Electrical Machines and Drives | Assignment

Electrical Machines and Drives
Solution 1:
Separately Excited DC Motor
Parameters :
Voltage = 500 V , 100 hp, 2500 r / min
Field Resistance = Rf = 109 Ohm
Rated field voltage = Vf0 = 300 V
Armature Resistance = Ra = 0.084 Ohm
Geometric constant = kf = 0.694 V / ( A rad / s )
Case 1 : Motor operating under no load
Vf = If Rf
Armature circuit :
Va = Ia Ra + Eg = Ia Ra + Kv . w . If
Back emf = Eg = Kv . w . If

W = Vs – Va / kv * If
If = Vf / Rf
Torque = k * Ia
Td = kt * If * ia
W = 500 – Va / ( 0.694 * 300 / 109 )
At constant field voltage = 300 V
Plot of motor speed versus the armature voltage ( as the armature voltage is varied from 250
V to 500 V ) using MATLAB software :
MATLAB Code :
V = 250 : 1 : 500 ;
w = ( 500 – V ) / ( 0.694 * 300 / 109 ) ;
plot ( V , w ) ;
xlabel ( ' Armature voltage ' ) ;
ylabel ( ' Motor Speed ' ) ;

Figure 1
Case 2 : Motor operating under rated full load torque
Plot of motor speed versus the armature voltage ( as the armature voltage is varied from 250
V to 500 V ) using MATLAB software :
MATLAB Code :
Va = 250 : 1 : 500 ;
W1 = ( 500 – Va ) / ( 0.694 * 300 / 109 ) ;
plot ( Va , w1 ) ;
xlabel ( ' Armature voltage ' ) ;
ylabel ( ' Motor Speed ' ) ;