Q1. A 450 V, 50 Hz, 1450 r.p.m., 25 kW, star-connected three-phase induction motor deliversconstant (rated) torque at all speeds. The motor equivalent circuit parameters at ratedfrequency are R1=0.12, R2 = 0.17 2, X₁ = 0.3 2, X2 = 0.5 2, Xm = 23.6 2. Smooth speedvariation is obtained by primary frequency control with simultaneous variation of the terminalvoltage to maintain constant air-gap flux. Calculate the motor current, power factor andefficiency at one-fifth of rated speed.

Step 1: Understanding the problems and hidden variables:Step 2: Given the motor runs at 1/5th speed,…

Answered: Q1. A 450 V, 50 Hz, 1450 r.p.m., 25 kW,…

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter32: Three-phase Motors

Section: Chapter Questions

Problem 6RQ: Name three factors that determine the torque produced by an induction motor.

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L-1). The 3-phase wound-rotor induction motor has .... . a) high starting torque b) low starting current c) both "a" and "b" d) neither "a" nor "b" L-2). The 3-phase wound-rotor induction.........a) motor has a wire wound rotor b) motor's rotor can be connected to an external resistive load by way of slip rings and brushes c) motor requires more maintenance than the 3-phase squirrel-cage induction motor d) all of the above L-3). The 3-phase wound-rotor induction motor's rotor circuit's resistance should be adjusted so it is__________ during starting. a) low b) high c) either "a" or "b" d) neither "a" nor "b" L-4). Will a 3-phase wound-rotor induction motor start with no external circuit connected to its rotor leads? a) yes b) no
A 110-V, 1-phase, 4-pole, 60-Hz induction motor has the following circuit constants: R1 = R2’ = 1.6 ohm,X1 = X2’ = 1.8 ohm, Xm = 60 ohm; core loss is 16 W and friction and windage loss is 12 W. Determine theefficiency of the motor at 0.04 slip by using (a) the exact equivalent circuit and (b) the approximateequivalent circuit
A three –phase, 440V, 50 Hz, 6 – pole induction motor running at 950 rpm takes 50 kW at certain load. The friction and windage loss is 1.5 kW and the stator losses = 1.2 kW. Determine the output from the rotor. (a). 42.68 kW (b). 46.48 kW (c). 48.80 kW (d). 44. 86 kW
A wound rotor, induction motor has a rotor resistance of 0.6 ohms per phase and a rotor leakage reactance of 8 ohms.a)What is the operating speed (rpm) of this 2-pole induction motor fed from a 50Hz supply if the slip is 5%?b)If maximum torque occurs when R2 = sX2, what is the slip at maximum torque?c)What resistance must be added to the rotor circuit to give maximum startingtorque?
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.
A 3 – phase induction motor has a 4 – pole, star – connected stator winding. The motorruns on a 50 – Hz supply with 200 V between lines. The rotor resistance and standstillreactance power phase are 0.1 and 0.9 ohm respectively. The ratio of rotor to stator turnsis 0.67. Calculate (a) total torque at 4 % slip, (b) total mechanical power at 4 % slip, (c)maximum torque, (d) speed at maximum torque, (e) maximum m power
im curious about #5 but its based on #4!
Please all subpart is compulsory please all subpart for like this
6- In a stepper motor, how is the speed of rotation determined? a) By the current supplied to the motor. b) By the magnitude of the voltage applied. c) By the load applied to the motor. d) By the frequency of the waveforms used. 7- A transformer core is laminated to a) reduce hysteresis loss b) reduce eddy current losses c) reduce copper losses d) reduce all above losses 8- An induction motor with 580 r.p.m. speed at 60 Hz will have a) 8 poles b) 6 poles c) 4 poles d) 2 poles 9- If any two phases for an induction motor are interchanged a) the motor will run in reverse direction b) the motor will run at reduced speed c) the motor will not run d) the motor will burn 10- No-Load speed of which of the following motor will be highest? a) Shunt motor b) Series motor c) Short-Shunt compound motor d) Long-Shunt compound motor
will give like!!
200 +21. If maximum torque of an induction motor is kg-m at a slip of 12%, the torque at 6% slip would be...... kg-m. 1 (a) 100 (b) 160 (c) 50 (d) 40 B, 1993)
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…

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