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//Chapter 5:DC Motor Drives
//Example 2
clc;
//Variable Initialization
V1=220 //rated voltage in V
Ia1=100 //rated current in A
N1=1000 //rated speed in rpm clockwise
Ra=0.05 //armature resistance in ohms
Rs=0.05 //field resistance in ohms
//Solution
//Turns is reduced to 80% then flux is also reduced by the same value and hence current is also reduced
T1=Ia1**2 //flux is directly proportional to current Ia
T2=0.8*1**2 //flux is directly proportional to current Ia
Ia2=-Ia1/sqrt(0.8) //since T1=T2 and the direction is opposite
E1=V1-Ia1*(Ra+Rs)
Rs=.8*Rs //Rs=80% of the field resistance 0.05ohm since the flux is reduced to 80%
E2=-(V1+Ia2*(Ra+Rs))
N2=(E2/E1)*(Ia1/Ia2)*(N1/0.8) //since E=Kn*flux*N
//Result
mprintf("\nMotor speed is:N2=%.1f rpm",N2)
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