7.The rotor resistances per phase of a 4-pole, 50-Hz, 3-phase induction motor are 0.024 ohm and 0.12ohm respectively. Find the speed at maximum torque. Also find the value of the additional rotorresistance per phase required to develop 80% of maximum torque at starting.[1200 r.p.m. 0.036 Q] (Elect. Machines, A.M.I.E. Sec. B, 1990)8.The resistance and reactance per phase of the rotor of a 3-phase induction motor are 0.6 ohm and5 ohms respectively. The induction motor has a star-connected rotor and when the stator isconnected to a supply of normal voltage, the induced e.m.f. between the slip rings at standstill is 80V. Calculate the current in each phase and the power factor at starting when (i) the slip-rings areshorted, (ii) slip-rings are connected to a star-connected resistance of 4 ohm per phase.[(i) 9.17 amp, 0.1194 lag (i) 6.8 amp, 0.6765 lag||Rajiv Gandhi Technical University, Bhopal, 2000]

7. The rotor resistances per phase of a 4-pole, 50-Hz, 3-phase induction motor are 0.024 ohm and 0.12 ohm respectively. Find the speed at maximum torque. Also find the value of the additional rotor resistance per phase required to develop 80% of maximum torque at starting. [1200 r.p.m. 0.036 2] (Elect. Machines, A.M.I.E. Sec. B, 1990) 8. The resistance and reactance per pbase of the rotor of a 3-phase induction motor are 0.6 ohm and

7. The rotor resistances per phase of a 4-pole, 50-Hz, 3-phase induction motor are 0.024 ohm and 0.12 ohm respectively. Find the speed at maximum torque. Also find the value of the additional rotor resistance per phase required to develop 80% of maximum torque at starting. [1200 r.p.m. 0.036 2] (Elect. Machines, A.M.I.E. Sec. B, 1990) 8. The resistance and reactance per pbase of the rotor of a 3-phase induction motor are 0.6 ohm and

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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Similar questions

A three-phase induction motor, operating at rated voltage and frequency, has a startingtorque of 1.35 times and a maximum torque of 2.2 times, both with respect to its rated-loadtorque. Ignoring the effects of the stator resistance and rotational losses and assumingconstant rotor resistance, determine the slip at the maximum torque;
a. A three-phase, 220-V, 60-Hz induction motor runsat 1,140 r/min. Determine the number of poles (forminimum slip), the slip, and the frequency of therotor currents.b. To reduce the starting current, a three-phasesquirrel cage induction motor is started byreducing the line voltage to Vs/2. By what factorare the starting torque and the starting currentreduced?
A three-phase 60 Hz induction motor connected to a three-phase bus at rated voltage isoperating at a low slip condition (i.e s < 20%) resulting in a steady state speed of 1090 rpm.(a) How many poles does the motor have?(b) What is the percentage slip at the operating speed?(c) What is the corresponding frequency, (fr) of the currents and voltages induced in therotor winding?
A 6-pole, 60-Hz, Y-connected, three-phase induction motor develops a torque (Td) of 250 N.m at a speed of 720 rpm. The rotor resistance is 0.4 Ohm/phase, and the stator winding impedance is negligible. A) What is the air-gap power? B) What is the rotor current refered to the stator? C) If the rotational loss is 1kW, what is the motor output power in hp?
The rotor resistance and reactance per phase of a 4-pole, 50-Hz, 3-phase induction motor are 0.025 ohm and 0.12 ohm respectively. Make simplifying assumptions, state them and : (i) find speed at maximum torque (ii) find value of additional rotor resistance per phase required to give three-fourth of maximum torque at starting. Draw the equivalent circuit of a single-phase induction motor.
A 80 kW, 480-V, 60-Hz, six pole induction motor has a slip of 5 percent when operating at fullload conditions. At full-load conditions, the friction and windage losses are 300 W, and the core losses are 400 W. For full-load conditions, compute the induced torque,T-ind, in N-m.
A 480 V, 2-poles, 60 Hz, Y-connected induction motor has an inductive reactance of 4ohm and the resistance of R, = 0.2ohm and R', 0.3ohm. The motor is driving a constant-torque load of 150 Nm at a speed of 3500 rpm. Assume that this torque includes the rotational components. Calculate the motor speed and starting current if the frequency is decreased to 50 Hz.
A 6-pole, 50 Hz, 3-phase induction motor runs at 960 rpm while delivering a shaft torque of 120 N-m. If friction and windage loss amount to 180 W., determine the rotor copper loss.
A three-phase induction motor, at rated voltageand frequency, has a starting torque of 140 percentand a maximum torque of 210 percent of full-loadtorque. Neglect stator resistance and rotational lossesand assume constant rotor resistance. Determinea. The slip at full load.b. The slip at maximum torque.c. The rotor current at starting as a percentage offull-load rotor current.
The full load slip of a 4-pole, 60Hz, 440V (line-to-line) three phase induction motor is 0.05. (i). What is the speed of the rotating stating? What is the frequency (in Hz) of the rotor current? (ii). When the output power of the motor is 90 hp at a speed of 1732 rmp, rotational losses (which include frictional and core losses) are 10,100W, while copper losses for both the rotor and stator total 3700W. Determine the motor efficiency and line current, assuming the motor has a 0.8pf lagging under the conditions.
A 50-kW, 440-V, 50-Hz, six-pole induction motor has a slip of 6 percent when operating at full-load conditions. At full-load conditions, the friction and windage losses are 300 W, and the core losses are 600 W. Find the following values for full-load conditions: (a) The shaft speed nm (b) The output power in watts (c) The load torque load in newton-meters (d) The induced torque ind in newton-meters (e) The rotor frequency in hertz
A series dc motor 20-hp, 500-V, is having armature, series field and shunt field winding resistances of 0.08 Ω, 0.3 Ω and 125 Ω, respectively. If the back – emf is 478 V, determine the motor current when the connection is a) long – shunt. b) short – shunt c) series d) shunt