Basics Of AC Motors-Chapter 1rev
Basics of AC MotorsA quickSTEP Online Course Siemens Industry, Inc.www.usa.siemens.com/step
TrademarksSiemens is a trademark of Siemens AG. Product names mentioned may be trademarks or registeredtrademarks of their respective companies.National Electrical Code and NEC are registered trademarks of the National Fire ProtectionAssociation, Quincy, MA 02169.NEMA is a registered trademark and service mark of the National Electrical Manufacturer’sAssociation, Rosslyn, VA 22209.Underwriters Laboratories Inc. and UL are registered trademarks of Underwriters Laboratories, Inc.,Northbrook, IL 60062-2026.Other trademarks are the property of their respective owners. Siemens Industry, Inc. 2016Page 1-2
Course TopicsWelcome to Basics of AC Motors. This coursecovers the following topics:Chapter 1 - Introduction Basic ConceptsChapter 2 – Motor Basics Electromagnetism Rotor RotationChapter 3 – NEMA Motors Motor Designs Motor EnclosuresChapter 4 – Siemens Motors NEMA Motors IEC Motors Above NEMA MotorsIf you do not have an understanding of basicelectrical concepts, you should complete Basicsof Electricity before attempting this course. Siemens Industry, Inc. 2016Page 1-3
Course ObjectivesUpon completion of this course you will be able to Explain the concepts of force, inertia, speed, and torque Explain the difference between work and power Describe the construction of a squirrel cage AC motor Describe the operation of a rotating magnetic field Calculate synchronous speed, slip, and rotor speed Identify the starting torque, pull-up torque, breakdown torque, and full-load torque on aNEMA B motor speed-torque curve Describe the information displayed on a NEMA motor nameplate Identify important motor derating factors Identify NEMA enclosures and mounting configurations Summarize the types of Siemens SIMOTICS motors available Siemens Industry, Inc. 2016Page 1-4
SIMOTICS MotorsThis course primarily focuses on building your basic knowledge of NEMA three-phase induction motors, which are part ofSiemens extensive SIMOTICS motor product line. SIMOTICS industrial electric motors provide you with the optimumsolution for every application. Backed by 150 years of experience, SIMOTICS motors are unrivaled when it comes toreliability, ruggedness, compactness, efficiency, and performance. SIMOTICS electric motors include: Low voltage AC motors for line and converter operation Precise motion control motors with highly-dynamic performance for positioning and handling, as well as for use inproduction machines and machine tools DC motors and powerful high-voltage motors for use in ships, rolling mills, ore mills, and large mud pumps andcompressors in the oil and gas industry Siemens Industry, Inc. 2016Page 1-5
SITRAIN Training for IndustryOnline Self-paced Learning – Programs with maximum flexibility so students can easily fitcourses into their busy schedulesVirtual Instructor-led Learning - Classroom lectures delivered in the convenience of yourhome or officeClassroom Learning - Expert and professional instructors, proven courseware, and qualityworkstations combine for the most effective classroom experience possible at your facility oroursHow-to Video Library - Quick, affordable, task-based learning options for a broad range ofautomation topics for training or purchaseSimulators - World-class simulation systems available for training or purchaseThis course also describes learning options available from the Siemens SITRAIN USA organization and ourglobal SITRAIN partners. For additional information: www.usa.siemens.com/sitrain Siemens Industry, Inc. 2016Page 1-6
Chapter 1 – IntroductionThis chapter covers the followingtopic: Basic Concepts AC Motor Construction Siemens Industry, Inc. 2016Page 1-7
AC MotorsAC motors are used worldwide in many applications totransform electrical energy into mechanical energy. Thereare many types of AC motors, but this course focuses onthree-phase induction motors, the most common type ofmotor used in industrial applications.An AC motor of this type may be part of a pump or fan orconnected to some other form of mechanical equipmentsuch as a winder, conveyor, or mixer. Siemensmanufactures a wide variety of AC motors.In addition to providing basic information about AC motorsin general, this course also includes an overview ofSiemens SIMOTICS NEMA AC motors, which range fromgeneral purpose motors in Aluminum frame, tosophisticated three-phase motors that meet or exceedIEEE 841 and NEMA Premium standards.Some summary information is also included for SiemensIEC and Above NEMA motors. Siemens Industry, Inc. 2016Page 1-8
Standards OrganizationsThroughout this course, reference is made to the NationalElectrical Manufacturers Association (NEMA). NEMAdevelops standards for a wide range of electrical products,including AC motors. For example, NEMA StandardPublication MG 1 covers NEMA frame size AC motors,commonly referred to as NEMA motors.In addition to manufacturing NEMA motors, Siemens alsomanufactures motors larger than the largest NEMA framesize. These motors are built to meet specific applicationrequirements and are commonly referred to as aboveNEMA motors.Siemens also manufactures motors to InternationalElectrotechnical Commission (IEC) standards. IEC isanother organization responsible for electrical standards.IEC standards perform the same function as NEMAstandards, but differ in many respects. In many countries,electrical equipment is commonly designed to comply withIEC standards. In the United States, although IEC motorsare used, NEMA motors are more common. Keep in mind,however, that many U.S.-based companies build productsfor export to countries that follow IEC standards. Siemens Industry, Inc. 2016Page 1-9
