A 60 kW, 320 V, 50 Hz, 6 poles, 974 rpm, Y-connected squirrel cage induction motor has following parameters referred to the stator: R, 2. Motor speed is controlled by stator frequency control. The torque equation of the blower is given by TL = 0.0037 w?. 0.05 N, R, 0.04 N, X, = X, = 0.1 1- Calculate: • The current at 50 Hz. A Z • The torque at f Hz. T = N.m 2- If the frequency is decreased to 25 Hz, calculate: • The motor speed N RPM • The starting current I2 = AZ

A 60 kW, 320 V, 50 Hz, 6 poles, 974 rpm, Y-connected squirrel cage induction motor has following parameters referred to the stator: R, 2. Motor speed is controlled by stator frequency control. The torque equation of the blower is given by TL = 0.0037 w?. 0.05 N, R, 0.04 N, X, = X, = 0.1 1- Calculate: • The current at 50 Hz. A Z • The torque at f Hz. T = N.m 2- If the frequency is decreased to 25 Hz, calculate: • The motor speed N RPM • The starting current I2 = AZ

Introductory Circuit Analysis (13th Edition)

13th Edition

ISBN:9780133923605

Author:Robert L. Boylestad

Publisher:Robert L. Boylestad

Chapter1: Introduction

Section: Chapter Questions

Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...

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An induction motor of 30 HP, 220 V, 450% of the rated current with therated voltage and delivers during the starting period, with 130 % of the normal torque. The full load efficiency and full load power factor of the motor is 80 and 70 percent, respectively. If an autotransformer is used as a starting unit and the starting torque of the load is only 50 % of the rated torque of the motor, Determine the starting voltage and the starting current of the line.
The equivalent circuit parameters of a 230-V, 1-phase, 6-pole, 60-Hz induction motor are: R1 = R2’ =10ohm, X1 = X2’ = 10ohm, and Xm = 100ohm. At a slip of 5%, calculate the developed torque and The input power to the motor at 230V, while running on no-load, is 31.4 W at 1.2 A. What is the approximate efficiency of the motor at 5% slip?
Q1) A 4-pole, separately excited, wave wound DC machine with 0.12 armature resistance is rated for 230 V and 5 kW at a speed of 1200 rpm. If the same armature coils are reconnected to forms a lap winding, what is the power (in kW) at 1200 rpm of the reconnected machine if the field circuit is left unchanged? Also voltage regulation in both cases
An 8 pole,40-hp,2300 v,50-Hz, 3 phase, induction motor is operating at 80% of rated load and 6% reduced voltage. The efficiency and power factors for these conditions are 85 and 90 percent respectively. The mechanical power losses, rotor conductor losses, and stator losses are 1011 W, 969 W, and 1559 W respectively.Sketch the power flow diagram and determine:i. Mechanical power developedii. Shaft speediii. Developed torqueiv. Shaft torquev. Slip speedvi. Line current
Q1) A 4-pole, separately excited, wave wound DC machine with 0.12 armature resistance is rated for 230 V and 5 kW at a speed of 1200 rpm. If the same armature coils are reconnected to forms a lap winding, what is the power (in kW) at 1200 rpm of the reconnected machine if the field circuit is left unchanged? Also calculate the voltage regulation in both cases
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The equivalent circuit parameters of a 230-V, 1-phase, 6-pole, 60-Hz induction motor are: R1 = R2’ =10 ohms, X1 = X2’ = 10 ohms, and Xm = 100 ohms. At a slip of 5%, calculate (a) motor speed, (b) input current, (c)power factor, (d) developed torque. (e) at 230V, while running on no-load, is 31.4 W at 1.2 A.What is the approximate efficiency of the motor at 5% slip?
A 40 hp, 230-V, 8 pole , 25-Hz three phase induction motor is running at 355 rpm at rated load. The torque lost by friction is 24 N-m. If total stator losses amount to 1000 W, evaluate the efficiency of the motor at this load.
3. A dc shunt motor operating unloaded at a terminal voltage of 125V at a speed of 1420 rpm. When themotor is operated unloaded at the same terminal voltage but with an additional resistance of 8Ω in serieswith the shunt field, the motor speed is 1560rpm. (Ignore armature reaction and magnetic saturation)a) Calculate the resistance of the shunt field.b) Calculate the motor speed if the series resistance is increased from 8Ω to20Ω. c) With the field resistance at its original value and no series resistance, calculate the motor speed if it isoperated loaded at a terminal voltage of 90 V and a terminal current of 100A.
A four-pole, three-phase induction motor rotatesat 1,700 r/min when the load is 100 N-m. The motoris 88 percent efficient.a. Determine the slip at this operating condition.b. For a constant-power, 10-kW load, determine theoperating speed of the machine.c. Sketch the motor and load torque–speed curves onthe same graph. Show numerical values.d. What is the total power consumed by themotor?
The armature, series field and shunt field resistances of a 125kW, 250V long shunt cumulative compound dc generator are 0.025-ohm, 0.01 ohm and 30 ohms, respectively. If the stray power loss at rated load is 5kW, determine the motor brake horsepower required to drive this machine. Assume a brush drop of 2V and a stray load loss of 1% of the output.
A 4-pole, 115 V, 60 Hz, 1710 rpm, capacitor-start single-phase induction motor has been designed to produce maximum starting torque per unit starting current. The motor has the following parameters: R1m=1.5ohms, X1m=2.6ohms, R1a=2.5 ohms, X1a=2.5 ohms, Xmag=40 ohms, R/2=1 ohms, X/2=1.6 ohmsNa/Nm =l, Capacitor in series with auxiliary winding = 375 μF.a) Draw the equivalent circuit for the motor under starting conditions. Determine the value of the starting torque.b) Draw the equivalent circuit for the motor when it runs at the rated (i.e., full load) speed. Determine the torque developed at this speed.c) Determine the ratio of the starting torque to the torque developed at the rated speed.