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 100kW, 600V, 400rpm dc series wound motor in a light transit tram has a combined field and armature resistance of 0.165 Q. The magnetizing curve at 400rpm is as follows: Ea,[V] If, [A] 375 169 400 425 450 475 194 225 261 300 (a) Find the rated armature current of this machine; (b) Draw the flux (ko) field current curve; [4 marks] [6 marks] (c) Determine the initial starting torque when the starting current is limited to 340A. [4 marks]