ForceBefore discussing AC motors and drives, it is necessary todiscuss some of the basic terminology associated with theiroperation.In simple terms, a force is a push or pull. Force may becaused by electromagnetism, gravity, or a combination ofphysical means.Net force is the vector sum of all forces that act on anobject, including friction and gravity. When forces areapplied in the same direction, they are added.For example, if two 10 pound forces are applied in thesame direction, the net force is 20 pounds. If 10 pounds offorce is applied in one direction and 5 pounds of force isapplied in the opposite direction, the net force is 5 pounds,and the object moves in the direction of the greater force. If10 pounds of force is applied equally in both directions, thenet force is zero, and the object does not move. Siemens Industry, Inc. 2016Page 1-10
TorqueTorque is a twisting or turning force that causes an object torotate. For example, a force applied to a point on a leverapplies a torque at the pivot point.Torque is the product of force and radius (lever distance).Torque Force x RadiusIn the English system of measurements, torque ismeasured in pound-feet (lb-ft) or pound-inches (lb-in). Forexample, if 10 lbs of force is applied to a lever 1 foot long,the resulting torque is 10 lb-ft.An increase in force or radius results in a correspondingincrease in torque. Increasing the radius to two feet, forexample, results in 20 lb-ft of torque. Siemens Industry, Inc. 2016Page 1-11
SpeedAn object in motion takes time to travel any distance. Speedis the ratio of the distance traveled and the time it takes totravel the distance.Linear speed is the rate at which an object travels aspecified distance in one direction. Linear speed isexpressed in units of distance divided by units of time.This results in compound speed units such as miles perhour or meters per second (m/s). Therefore, if it takes 2seconds to travel 10 meters, the speed is 5 m/s. Siemens Industry, Inc. 2016Page 1-12
Angular SpeedThe angular speed, also called rotational speed, of arotating object determines how long it takes for an object torotate a specified angular distance.Angular speed is often expressed in revolutions per minute(RPM). For example, an object that makes ten completerevolutions in one minute has a speed of 10 RPM. Siemens Industry, Inc. 2016Page 1-13
AccelerationAn increase in speed is called acceleration. Accelerationoccurs when there is an increase in the force acting on theobject or a reduction in its resistance to motion.A decrease in speed is called deceleration. Decelerationoccurs when there is a decrease in the force acting on andobject or an increase in its resistance to motion.For example, a rotating object can accelerate from 10 RPMto 20 RPM or decelerate from 20 RPM to 10 RPM. Siemens Industry, Inc. 2016Page 1-14
Inertia and LossesMechanical systems are subject to the law of inertia. Thelaw of inertia states that an object will remain in its currentstate of rest or motion unless acted upon by an externalforce. This property of resistance to acceleration anddeceleration is referred to as the moment of inertia. TheEnglish system unit of measurement for inertia is poundfeet squared.For example, consider a machine that unwinds a large rollof paper. If the roll is not moving, it takes a force toovercome inertia and start the roll in motion. Once moving,it takes a force in the reverse direction to bring the roll to astop.Any system in motion has losses that drain energy from thesystem. The law of inertia is still valid, however, becausethe system will remain in motion at constant speed if energyis added to the system to compensate for the losses.Friction is one of the most significant causes of energy lossin a machine. Friction occurs when objects contact oneanother. For example, to move one object across thesurface of another object, you must apply enough force toovercome friction. Siemens Industry, Inc. 2016Page 1-15
Work and PowerWhenever a force causes motion, work is accomplished.Work is calculated by multiplying the force that causes themotion times the distance the force is applied.Because work is the product of force times the distanceapplied, work can be expressed in any compound unit offorce times distance. For example, work is commonlyexpressed in joules. 1 joule is equal to 1 newton-meter, aforce of 1 newton for a distance of 1 meter. In the Englishsystem of measurements, work is often expressed in footpounds (ft-lb), where 1 ft-lb equals 1 foot times 1 pound.Another often used quantity is power. Power is the rate ofdoing work, which is the amount of work done in a period oftime. Siemens Industry, Inc. 2016Page 1-16
