm = 60.5?.
a) How many poles does the motor have?
b) What is the forward slip, $s_f$, when the blender is first turned on?
c) What is the reverse slip, $s_b$, when the blender is first turned on?
d) What is the forward slip, $s_f$, when the strawberries are added?
e) What is the reverse slip, $s_b$, when the strawberries are added?
Figure 1 shows the full model of the single-phase induction motor.