Q1. Choose the correct answer:1- The disadvantage of starting an induction motor with a star-delta starter is.(a) the starting torque is one-third of the torque in case of delta connection(b) during starting high losses result (c) the starting torque increases and the motor runs withvibration (d) the starting current is high2- In the 3-phase induction motor, the resultant flux of rotating magnetic field is equal to.(a) the maximum value of flux due to any phase(b) 3/2 times maximum value of flux due to any phase(c) 1/2 times maximum value of flux due to any phase(d) 3 times maximum value of flux due to any phase3- If an induction machine is run at speed above the synchronous speed it works inof torque-speed characteristic.(a) induction generator (b) induction motor (c) brake (d) unstable4- The rotor slots are slightly skewed in squirrel cage induction motor to ..............(a) provide ease of fabrication(c) increase the strength of rotor bars5- Crawling in an induction motor is caused by***********........ region(b) reduce the magnetic hum and locking tendency of rotor(d) decrease the amount of copper to be used(d) overheating(a) harmonics (b) low voltage (c) high voltage6- In the 3-phase induction motor, the external type of braking is(a) DC braking (b) plugging (c) mechanical braking (d) AC braking7- The highest starting torque in three phase squirrel cagetype NEMA(a) Design A(b) Design B8- The speed control method type(a) pole changing(d) variable frequency variable voltage control9- The iron losses is represented in the equivalent circuit of three-phase induction motor by(c) Rc (d) RL(a) R1(b) R2***********10-If supply voltage of a 3-phase induction motor is increased 2 times, then torque is(a) increased 2 times (b) decreased 2 times (c) increased 4 times (d) decreased 4 timesinduction motor is found in motor(c) Design C (d) Design D-------------- cannot be applied on wound rotor induction motor.(c) rotor resistance controf(b) stator voltage control-********

Q1. Choose the correct answer: 1- The disadvantage of starting an induction motor with a star-delta starter is (a) the starting torque is one-third of the torque in case of delta connection (b) during starting high losses result (c) the starting torque increases and the motor runs with vibration (d) the starting current is high

Q1. Choose the correct answer: 1- The disadvantage of starting an induction motor with a star-delta starter is (a) the starting torque is one-third of the torque in case of delta connection (b) during starting high losses result (c) the starting torque increases and the motor runs with vibration (d) the starting current is high

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 4-pole, 3-phase, 50Hz induction motor has a voltage between slip-rings on open circuit of 520V. The star connected rotor has a standstill reactance and resistance of 2.0 and 0.4 Ω per phase respectively. Determine: (a) The full-load torque if full load speed is 1,425 rpm(b) The ratio of starting torque to full-load torque(c) The additional rotor resistance required to give maximum torque at standstill.
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 rated load, and the rotor current at starting (as a percentage of the rotor current at rated load). The slip at maximum torque is 0.343 if that helps.
Q2. a) Why the slip of induction motor is never zero, b) What happens if the slip of induction motor is one, c)What is the value of the slip for an induction motor at no load and full load.
Three-phase induction motor, 460 V 50 Hz, 4 poles, 50 hp with Delta, operating at 3.8% slip rated torque when receives Line Voltage 460 V, 50 Hz The parameters of the equivalent circuit per phase are as follows.R1 = 0.33, X1 = X2 = 0.42 and Xm = 30 Ohm / phase.Answer the following questions by neglecting the mechanical losses, Core losses and Stray load losses.A) Value of the rotor resistance R2 B) Maximum torque and rated speed C) line current and starting torque of motor
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, 50Hz, 6-pole squirrel cage induction motor runs at 960-rpm on full load. The stand still rotor resistance and reactance per phase are 0.01 ohm and 0.05 ohm respectively. Express the maximum torque developed in terms of full load toque. Find the slip at which the maximum torque occurs.
1. What is the formula for torque production in a single-phase induction motor? Draw a vector diagram for capacitor start single-phase induction motor.2. Which type of starter is popular for using in induction motor and why?
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?
Q2. For a 10 kW, 380V, three-phase, four-pole, 1200 r/min, delta-connected induction motor. Adopt a specific magnetic loading of 0.4712 Wb/m2 and a specific electric loading of 23000 ampere-conductors per metre. The motor has a full-load efficiency of 85% and a full-load power factor of 0.8. A square pole design may be assumed and the stator leakage impedance voltage drop may be ignored. Assume also that the winding is full-pitched and uniformly wound. To calculate the following design parameters (a) The approximate outer diameter and length of the rotor core (b) the air gap length of the motor (c) the turns per phase (d) the number of conductors per slot, if 3 slots per pole per phase are chosen
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 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.
5.a. A motor which is designed with nonstandard operating characteristics is classified as aA. definite-purpose motor.B. special-purpose motor.C. general-purpose motor. 5.B. For a repulsion motor with bmshes set in the neutral position, what type of winding is needed to producestarting torque?A. A capacitor-phase windingB. A squirrel-cage windingC. A starting winding