A 220 V, 1500 rpm, 11.6 A (armature current) separately excited motor is controlled by a single phase, full wave SCR converter. The armature resistance of the motor is 2 ohm. The ac source voltage is 230 V (rms) 60 Hz. Enough filtering inductance is added to ensure continuous conduction for any torque greater than 25% of the rated value. You may ignore the rotational losses. What should be the value of the firing angle (triggering angle) to drive a mechanical load of rated torque at 1000 rpm?