Hey guys ![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
I keep getting a different answer to a question. Can anyone explain where I'm going wrong?
Question:
220V DC shunt motor has an armature resistance of 0.2Ω and field resistance of 110Ω. At no-load, the motor runs at 1000rmp, and it draws a line current of 7A. At full-load, the input to the motor is 11kW. Consider the air gap flux remains fixed at its value at no load; that is armature reaction
a) fined Ea, speed and speed regulation at full load
b) Developed torque at full load
c) Starting torque if the starting armature current is limited to 150% of full load current.
Answers:
Ea = 210.4V, N2 = 960.7, %SR = 41%
Pd = 100.4N.m, Tst = 150.6N.m
I can't get the first part...
. Can anyone help me get started?
My attempt
a)
Ra = 0.2, Rf = 110
V = 220
If = V/Rf = 220/110 = 2A
Ia = IL -If = 7A - 2A = 5A
Ea = V - Ia*Ra = 220 - 5*0.2 = 219
...wrong![Frown :( :(](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
thanks guys
I keep getting a different answer to a question. Can anyone explain where I'm going wrong?
Question:
220V DC shunt motor has an armature resistance of 0.2Ω and field resistance of 110Ω. At no-load, the motor runs at 1000rmp, and it draws a line current of 7A. At full-load, the input to the motor is 11kW. Consider the air gap flux remains fixed at its value at no load; that is armature reaction
a) fined Ea, speed and speed regulation at full load
b) Developed torque at full load
c) Starting torque if the starting armature current is limited to 150% of full load current.
Answers:
Ea = 210.4V, N2 = 960.7, %SR = 41%
Pd = 100.4N.m, Tst = 150.6N.m
I can't get the first part...
My attempt
a)
Ra = 0.2, Rf = 110
V = 220
If = V/Rf = 220/110 = 2A
Ia = IL -If = 7A - 2A = 5A
Ea = V - Ia*Ra = 220 - 5*0.2 = 219
...wrong
thanks guys