4. The speed of a 50 hz, 4 pole induction motor running with a slip of 54 will be a. 1760 rpm b. 950 rpm c. 1488 rpm d. 1425 rpm 5. A 3-phase induction motor is rated 220 volts and 1745 rpm and 784 power factor. What is the percent slip? (EE board Prob. Oct'97) a. 2.54 b. 3.54 c. 3.14 d. 44 6. A 50 hp three phase motor, rated 220 volts, 75% power factor has 6 poles. The slip at full load is 34. What is the frequency of the rotor current at full load? (EE Board Prob. Mar '98)

4. The speed of a 50 hz, 4 pole induction motor running with a slip of 54 will be a. 1760 rpm b. 950 rpm c. 1488 rpm d. 1425 rpm 5. A 3-phase induction motor is rated 220 volts and 1745 rpm and 784 power factor. What is the percent slip? (EE board Prob. Oct'97) a. 2.54 b. 3.54 c. 3.14 d. 44 6. A 50 hp three phase motor, rated 220 volts, 75% power factor has 6 poles. The slip at full load is 34. What is the frequency of the rotor current at full load? (EE Board Prob. Mar '98)

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 50 HP, 440 volts, 3-phase induction motor delivers during starting period 150% of the normal torque and draws 550% of the rated current with the rated voltage. The full load pf and full load efficiency are 80% and 90% respectively. If the starting torque of the load is only 50% of the rated torque of the motor and an auto transformer is used as starting unit, what should be the starting current at this voltage?A. 125 ampB. 130 ampC. 180 ampD. 254 amp
A 10Hp, 550V, 60Hz, 3-phase induction motor has a starting torque of160% of full load torque and a starting current of 425% of full loadcurrent. If the motor is used on a 440V, 60Hz system, what will be thestarting torque expressed in percent of its full load value?
A 3-phase, 60 Hz, six pole, 220-volt wound rotor induction motor has a stator that is connected in Delta and the rotor that is connected in Wye. The rotor has haft as many turns as that stator. the RR is equal to 0.1- ohm and XBR is equal to 0.5-ohm (a) calculate also the starting torque developed by the motor (b) For over all operation of this induction motor, calculate the efficiency based on the gathered data.
16. A single-phase, 1/4 hp, 230 V, 60 Hz, four-pole, 1710 rpm induction motor has the following equivalent circuit parameters for the main winding: R1m=9.5Ω, R02=10.8Ω, X1m=X/2=12Ω, Xmag=260Ω At 230V and rated speed, the core loss is 30W, and the friction and windage loss is 15W. The motor is connected to an 1 φ, 230V, 60Hz supply and runs at the rated speed. Determine:a) The slip.b) The motor current.c) The input power factor.d) The input power.e) The developed torque.f) The output shaft power and shaft torque.g) The efficiency.h) The rotor circuit frequencies and the rotor cu-losses.i) The ratio of the forward flux to the backward flux.
e specifications of a Y-connected three phase induction motor are as follows: 12-hp, 400-V, 17-A, 0.85-PF, 50-Hz, 1410-rpm, S1, Class E, IP22.(a) How many poles does this motor have?(b) Determine the rated torque and rated efficiency of the motor?
A single phase induction motor is rated 5 hp, 75% power factor and 220 volts. What approximate size of capacitor is necessary to raise the power factor to about 90%?
A four-pole, single-phase, 120 V, 60 Hz induction motor gave the following standstill impedances when tested at rated frequency:Main winding : Zm =1.5+j4 ohmsAuxiliary winding : Za =3+j6 ohmsa) Determine the value of external resistance to be inserted in series with the auxiliary winding to obtain maximum starting torque as a resistor split-phase motor.b) Determine the value of the capacitor to be inserted in series with the auxiliary winding to obtain maximum starting torque as a capacitor-start motor.c) Determine the value of the capacitor to be inserted in series with the auxiliary winding to obtain maximum starting torque per ampere of the starting current as a capacitor-start motor.d) Compare the starting torques and starting currents in parts (a), (b), and (c) expressed as per unit of the starting torque without any external element in the auxiliary circuit, when operated at 120V, 60Hz.
A75 hp, 3-phase, 6-pole, 60 Hz induction motor delivers full load torque at 5% slip. If the load torque is increased by 15% as allowed by the service factor on the nameplate, determine the new speed and horsepower delivered
17. A single-phase, 120 V, 60 Hz, four-pole, split-phase induction motor gave the following blockedrotor test data:VIP Main winding 32 4 80Auxiliary winding 40 4 128a) Determine the standstill impedances of the main and auxiliary windings.b) Determine the values of the resistances to be added in series with the auxiliary winding to obtain maximum starting torque.c) Compare the starting torques and starting currents with and without the added resistance in the auxiliary winding circuit if the motor is connected to a 120 V, 60 Hz supply
21. A) At what percentage of slip is the pull-out or breakdown torque of a typical 3-phase squirrel-cage induction motor reached? a) 3% slip b) 10% slip c) 20% slip d) none of the above B) If load is increased beyond the breakdown torque, what happens to the speed of the motor? a) it stops b) it may speed up beyond its rated rpm c) its speed will not change, but its current will go downd) none of the above
A 3-phase induction motor, 440-V, 50-Hz, 6-pole, delta-connected has the following equivalent-circuit parameters at normal frequency:R1.2 ohm, R'2=0.18 ohm, X1= x'2=0.58 ohm, all per phase values. The machine is subjected in service to an occasional fall of 40% in both voltage and frequency. What total mechanical load torque is it safe to drive so that the machine just does not stall under these conditions? When operating at normal voltage and frequency, calculate the speed when delivering this torque and the power developed. Calculate also the speed at which maximum torque occurs. If V and f were both halved, what would be the increase in starting torque from the normal direct-on-line start at rated voltage and frequency? If now the machine is run up to speed from a variable-voltage, variable-frequency supply, calculate the required terminal voltage and frequency to give the 'safe' torque calculated above: (i) at starting, (ii) at 500 rev/min. Repeat (d) for the machine to develop a…
Question: If a motor driven by PWM using half-bridge operation has a speed of 1422 rpm at a duty cycle of 100% (full forward), what will its speed be at a duty cycle of 63%? Enter your answer to the 2nd nearest decimal place. If rotation direction of the motor is reverse, use negative (-) sign.