Design of DC Motor Starter A starter circuit is to be designed for a shunt motor

Question

Design of DC Motor Starter A starter circuit is to be designed for a shunt motor rated at 30hp, 400V, and 75A. Its armature resistance is (0.2+0.00522), and the shunt field resistance is (100+0.2522) . The motor is to be started with no more than (200+0.522 percent of its rated armature current, and as soon as the current falls to rated value a starting resistor stage is to be cut out. Determine how many stages of starting resistance are needed, and how large should each one be?
Write a MatLab program that will calculate and print (a) the required number of stages, and (b) resistance values of each stage (i.e. Rs1, Rs2, ……). Sample output is: Number of stages = 3        [2 Points] Rs1 = 2.218 ohm Rs2 = 0.887 ohm Rs3 = 0.091 ohm.

(only mat lab part is needed)

Explanation / Answer

v = 400; %voltage rating in volts
p = 30*746; %power rating in watts
rf = 100+0.25*22; %field resistance in ohms
ra = 0.2+0.005*22; %armature resistance
If = v/rf; %constant shunt field current = voltage/field resistance
Iar = (p/v)-If; %rated armature current = (power/voltage) - constant shunt field current
Ist = (200+0.5*22)*Iar/100; %starting current = (200+0.5*22)% of rated armature current
Rext = (v/Ist)-ra; %external resistance required at the time of starting
Res = []; %create a blank matrix for the value of exernal resistance
k = 0; %create a counter to show number of stages
for i = 1:20
Ec = v-Iar*(Rext+ra); %counter emf
R = ((v-Ec)/Ist);
Rext_new = R-ra;
new = Rext-Rext_new;
Res = [Res new]; %update the values of matrix for external resistance
Rext = Rext_new; %assign the external resistance to new value
k = k+1; %increase the number of stages by 1
if Rext <= ra %check if all the external resistances are removed
break
end
end
k = k-1;
Res = Res(1:end-1);
disp('The number of stages are = ')
disp(k)
disp('The value of external resistance are = ')
disp(Res)

Related Questions

Navigate

• Browse (All)
• Browse D
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.