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//Chapter 5:Dc Motor Drives
//Example 13
clc;
//Variable Initialization
//Ratings of the separately excited motor
V=200 // rated voltage in V
N=875 // rated speed in rpm
Ia=150 // rated current in A
Ra=0.06 // armature resistance in ohms
Vs=220 // source voltage in V
f=50 // frequency of the source voltage in Hz
//Solution
E=V-Ia*Ra //back emf
Vm=sqrt(2)*Vs //peak voltage
//(i)When the speed is 750 rpm and at rated torque
N1=750 //given speed in rpm
E1=N1/N*E //back emf at the given speed N1
Va=E1+Ia*Ra //terminal voltage
cos_alpha=Va*%pi/2/Vm
alpha=acos(cos_alpha) //required firing angle in radian
alpha1=alpha*180/%pi //required firing angle in degrees
//(ii)When the speed is -500rpm and at rated torque
N1=-500 //given speed in rpm
E1=N1/N*E //back emf at the given speed N1
Va=E1+Ia*Ra //terminal voltage
cos_alpha=Va*%pi/2/Vm
alpha=acos(cos_alpha) //required firing angle in radian
alpha2=alpha*180/%pi //required firing angle in degrees
//(iii)When the firing angle is 160 degrees
alpha=160 //firing angle in degrees
alpha=alpha*%pi/180
Va=2*Vm/%pi*cos(alpha)
E1=Va-Ia*Ra //since Va=E1+Ia*Ra
N1=E1/E*N //the required speed at the given firing angle
//Results
mprintf("(i)Hence the required firing angle is :%.1f °",alpha1)
mprintf("\n(ii)Hence the required firing angle is :%.1f °",alpha2)
mprintf("\n(iii)Hence the required speed is :%.1f rpm",N1)
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