Electrical Transformers and Rotating Machines
4th Edition
ISBN: 9781305494817
Author: Stephen L. Herman
Publisher: Cengage Learning
expand_more
expand_more
format_list_bulleted
Concept explainers
Textbook Question
Chapter 17, Problem 22RQ
A three-phase squirrel-cage motor is connected to a 60-Hz line. The full-load speed is 870 RPM. How many poles per phase does the stator have?
Expert Solution & Answer
Want to see the full answer?
Check out a sample textbook solutionStudents have asked these similar questions
A 7460 W split-phase motor running at 1750 rpm is used to drive a rotary pump. The pump should run continuously at approximately 1175 rpm. The center distance should not exceed 1118 mm. Space limits the diameter of the driven pulley to 292 mm.
Determine:
a. the pulley diameters,
b. the belt size, and
c. the number of belt required.
QUESTION 8
Consider the equations of motion of an armature controlled DC motor given by
Jw(t)+bw (t) Ki(t) = -Tfriction - Tload (t)
di (t)
+ Ri (t) + Kw (t) =
Vin (t),
dt
where vin(t) is the input voltage and Tload(t) is the input load torque. The outputs are the armature current i(t) and the motor speed w(t).
The steady-state response of motors are specified by nominal voltage, stall torque, stall current, no load speed, and no load current.
At steady-state operation, the motor equations satisfy
bo) -Ki =-T -T.
fric
load
Ri +Kov_-
55
55
The stall torque is the load torque required stead-state speed of the motor is zero.
The stall current is the armature current when the motor speed is zero.
The no load speed is the speed of motor when the load torque is zero.
The no load current is the current when the load torque is zero.
What is stall torque for this motor in N-m? Keep 3 significant figures, and do not include units. Use Scientific notation.
The constants are given below.
Nominal…
In speed coontrol of dc motor, the final control element is motor.
Select one:
O True
False
Chapter 17 Solutions
Electrical Transformers and Rotating Machines
Ch. 17 - Prob. 1RQCh. 17 - Prob. 2RQCh. 17 - What is synchronous speed?Ch. 17 - What two factors determine synchronous speed?Ch. 17 - Name three factors that cause the magnetic field...Ch. 17 - Name three factors that determine the torque...Ch. 17 - Is the synchronous motor an induction motor?Ch. 17 - What is the amortisseur winding?Ch. 17 - Prob. 9RQCh. 17 - Prob. 10RQ
Ch. 17 - Prob. 11RQCh. 17 - Why can an induction motor never operate at...Ch. 17 - Prob. 13RQCh. 17 - Prob. 14RQCh. 17 - Prob. 15RQCh. 17 - Prob. 16RQCh. 17 - Prob. 17RQCh. 17 - Prob. 18RQCh. 17 - Prob. 19RQCh. 17 - Prob. 20RQCh. 17 - How is the speed of a consequent pole...Ch. 17 - A three-phase squirrel-cage motor is connected to...
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.Similar questions
- As shown in the figure below, this is a speed regulation method for DC separately excited motor. a) What is the speed regulation method? b) What are the characteristics for this speed regulation method? B no Ra le lo R: '3 E R3 Tr. Tarrow_forwardin a dc machine 72 number of coils are used. Find the number of commutator ?segments required 74 72 37 36arrow_forwardThe supply frequency is 50 Hz. What will be the rotor voltage frequency if the motor speed is equal to 90% of synchronous speed. O 45 Hz. O 10 Hz. 05 Hz. O None.arrow_forward
- Problem 1 3-Phase AC Machinery Principles Part 1: Complete the following table by calculating the speed of magnetic field rotation in AC machines depending on the number of poles and the operating frequency. Number of Speed (RPM) Poles Frequency f = 50 Hz Frequency f= 60 Hz 4 6. 10 Solutionarrow_forwardA 50 Hz pump drive requires a torque of 70 Nm approx. at 1450 rpm approx. for 1 minute followed by 5 minutes running unloaded. This cyclic pattern is repeated continuously. The motor is to be selected from a range of general-purpose motors with continuous ratings of 2.2, 3, 4, 5.5, 7.5, 11, 15 and 20 kW. The motors have a pull-out torque of 200%. 1. Select the pole number. 2. Calculate the continuous power rating. 3. 