Question

Problem 2

Example Motor: 4-pole, 220 V, 60 Hz, 1700 rpm Problem #1: The example motor is inverter driven with its rotor slip frequency controlled so that u, = u,Rated-2094 rad/s. The motor is coupled to a mechanical load with the torque-speed characteristic shown. a) b) For nm-0, find f, l,',VI, and ??. (ans. 3.33, 29.54, 3. I 15,0) For nm-1500 rpm, find f, 12,v,,and ?.(ans . 53.33,72.35, 122.09, 93.75) (N.m) 150 25 n (rpm) 1500 Problem # 2: The inverter driving the motor of Problem #1 is fed from a 6-pulse, phase-controlled converter which is in turn fed from a 240 V (line-to-line) 3-phase source. The filter capacitor is effective in averaging that V(=V. 3-phase 6-pulse Phase controlled | 6-step 3-phase Inverter 240 V Induction Motor converter a) If the inverter is a "120 degree" inverter, find the firing angle of the phase controlled converter SCRs for b) of Problem #1. (ans. 16.19) b) Work part a) for a "180 degree" inverter. (ans. 33.72) Problem #3: The example motor is operated by an inverter maintaining constant rotor slip frequency control. The control system maintainsPa ad V IRael A mechanical load is to be driven at 2000 rpm. The load torque is 100 ?.m. Rated Is it possible to drive the load with f 3.33 Hz? If not, why not? Is it possible to drive the load with f, 4Hz? a) b)

Answer 1

Total z = R times z_L/R + z_L DoubleRightarrow 1000 times 50 angle -100 degree/1000 + 50 angle -100 z = 50.37 angle 82.84 ohm V = I middot z DoubleRightarrow 0.275 angle 20 times 50.37 angle 82.84 v = 13.85 angle 102.84 degree v a) Instataneous power: At source P_L = V_L times I_L = V_m sin (omega t + theta_v) times I_m sin (omega t + theta_i) DoubleRightarrow v_m I_m [sin (omega t + theta_v) sin (omega t + theta i)]