Motor speed relationship the synchronous speed of an ac motor is the speed of the rotating magnetic field set up by the stator winding synchronous speed rpm 120 x frequency divided by the number of poles. The ac motor commonly consists of two basic parts, an outside stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft producing a second rotating magnetic field. Lecture notes electrical machine ii bee 1401 page 1. Question 1 electromechanical watthour meters use an aluminum disk that is spun by an electric motor. Ac waveform and ac circuit theory ac sinusoidal waveforms are created by rotating a coil within a magnetic field and alternating voltages and currents form the basis of ac theory direct current or d. Electric motors and drives is intended for non specialist users of electric motors and drives, filling the gap between maths and theory based academic textbooks and the more prosaic handbooks, which provide useful detail but little opportunity for the development of real insight and understanding. An induction motor can therefore be made without electrical connections to the rotor.
We need not to rely on the conventional motors for all our work, and depending upon the type of work we want our machine to perform, we can select an ac or dc motor accordingly. An introduction to electric motors stmicroelectronics. Jan 06, 2019 induction motors in practice what controls the speed of an ac motor. An induction motor can be treated as a rotating transformer i. Other motors that are included are 1phase induction motors, permanent synchronous motors and synchronous reluctance motors.
A servo motor is one of the widely used variable speed drives in industrial production and process automation and building technology worldwide. The computeraided design cad files and all associated content posted to this website are created, uploaded, managed and owned by third party users. Ac motors ac motors are used worldwide in many applications to transform electrical energy into mechanical energy. These currents produce an ac flux f r which act at right angle to the stator flux f s. Ac motors principle of operation resources for engineers. Through the articles listed in this section, we will find detailed information about the working theory and operation of different types of ac and dc motors. Basic ac theory i i direct current dc alternating current ac i i figure 1. It is logical that the least expensive, lowest maintenance type motor should be used most often. If a seried dc motor has a laminated stator frame, it can run effectively htt l d iki di iki di 667 from an ac supply as well as dc, this is the.
Three phase ac motor theory motors have been described as a transformer with a rotating secondary. I then lead on to the physics behind induction motors if you find it useful, please share and subscribe for this doing the hsc. The electric energy generated purchased by consumers for different needs. An ac motor of this type may be part of a pump or fan or. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation.
The above diagram shows the configuration of stator winding. There are many types of ac motors, but this course focuses on threephase induction motors, the most common type of motor used in industrial applications. Electric motors and drives is intended for non specialist users of electric motors and drives, filling the gap between maths and theory based academic textbooks and the more prosaic handbooks, which provide useful detail but little opportunity for the. Describe how a squirrel cage motor is built, and classify it as either an induction motor or a synchronous motor. To generate a constant drag on the disk necessary to limit its rotational speed, a strong magnet is placed in such a way that its lines of magnetic flux pass perpendicularly through the.
Module 8 ac reactive components this module describes inductance and capacitance and their effects on ac circuits. The figure above shows the family tree of the ac motors described in this chapter. The three phase induction motors are simple in construction, rugged, low cost and easy to. Like most motors, an ac induction motor has a fixed outer portion, called the stator and a rotor that spins inside with a carefully engineered air gap between the two. What is common to all the members of this family is that the basic physical process involved in their operation is the conversion of electromagnetic energy to mechanical energy, and vice versa. The rotor and stator windings are connected in parallel. Virtually all electrical motors use magnetic field rotation to spin their rotors. Alternating current motors or ac motors are built on the principle that nikola tesla discovered in the late 19th century. The ac induction motor is the most used electrical motor in industrial applications worldwide. Introduction to ac motors ac motors electronics textbook. Electric motors and controls training electric motors and controls training certificate course software. Dc motors although ac motors are used in most of the cases, dc motors have many applications and used for multipurpose applications. Its operation is based on the principle that when a current carrying conductor is placed in a.
Mar 15, 2017 theory of ac series motor smile and learn. This electric motor control circuit training software is quite detailed. In contrast, when applying soft starters the motor s performance at all levels of slip is important. Ac series motor principle, types, characteristics and. Principle of ac servo motor 3 design of motor 2 stator stator is composed of the core and winding which generates torque. Induction motors in practice what controls the speed of an ac motor. The concept of the rotating magnetic field is central to ac motor theory, so it is imperative that students grasp this concept before moving on to more advanced concepts.
Therefore such motors are known as induction motors. A threephase ac induction motor is the only type where the rotating magnetic field is. Current % when applying ac speed drives the motor s low slip performance characteristics are important. Nov 20, 2016 the working principle of ac motors is given here. And, the stepper motor, a digital version of the motor, is driven by alternating current square waves, again, generated by solidstate circuitry. In the example, motor a produces twice as much torque during start as motor i. The premise for motor operation is that if you can create a rotating magnetic field in the stator of the motor, it. Singlephase induction motor threephase induction motor singlephase induction motor there are probably more singlephase ac induction motors in use today than the total of all the other types put together. Ac alternating current motors are lowcost and highefficiency mechanisms used in large variety of applications. The theory used in the work was collected by studying literature on how. Although servo motors are not a specific class of motor, they are intended and designed to use in motion control applications which require high accuracy positioning, quick reversing and exceptional. Ac series motors are also known as the modified dc series motor as their construction is very similar to that of the dc series motor.
