Exam Electrical Engineering

$2\mathrm{.}10\mathrm{.}2020$

Task $1$

$(20$ points$)$

A shunt connected $250$ V DC motor has a armature winding of a $4-$pole. The armature is lap connected. There are $60$ slots, each of which contains $16$ conductors. The flux per pole is $20$ mWb $.$ The total current supplied to the motor is $25$ A $.$ The resistance of armature and field circuit are $0\mathrm{.}1$ and $125$ respectively. The friction$-$related losses at the shaft amount to be $810$W$.$

$($i$)$ Draw the equivalent circuit for this motor.

$(2$ pts$)$

$($ii$)$ Calculate

$($a$)$ Armature current and the rotational speed of the motor;

$(3$ pts$)$

$($b$)$ Gross torque;

$(5$ pts $)$

$($c$)$ Useful torque; and

$(5$ pts $)$

$($d$)$ Efficiency

$(5$ pts$)$Exam Electrical Engineering

$2\mathrm{.}10\mathrm{.}2020$

Task $1$

$(20$ points$)$

A shunt connected $250$ V DC motor has a armature winding of a $4-$pole. The armature is lap connected. There are $60$ slots, each of which contains $16$ conductors. The flux per pole is $20$ mWb $.$ The total current supplied to the motor is $25$ A $.$ The resistance of armature and field circuit are $0\mathrm{.}1$ and $125$ respectively. The friction$-$related losses at the shaft amount to be $810$W$.$

$($i$)$ Draw the equivalent circuit for this motor.

$(2$ pts$)$

$($ii$)$ Calculate

$($a$)$ Armature current and the rotational speed of the motor;

$(3$ pts$)$

$($b$)$ Gross torque;

$(5$ pts $)$

$($c$)$ Useful torque; and

$(5$ pts $)$

$($d$)$ Efficiency

$(5$ pts$)$