A 440-V, 50-Hz, two-pole, Y-connected induction motor is rated at 75 kW. The equivalent circuit parameters are:
R1 = 0.075 Ģ
R2 = 0.065 Ģ
XM = 7.2 Ģ
X1 = 0.17 Ģ
X2 = 0.17 Ģ
PF&W = 1.0 kW
Pmisc = 150 W
Pcore = 1.1 kW
For a slip of 0.04, find:
(a) The line current IL
(b) The stator power factor
(c) The rotor power factor
(d) The stator copper losses PSCL
(e) The air-gap power PAG
(f) The power converted from electrical to mechanical form Pconv
(g) The induced torque Ģind
(h) The load torque Ģload
(i) The overall machine efficiency Ģ
(j) The motor speed in revolutions per minute and radians per second
Example
The following test data were taken on a 7.5-hp, four-pole, 208-V, 60-Hz, design A, Y-connected IM having a rated current of 28 A.
DC Test:
VDC = 13.6 V
IDC = 28.0 A
No-load Test:
V1 = 208 V
f = 60 Hz
I = 8.17 A
Pin = 420 W
Locked-rotor Test:
V1 = 25 V
f = 15 Hz
I = 27.9 A
Pin = 920 W
(a) Sketch the per-phase equivalent circuit of this motor.
(b) Find the slip at pull-out torque, and find the value of the pull-out torque.