Exam Electrical Engineering

$26\mathrm{.}08\mathrm{.}2021$

A shunt$-$connected D$.$C$.$ motor takes an armature current of $100$ A at $300$ V $.$ The armature circuit resistance is $0\mathrm{.}6.$ The machine has $10-$poles and the armature is lap$-$connected with $700$ conductors. The flux per pole is $0\mathrm{.}06Wb.$ Answer the following questions:

$($a$)$ Draw the equivalent circuit representing this motor.

$[2$ pts$]$

$($b$)$ Calculate the speed.

$[5$ pts$]$

$($c$)$ Calculate the gross torque developed by the armature.

$[5$ pts$]$

$($d$)\_$For reducing the speed by $50\%,$ calculate the additional resistance to be inserted in series with the armature if the load torque is to be kept constant;

$[13$ pts$]$