Horsepower and KilowattsPower can be expressed in foot-pounds per second, but isoften expressed in horsepower. This unit was defined in the18th century by James Watt. Watt sold steam engines andwas asked how many horses one steam engine wouldreplace. He had horses walk around a wheel that would lifta weight. He found that a horse would average about550 foot-pounds of work per second. Therefore, onehorsepower is equal to 550 foot-pounds per second or33,000 foot-pounds per minute.When applying the concept of horsepower to motors, it isuseful to determine the amount of horsepower for a givenamount of torque and speed. When torque is expressed inlb-ft and speed is expressed in RPM the formula forhorsepower (HP) shown in the accompanying graphic canbe used. Note that a change in torque or speed alsochanges horsepower.AC motors manufactured in the United States are generallyrated in horsepower, but motors manufactured in manyother countries are rated in kilowatts (kW). Fortunately it iseasy to convert between these units as shown in theaccompanying graphic. Siemens Industry, Inc. 2016Page 1-17
Chapter 1 – IntroductionThis chapter covers the followingtopic: Basic Concepts AC Motor Construction Siemens Industry, Inc. 2016Page 1-18
AC Motor ConstructionThree-phase induction motors are commonly used inindustrial applications. This type of motor has the followingthree main parts: rotor, stator, and enclosure. The statorand rotor do the work, and the enclosure protects the statorand rotor. Siemens Industry, Inc. 2016Page 1-19
Stator CoreThe stator is the stationary part of the motor’selectromagnetic circuit. The stator core is made up of manythin metal sheets, called laminations. Laminations are usedto reduce energy loses that would result if a solid core wereused. Siemens Industry, Inc. 2016Page 1-20
Stator WindingsStator laminations are stacked together forming a hollowcylinder. Coils of insulated wire are inserted into slots of thestator core.When the assembled motor is in operation, the statorwindings are connected directly to the power source. Eachgrouping of coils, together with the steel core it surrounds,becomes an electromagnet when current is applied.Electromagnetism is the basic principle behind motoroperation. Siemens Industry, Inc. 2016Page 1-21
Rotor Construction – Part 1The rotor is the rotating part of the motor’s electromagneticcircuit. The most common type of rotor used in a threephase induction motor is a squirrel cage rotor.The squirrel cage rotor is so called because its constructionis reminiscent of the rotating exercise wheels found in somepet cages. A squirrel cage rotor core is made by stackingthin steel laminations to form a cylinder. Siemens Industry, Inc. 2016Page 1-22
Rotor Construction – Part 2Rather than using coils of wire as conductors, conductorbars are die cast into the slots evenly spaced around thecylinder. Most squirrel cage rotors are made by die castingaluminum to form the conductor bars. Siemens also makesmotors with die cast copper rotor conductors.After die casting, rotor conductor bars are mechanically andelectrically connected with end rings. The rotor is thenpressed onto a steel shaft to form a rotor assembly. Siemens Industry, Inc. 2016Page 1-23
EnclosureThe enclosure consists of a frame (or yoke) and two endbrackets (or bearing housings). The stator is mountedinside the frame. The rotor fits inside the stator with a slightair gap separating it from the stator. There is no directphysical connection between the rotor and the stator.The enclosure protects the internal parts of the motor fromwater and other environmental elements. The degree ofprotection depends upon the type of enclosure. Enclosuretypes are discussed later in this course. Siemens Industry, Inc. 2016Page 1-24
Bearings and FanBearings, mounted on the shaft, support the rotor and allowit to turn. Some motors, like the one shown in theaccompanying illustration, use a fan, also mounted on therotor shaft, to cool the motor when the shaft is rotating. Siemens Industry, Inc. 2016Page 1-25
Online Self-paced LearningWith Siemens online self-paced learning, you select thetopics and set you own pace for completing chosencourses. Because all course material is online, you canstart learning as soon as you purchase a subscription.You can choose from over 500 courses consisting of highquality graphics, on-screen text, supporting voiceovernarration, and interactive exercises. Features includeprintable course content for reference and underlined keyvocabulary terms with definitions displayed with a simplemouse-over action.Depending on the subscription purchased, you can chooseany 10 or 25 courses or select the entire online self-pacedcourse catalog.These courses are offered 24/7/365, so you can begin yoursubscription at any time. From the date of registration,you are given one year to complete their course selections.For additional information: www.usa.siemens.com/sitrain Siemens Industry, Inc. 2016Page 1-26
Chapter 2 – Motor BasicsThis chapter covers the followingtopics: Electromagnetism Rotor Rotation Siemens Industry, Inc. 2016Page 2-1
MagnetismThe principles of magnetism play an important role in theoperation of an AC motor. Therefore, in order to understandmotors, you must understand magnets.To begin with, all magnets have two characteristics. Theyattract iron and steel objects, and they interact with othermagnets. This later fact is illustrated by the way a compassneedle aligns itself with the Earth’s magnetic field. Siemens Industry, Inc. 2016Page 2-2
