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//Chapter 5:Dc Motor Drives
//Example 18
clc;
//Variable Initialization
//The separately excited motor is fed from a circulating dual converter
V=220 // rated voltage in V
N=1500 // rated speed in rpm
Ia=50 // rated current in A
Ra=0.5 // armature resistance in ohms
Vl=165 // line voltage in V
f=50 // frequency of the source voltage in Hz
//Solution
E=V-Ia*Ra //back emf at the rated speed
Vm=Vl*sqrt(2) //peak voltage
//(i)During motoring operation when the speed is 1000 rpm and at rated torque
N1=1000 //speed of the motor in rpm
E1=N1/N*E //back emf at the given speed N1
Va=E1+Ia*Ra //terminal voltage at the given speed N1
alpha_A=acos(%pi/3*Va/Vm)
alpha_A=alpha_A*180/%pi//required converter firing angle in degrees
alpha_B=180-alpha_A
//(ii)During braking operation when the speed is 1000 rpm and at rated torque
N1=1000 //speed of the motor in the book is given as 100 rpm which is wrong
E1=N1/N*E //back emf at the given speed N1
Va=E1-Ia*Ra //terminal voltage at the given speed N1
alpha_A1=acos(%pi/3*Va/Vm)
alpha_A1=alpha_A1*180/%pi//required converter firing angle in degrees
alpha_B1=180-alpha_A1
//(iii)During motoring operation when the speed is -1000 rpm and at rated torque
N1=-1000 //speed of the motor in rpm
E1=N1/N*E //back emf at the given speed N1
Va=E1-Ia*Ra //terminal voltage at the given speed N1
alpha_A2=acos(%pi/3*Va/Vm)
alpha_A2=alpha_A2*180/%pi//required converter firing angle in degrees
alpha_B2=180-alpha_A2
//(iv)During braking operation when the speed is -1000 rpm and at rated torque
N1=-1000 //speed of the motor in the book it is given as 100 rpm which is wrong
E1=N1/N*E //back emf at the given speed N1
Va=E1+Ia*Ra //terminal voltage at the given speed N1
alpha_A3=acos(%pi/3*Va/Vm)
alpha_A3=alpha_A3*180/%pi//required converter firing angle in degrees
alpha_B3=180-alpha_A3
//Results
mprintf("\n(i)Hence the required firing angle is :%.1f °",alpha_B)
mprintf("\n(ii)Hence the required firing angle is :%.1f °",alpha_B1)
mprintf("\n(iii)Hence for negative speed during motoring operation the required firing angles are :")
mprintf("\nalpha_A :%.1f ° and alpha_B :%.1f °",alpha_A2,alpha_B2)
mprintf("\n(iv)Hence for negative speed during braking operation the required firing angles are :")
mprintf("\nalpha_A :%.1f ° and alpha_B :%.1f °",alpha_A3,alpha_B3)
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