4. Calculate the required power rating given the pull out torque rating. Estimate the slip when the motor drives the pump at the required speed. Choose the motor from the range of options that is most fit for purpose. 5. Enter your answers in the units indicated (without unit symbols) corrected if necessary to two decimal places. Answer: Number of poles= ✓ Continuous power rating (kW)= Required power rating for 200% pull out torque (kW)= Percentage slip (%) = Most suitable motor from given range (kW)-arrow_forwardCalculate the percentage speed regulation of a motor at full load if the machine runs at 1000 rpm at no-load and the full load speed is 900 rpm.arrow_forward
- A 480V, 3-phase, 50Hz 6-pole Induction motor with a rated power of 10KVA. (i) Calculate the synchronous speed in rad/sec (ws) (ii) Determine the rotor speed in rpm, if the % slip is 2.5%arrow_forwardQuestion 2 Beli vifth Slack side Motor (imprut) Tight side Beli thickpess\ Centre distance Figure 2 Figure 2 shows an open flat belt drive connected to a motor and a pulley. The motor transmits 20 kw to the connect pulley of 450 mm diameter and is rotating at 850 r/min to a second pulley rotating at 400 r/min. The distance between pulley centres is approximately 2 m. The belt is 6 mm thick and has a density of 970 kg/m. The maximum stress in the belt is not to exceed 2,7 MPa. The coefficient of friction for both pulleys is 0,3. Determine: 2.1. The diameter of the second pulley. 2.2. The length of the belt. 3.3. The width of the belt taking centrifugal tension into account.arrow_forwardQUESTION 1 Consider the equations of motion of an armature controlled DC motor given by Jw(t)+bw (t) Ki (t) = di (l) L + Ri (t) + Kw (t) = -Tfriction - Tload (t) Vin (t), dt where vin(t) is the input voltage and Tload(t) is the input load torque. The outputs are the armature current i(t) and the motor speed w(t). When the input voltage and torque are constant, the transient response of this system has the form of the homogeneous solution. What is the time constant of the transient response? Find the characteristic roots of this system first. Keep 3 significant figures, and do not include units. Use scientific notation. The constants are given below: Nominal voltage, Vin(t) = 17 V Moment of inertia of the rotor, J = 0.02 kg-m² Motor viscous friction constant, b = 0.009 N-m-s Friction torque, Tfric = 0.003 N-m Armature inductance, L = 0.1 H Armature resistance, R = 0.35 Back emf constant and motor torque constant, K = 0.21 N-m/A. **Recall that the time constant (or relaxation time) is…arrow_forward
- An industrial fan running at 600 rpm is driven by a 25-kW, 960 rpm, induction motor. The pulley mounted on the motor shaft is 270 mm. Center to center distance is 1.5 meters and use f = 0.35. Determine the minimum angle of wrap in rad.arrow_forwardAn AC power source is connected across 325 turns of an autotransformer, and the load is connected across 260 turns. What is the turns ratio of this transformer?arrow_forwarda 7460 w split-phase motor running at 1750 rpm is used to drive a rotary pump. the pump should run continuously at approximately 1175 rpm. the center distance should not exceed 1118 mm. space limits the diameter of the driven pulley to 292 mm. design a. the pulley diameters, b. the belt size, and c. the number of belt required.arrow_forward
arrow_back_ios
arrow_forward_ios
Recommended textbooks for you
- Electrical Transformers and Rotating MachinesMechanical EngineeringISBN:9781305494817Author:Stephen L. HermanPublisher:Cengage LearningUnderstanding Motor ControlsMechanical EngineeringISBN:9781337798686Author:Stephen L. HermanPublisher:Delmar Cengage Learning
Electrical Transformers and Rotating Machines
Mechanical Engineering
ISBN:9781305494817
Author:Stephen L. Herman
Publisher:Cengage Learning
Understanding Motor Controls
Mechanical Engineering
ISBN:9781337798686
Author:Stephen L. Herman
Publisher:Delmar Cengage Learning
Fluid Mechanics - Viscosity and Shear Strain Rate in 9 Minutes!; Author: Less Boring Lectures;https://www.youtube.com/watch?v=_0aaRDAdPTY;License: Standard youtube license