Q2 (a) A new glue manufacturer is decided to have an adhesive mixer machine. Describe in brief the suitable motor for this application with appropriate justification. Sketch the torque-speed characteristics curve for this load. (5 marks) (b) A 440 V, two-pole, 50 Hz, Y-connected induction motor is used as a pump in an industrial plant. It has an inductive reactance of 3 2 and a stator resistance of 0.4 2. The rotor resistance referred to the stator is 0.25 12. The motor is driving a constant-torque load of 80 Nm at operating slip of 3.25%. The braking system of this motor is utilising the Fixed Width Modulation based dynamic braking technique. The duty ratio is taken as 20%. The motor is driven by a six-step converter with DC link voltage of 250 VDC. (i) If the motor speed is controlled via frequency, point out the motor current at rated frequency and at the maximum frequency. (6 marks) (ii) Analyse the motor speed at rated frequency and at the maximum frequency for the case in Q2(b)(i). (2 marks) (iii) Determine the braking current required for this motor. (2 marks) (iv) Analyse the starting current of this motor at rated frequency and at the maximum frequency (2 marks) (v) Propose a better method so that the starting current is remained at minimum value. Demonstrate the method. (3 marks) Grid system Tx Lump Load, L1 650 kW +820 kVAr Lump Load, L3 950 kVAr PF = 0.76 lagging M Lump Load, L2 500 kW PF = 0.82 lagging 1250 hp Starting current = 6.5 X PF =0.85 lagging, Efficiency = 96% Figure Q1(b) Appendix A Table A1 M.D ranges of individual consumer Up to 12 kVA > 12 kVA to 100 kVA (Non Domestic) Up to 100 kVA (Domestic) > 100 kVA to 350 kVA > 350 KVA to 12 kVA to 100 kVA (Non Domestic) Up to 100 kVA (Domestic) > 100 kVA to 350 kVA > 350 KVA to