Three phase induction motors run at constant speed from zero to full load, which can stabilize the movement at the interface of the application. (a) How can the induction motor runs with a constant speed from zero to full load? Explain this behavior using its torque-speed curve. (b) A 460V, 4-pole, 75-hp, 60 Hz, Y-connected, three phase induction motor has full-load torque at 3.5% slip when operating at the rated condition. The per-phase circuit model impedances of the motor are: R = 0.0580 Хм — 180 х,%3D0.320 Х, 3 0.3860 All losses maybe neglected in this problem. (i) Compute the voltage and impedance for the Thevenin equivalent circuit for this motor. (ii) How much torque is induced in this motor when operating at the rated condition? (iii) What is the value of rotor resistance, R2? (iv) What is the slip and the corresponding rotor speed at the pullout torque of the motor?

Three phase induction motors run at constant speed from zero to full load, which can stabilize the movement at the interface of the application. (a) How can the induction motor runs with a constant speed from zero to full load? Explain this behavior using its torque-speed curve. (b) A 460V, 4-pole, 75-hp, 60 Hz, Y-connected, three phase induction motor has full-load torque at 3.5% slip when operating at the rated condition. The per-phase circuit model impedances of the motor are: R = 0.0580 Хм — 180 х,%3D0.320 Х, 3 0.3860 All losses maybe neglected in this problem. (i) Compute the voltage and impedance for the Thevenin equivalent circuit for this motor. (ii) How much torque is induced in this motor when operating at the rated condition? (iii) What is the value of rotor resistance, R2? (iv) What is the slip and the corresponding rotor speed at the pullout torque of the motor?

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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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 three phase, 4 pole, 3300 V, 50 Hz, star connected Induction motor, has identical primary and referred secondary impedance of value 3+j9 Ohm per phase. Using the approximate circuit, calculate: A. The full load torque at rated slip of 5%. B. The maximum torque at normal voltage and frequency.
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.
A 3-phase, 6-pole induction motor is rated 400Hz, 150V, 10hp, 3% slip at rated power output. The windage and friction loss is 200W at rated speed. With the motor operating at rated voltage, frequency, slip, and power output, determine the output torque.
A 3300-V, 50-Hz, 3-phase, 4-pole, star-connected induction motor has identical primary and referred secondary impedances of value 3 + j9 ohm per phase. The turns-ratio per phase is 3/I (stator/rotor), and the rotor winding is connected in delta and brought out to slip rings. Calculate: the full-load torque at rated slip of 5%; the maximum torque at normal voltage and frequency; the supply voltage reduction which can be withstood without the motor stalling; the maximum torque if the supply voltage and frequency both fall to half normal value; the increase in rotor-circuit resistance which, at normal voltage and frequency, will permit maximum torque to be developed at starting. Express this: as a fraction of normal R2and as (3) ohmic values to be placed in series with each of the slip-ring terminals and star connected.
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 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 75kW, 440V, 3-phase, 6-pole,50Hz wound rotor induction motor has a full load slip of0.04 and the slip at maximum torque of 0.2 when operating at rated voltage and frequencywith rotor winding short circuited at the slip rings. Assume the stator resistance androtational losses to be negligible. Find(a) Maximum torque(b) Starting torque(c) Full load copper loss.The rotor resistance is now doubled by adding an external series resistance.Determine(d) Slip at full load(e) full-load torque(f) slip at maximum torque
A three-phase, star connected, 50Hz, 4-pole, 380V, 15HP asynchronous motor rotating at 1404 rpm below has one phase equivalent circuit parameters. The friction and wind losses of this motor are 250W. A phase equivalent circuit is simplified by taking the magnetic circuit in front of the stator circuit. Accordingly, find the slip where the maximum torque occurs, the maximum torque, the slip where the maximum power occurs, the maximum power and the development current. (Rs = 0.15Ω, R′r = 0.18Ω, Xs = 0.31Ω, X′r = 0.31Ω, Vs = 220V)
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.
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?
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?