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The power rating of a motor can be modified to account for different ambient temperature, according to the following table: Ambient 30 35 C 40 C temperature C Variation of rated +8% +5% 0 power Ambient 45-C 503 0 55 C temperature Variation of rated -5% -12.5% -25%% power A motor with Pe = 10 KW is rated up to 85:C. Find the actual power for each of the following conditions: a. Ambient temperature is 50 0. b. Ambient temperature is 30 0.A shunt DC motor has a shunt field resistance of 4000 and an armature resistance of 0.20. The motor nameplate rating values are 440 V. 1,200 m/min. 100 hp, and full-load efficiency of 90 percent. Find a. The motor line current. b. The field and armature currents. c. The counter emf at rated speed. d. The output torque.A 240-V series motor has an armature resistance of 0.42 0 and a series-field resistance of 0.18 Q. If the speed is 500 n/min when the current is 36 A, what will be the motor speed when the load reduces the line current to 21 A? (Assume a 3-V brush drop and that the flux is proportional to the current.)A 220-V DC shunt motor has an armature resistance of 0.20 and a rated armature current of 50 A. Find a. The voltage generated in the armature. b. The power developed.A 230-V DC shunt motor has the following parameters: Ra = 0.5 0 Rf= 75 0 Prot = 500 W at 1,120 n/min When loaded, the motor draws 46 A from the line. Find a. The speed, Pdev, and Tsh. b. If Lf= 25 H, La = 0.008 H, and the terminal voltage has a 115-V change, find a(t) and cum(().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 w/min. To increase the speed of the motor to 1,800 /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 /min speed. b. The power losses in the field and the field rheostat for the 1,800 r/min speed. c. The percent losses in the field and in the field rheostat at 1,500 rimin.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 = co2? + 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 Ti = bw. Sketch the T-w characteristic of the motor if the load torque 7L 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.A PM DC motor with torque constant kPM is used to power a hydraulic pump: the pump is a positive displacement type and generates a flow proportional to the pump velocity: qp = kpw The fluid travels through a conduit of negligible resistance: an accumulator is included to smooth out the pulsations of the pump. A hydraulic load (modeled by a fluid resistance R) is connected between the pipe and a reservoir (assumed at zero pressure). Sketch the motor-pump circuit. Derive the dynamic equations for the system, and determine the transfer function between motor voltage and the pressure across the load.A shunt motor in Figure P14.30 is characterized by a field coefficient kf = 0.12 V-s/A-rad, such that the back emf is given by the expression Eb = kilfw and the motor torque by the expression T = kfifla. The motor drives an inertia/viscous friction load with parameters = 0.8 kg-m2 and b = 0.6 N-m-s/rad. The field equation may be approximated by VS = Riff. The armature resistance is Ra = 0.75 0, and the field resistance is Rf= 60 0. The system is perturbed around the nominal operating point VS0 = 150 V, w/0 = 200 rad/s, /80 = 188.67 A, respectively. a. Derive the dynamic system equations in symbolic form. b. Linearize the equations you obtained in part a. Ia Figure P14.30\fThe speed-torque characteristic of an induction motor has been empirically determined as follows: Speed. 1,410 1,470 1,440 1,100 m/min 1,300 Torque, 3 15 N-m 13 Speed, rimin 900 750 350 Torque, N-m 13 11 7 5 The motor will drive a load requiring a starting torque of 4 N-m and increase linearly with speed to 8 N-m at 1,500 w/min. a. Find the steady-state operating point of the motor. b. Equation 14.82 predicts that the motor speed can be regulated in the face of changes in load torque by adjusting the stator voltage. Find the change in voltage required to maintain the speed at the operating point of part a if the load torque increases to 10 N-m.\fCalculate the force exerted by each conductor, 6 in long, on the armature of a DC motor when it carries a current of 90 A and lies in a field the density of which is 5.2 x 10-4 Wb/in2.A 120-V. 10-A shunt generator has an armature resistance of 0.600. The shunt field current is 2 A. Determine the voltage regulation of the generator.A 20-KW. 230-V separately excited generator has an armature resistance of 0.20 and a load current of 100 A. Find a. The generated voltage when the terminal voltage is 230 V. b. The output power.A self-excited DC shunt generator is delivering 20 A to a 100-V line when it is driven at 200 rad/s. The magnetization characteristic is shown in Figure P14.11. It is known that Ra = 1.00 and RF 1000. When the generator is disconnected from the line, the drive motor speeds up to 220 rad/s. What is the terminal voltage? EVA 120 1 = 200 raid/'s 0.5 1.0 1.5 I Amperes Figure P14.11A high-pressure supply and a hydraulic motor are used as a prime mover to generate electricity through a DO generator. The system diagram is sketched in Figure P14.12. Assume that an ideal pressure source, PS, is available, and that a hydraulic motor is connected to it through a linear "fluid resistor," used to regulate the average flow rate. An accumulator is inserted just upstream of the hydraulic motor to smooth pressure pulsations. The combined inertia of the hydraulic motor and of the DC generator is represented by the parameter, J. The DO generator is of the permanent-magnet type, and has armature constants ka = KT. The permanent-magnet flux iso. Assume a resistive load for the generator RL. a. Derive the system differential equations. b. Compute the transfer function of the system from supply pressure, PS to load voltage, VL. R. L T + + D E. R, Figure P14.12A 220-V shunt motor has an armature resistance of 0.320 and a field resistance of 110 0. At no load the armature current is 8 A and the speed is 1,800 n/min. Assume that the flux does not vary with load, and calculate a. The speed of the motor when the line current is 62 A (assume a 2-V brush drop). b. The speed regulation of the motor.A 50-hp, 550-V shunt motor has an armature resistance, including brushes, of 0.36 0. When operating at rated load and speed, the armature takes 75 A. What resistance should be inserted in the armature circuit to obtain a 20 percent speed reduction when the motor is developing 70 percent of rated torque? Assume that there is no flux change
