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A 50-hp, 230-V shunt motor has a field resistance of 17.70 and operates at full load when the line current is 181 A at
A 50-hp, 230-V shunt motor has a field resistance of 17.70 and operates at full load when the line current is 181 A at 1,350 r/min. To increase the speed of the motor to 1,600 r/min, a resistance of 5.30 is "cut in" via the field rheostat; the line current then increases to 190 A. Calculate a. The power loss in the field and its percentage of the total power input for the 1,350 r/min speed. b. The power losses in the field and the field rheostat for the 1,600 r/min speed. c. The percent losses in the field and in the field rheostat at 1,600 r/min. A motor with polar moment of inertia J develops torque according to the relationship T = aw+b. The motor drives a load defined by the torque-speed relationship TL = cw2? + d.If the four coefficients are all positive constants, determine the equilibrium speeds of the motor-load pair, and whether these speeds are stable. Assume that a motor has known friction and windage losses described by the equation Tfw= bw. Sketch the T-w characteristic of the motor if the load torque TL is constant, and the TL-w characteristic if the motor torque is constant. Assume that TFWat full speed is equal to 30 percent of the load torque. Develop a Simulink simulator for the shunt-connected DC motor of Problem 14.38. Assume the following parameter values: La = 0.15 H; Lf=0.05 H; Ra = 1.8 Q; Rf = 0.20; ka = 0.8 V-s/rad; kT = 20 N-m/A; kf= 0.20 Wb/A; b=0.1 N-m-s/rad; J = 1 kg-m2.
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