Magnetic Lines of FluxThe force that attracts an iron or steel object hascontinuous magnetic field lines, called lines of flux, that runthrough the magnet, exit the north pole, and return throughthe south pole.Although these lines of flux are invisible, the effects ofmagnetic fields can be made visible. For example, when asheet of paper is placed on a magnet and iron filings areloosely scattered over the paper, the filings arrangethemselves along the invisible lines of flux. Siemens Industry, Inc. 2016Page 2-3
Magnetic PolesThe polarities of magnetic fields affect the interactionbetween magnets. For example, when the opposite poles oftwo magnets are brought within range of each other, thelines of flux combine and pull the magnets together.However, when like poles of two magnets are broughtwithin range of each other, their lines of flux push themagnets apart. In summary, unlike poles attract and likepoles repel. The attracting and repelling action of themagnetic fields is essential to the operation of AC motors. Siemens Industry, Inc. 2016Page 2-4
ElectromagnetismWhen current flows through a conductor, it produces amagnetic field around the conductor. The strength of themagnetic field is proportional to the amount of current. Siemens Industry, Inc. 2016Page 2-5
Left Hand Rule for ConductorsThe left hand rule for conductors demonstrates therelationship between the flow of electrons and the directionof the magnetic field created by this current. If a currentcarrying conductor is grasped with the left hand with thethumb pointing in the direction of electron flow, the fingerspoint in the direction of the magnetic lines of flux.The accompanying illustration shows that, when theelectron flow is away from the viewer (as indicated by theplus sign), the lines of flux flow in a counterclockwisedirection around the conductor. When the electron flowreverses and current flow is towards the viewer (asindicated by the dot), the lines of flux flow in a clockwisedirection. Siemens Industry, Inc. 2016Page 2-6
ElectromagnetAn electromagnet can be made by winding a conductor intoa coil and applying a DC voltage. Because the coilconcentrates the lines of flux formed by current flow throughthe conductor, the magnetic field in or near the coil isstrengthened. The center of the coil is known as the core.This simple electromagnet has an air core. Siemens Industry, Inc. 2016Page 2-7
Magnetic Field StrengthIron conducts magnetic flux more easily than air. When aninsulated conductor is wound around an iron core, astronger magnetic field is produced for the same level ofcurrent.The strength of the magnetic field created by theelectromagnet can be increased further by increasing thenumber of turns in the coil. The greater the number of turns,the stronger the magnetic field for the same level of current. Siemens Industry, Inc. 2016Page 2-8
Applying an AC SourceThe magnetic field of an electromagnet has the samecharacteristics as a natural magnet, including a north andsouth pole. However, when the direction of current flowthrough the electromagnet changes, the polarity of theelectromagnet changes. As shown in the accompanyinggraphic, the polarity of an electromagnet connected to anAC source changes at the frequency of the AC source.At time 1, there is no current flow, and no magnetic field isproduced. At time 2, current is flowing and a magnetic fieldbuilds up around the electromagnet. Note that the southpole is on the top and the north pole is on the bottom. Attime 3, current flow is at its peak, and the strength of themagnetic field has also peaked. At time 4, current flowdecreases, and the magnetic field begins to collapse.At time 5, no current is flowing and no magnetic field isproduced. At time 6, current is increasing in the oppositedirection. Note that the polarity of the elec
AC Motors AC motors are used worldwide in many applications to transform electrical energy into mechanical energy. There are many types of AC motors, but this course focuses on three-phase induction motors, the most common type of motor used in industrial applications. An AC motor of this type may be part of a pump or fan or
Part One: Heir of Ash Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26 Chapter 27 Chapter 28 Chapter 29 Chapter 30 .
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Motors with corrosion resistant parts Wheel motors with recessed mounting flange OMP, OMR- motors with needle bearing OMR motor in low leakage version OMR motors in a super low leakage version Short motors without bearings Ultra short motors Motors with integrated positive holding brake Motors with integrated negative holding brake .
DEDICATION PART ONE Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 PART TWO Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 .
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the supplier's works. Squirrel-cage and slip-ring motors in mechanical/electrical modifications: Three-phase motors for use aboard ships, squirrel-cage type 0.09 - 490 kW Three-phase motors to IEC/DIN, squirrel-cage type 0.06 - 500 kW Three-phase motors, squirrel-cage type 2.2 - 315 kW Three-phase brake motors 0.12 .
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