Help answer part c$),$ the correct answer is $3910$ Nm

Question $3$

Draw the electrical circuit for a dc series motor. Explain in terms of the speed$-$torque characteristic why a belt drive is unsuitable for a series motor.

$[6$ marks$]$

A $\backslash (100\backslash$mathrm$\{$~kW$\},600\backslash$mathrm$\{$~V$\},400\backslash$mathrm$\{$rpm$\}\backslash )$ dc series wound motor in a light transit tram has a combined field and armature resistance of $\backslash (0\mathrm{.}165\backslash$Omega $\backslash ).$ The magnetizing curve at $400$ rpm is as follows:

$($a$)$ Find the rated armature current of this machine;

$($b$)$ Draw the flux $(\backslash ($ k $\backslash$phi $\backslash ))$ field current curve;

$($c$)$ Determine the initial starting torque when the starting current is limited to $340$ A $.$

$[4$ marks$]$