Motor start theory motor start torque performance is indicated by the motors locked rotor torque lrt figure. There are two major components of an ac induction motor. Inverter school text inverter beginner course inverter school text inverter beginner course model model code specifications subject to change without notice. The most popular type is the 3phase, squirrelcage ac induction motor. As soon as the rotor begins to turn, a speed emf e is induced in. Other members of the family are the directcurrent dc motor or generator, the induction motor or generator, and a number of derivatives of all these three. There are many types of ac motors, but this course focuses on threephase ac induction motors, the most common type of motor used in industrial applications. Types of electric motors electric motors dc motors other motors h ac motors s unt motor separately excited induction motor stepper motor motor brushlessdc motor series motor hysteresis motor permanent magnet dc pmdc synchronous motor reluctance motor compounded motor universal motor. In the case of three phase ac alternating current operation, the most widely used motor is a 3 phase induction motor, as this type of motor does not require an additional starting device. Before we discuss these modifications, here it is essential to discuss what is the need and where do we need to do modifications.
An induction motor or asynchronous motor is an ac electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. The principle of an ac motor is that electric current is applied to electromagnets, creating a rotating magnetic field to convert electrical energy to rotation mechanical energy. Objective identify the components of an ac motor and explain their function. An induction motors rotor can be either wound type or squirrelcage. To explain the details of why this is so, a bit of background knowledge about ac. Ac induction motors how ac motors work explain that stuff. The theory used in the work was collected by studying literature on how electrical motors work, and by simplifying the. Mechanical energy what is an electric motor an electric motor is a device converting electrical energy into mechanical energy usually a torque. The two most widely used types of ac motors are induction motors and synchronous motors.
An electrical motor is an electromechanical device which converts electrical energy into mechanical energy. Crosssection of a onephase permanent magnet ac motor with flux lines plot. Ac drive theory and application application guide ap04014005e effective. An ac motor is an electric motor driven by an alternating current ac.
Volume 3 of 4 module 7 basic ac theory this module describes the basic concepts of alternating current ac electrical circuits and discusses the associated terminology. Module 6 dc motors this module describes the types of dc motors and includes discussions of speed control, applications, and load characteristics. Single phase induction motor, theory of operation double revolving field theory, equivalent circuit, determination of. The field windings of a series motors are connected in series with the armature windings. Motor start theory low slip v full slip 0 50 100 150 200 250 300. Nov 27, 2019 an electrical motor is an electromechanical device which converts electrical energy into mechanical energy. These types of motors are known as selfstarting induction motors. Ac motors are electric motors driven by alternating current ac. Basically, an ac motor is a type of motor that is operated by an alternating current. If you happen to have a string of blinking christmas lights to use as a prop in illustrating a rotating magnetic field, this would be a good thing to show your students. Applications of threephase induction motors of size varying. Pdf torque behavior of onephase permanentmagnet ac motor. In this video i discuss ac motors, in particular, synchronous motors. The most common type of ac motor being used throughout the work today is the induction motor.
Ac motors offer a simple design, consisting of a magnetically driven, copper wounded stator and a rotor mechanism. An engineering guide to ac and dc motor designs and operation. This exam will test you level of comprehension on the basic ac theory section of the electrical training course. In fact, ac and dc motor designs are very similar to their generator counterparts identical for the sake of this tutorial, the ac motor being dependent upon the reversing magnetic. A universal motor is a singlephase series motor, which is able to run on either alternating current ac or direct current dc and the characteristics are similar for both ac and dc. Overview the acdc motor theory course was specifically developed for electricians and electronic technicians as well as for the multicraft training needs of process and manufacturing facilities.
Ac motors are used worldwide in many applications to transform electrical energy into mechanical energy. Explain how this motor can be operated as either a synchronous motor or a plain induction motor. Free ac motors books download ebooks online downloadable ebooks downloads zip chm rar. Solenoids, timers, sensors, relays, troubleshooting, even an introduction to. Direct vs alternating current distribution systemsthat are far more ef. An887, ac induction motor fundamentals microchip technology. It is virtually impossible for the rotor of an ac induction motor to turn at the same speed as the rotating magnetic field. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. Ac induction motor speed control so what can we do to control the speed of an ac induction motor. Dc motor principle a machine that converts dc power into mechanical energy is known as dc motor. The rotor magnetic field may be produced by permanent.
The split facing technique of ac motors is given in this video. Module 7 basic ac theory this module describes the basic concepts of alternating current ac electrical circuits and discusses the associated terminology. Basic design and theory of operation the alternating current ac induction motor is one of the most rugged and most widely used machines in industry. The theoretical speed of the rotor in an induction motor depends on the frequency of. Motors, generators, and transformers are similar in that their basic principle of operation involves induction. The sinamics dc master cabinets can be directly connected to threephase systems up to 3 ac950 v, and in the basic version they cover a power range between 6 and 2500 kw. In ac motors, the input alternating current creates a rotating magnetic field over the. Doehdbk10192 june 1992 doe fundamentals handbook electrical science volume 3 of 4 u. Also ac series motor is a modified dc series motor what does this mean. Ac motors are widely used in industry, primarily due to their high efficiency, and their ability to produce constant torque up to the rated speed. May 2008 induction motor speed control standard induction motors nema design b have approximately 3% slip at full load. If the drive only controls the output frequency, the motor speed will deviate from the set speed due to slip. Ac series motor or the universal motor is an electric motor which operates in either ac or dc power at the same speed and output.
265 1453 1014 1302 1413 438 317 511 714 833 519 1079 299 331 1264 88 244 733 12 1520 398 1254 1356 881 1470 1044 1038 6 1402 724 1199 857 738 1404 393 790 1429 418 371 132