AC Motor
An AC motor is a type of electric motor that operates on alternating current. It consists of a stator and a rotor, with the stator producing a rotating magnetic field that drives the rotation of the rotor. AC motors are commonly used in various applications, including industrial machinery, household appliances, and electric vehicles.
8 Key excerpts on "AC Motor"
eBook - ePub- Sivaraman Palanisamy, Sharmeela Chenniappan, A. Thaiyal Nayagi, R. Mahendran(Authors)
- 2020(Publication Date)
- Wiley-Scrivener(Publisher)
...4 AC Machines 4.1 Introduction An electric motor is a device which is used to convert the electrical energy into rotating mechanical energy. This rotating mechanical energy is used for various applications like fans, drives, water pumping, etc. The motors that operate in DC power supply are called DC motors and the motors operating in AC power supply are called AC Motors [1, 17]. Based on the operation, AC Motors are classified into the following types: i) Induction motors ii) Synchronous motors iii) Special purpose motors Based on the number of phases, AC Motors are classified into the following types: i) Single-phase motors ii) Three-phase motors 4.2 Three-Phase Induction Motor Three-phase induction motors are widely used for various residential, commercial, industrial and agricultural applications [4, 6]. The advantages of three-phase induction motors over other types of motors are: i) Induction motors have a self-starting property and no need for external starting devices ii) High power factor iii) Simple and rugged construction iv) High reliability v) Efficiency is high vi) Low cost vii) Good speed regulation viii) Less maintenance is required The three-phase induction motor works on the principles of Rotating Magnetic Field (RMF). 4.2.1 Rotating Magnetic Field The RMF is defined as the magnetic field or flux having constant amplitude and its axis continuously rotating in a plane with a certain speed. When a balanced three-phase voltage is supplied to a balanced three-phase winding of an electric motor, it produces RMF at constant magnitude [2]. This RMF field is also called synchronous speed. 4.2.2 Construction Basically, the induction motor consists of two main parts, namely: i) Stator – stationary part of the motor ii) Rotor – rotating part of the motor The conversion of electrical energy into rotating mechanical energy takes place in the rotor. Hence the rotor develops a driving torque and rotates. A...
- Dave Polka(Author)
- 2020(Publication Date)
- International Society of Automation(Publisher)
...3 AC and DC Motors Introduction To truly understand the operating principles of an electronic drive, it is first necessary to understand basic AC and DC motor theory. As covered previously, the drive is the device that controls the motor. The drive and motor interact to provide the torque, speed, and horsepower necessary to operate the application. Slight differences occur between manufacturers when it comes to motor design, but the basic characteristics apply no matter which motor is being controlled. DC motors have been the backbone of industrial applications ever since the Industrial Revolution. This is because of the DC motor’s high starting torque capability, smooth speed control, and ability to quickly accelerate to speed in the opposite direction. Several newer motor types have been used in industrial applications in recent years. Permanent magnet AC Motors and synchronous reluctance motors are being used in high-speed applications where energy efficiency and high torque/small size is an advantage. The appendices provide more information on the ideas and terms presented in this chapter. You will also find helpful equations and conversions related to both DC and AC Motors. DC Motors: General Principles of Operation Basic Components Two basic circuits are in any DC motor: the armature (the device that rotates, sometimes referred to as a rotor) and the field (the stationary part, sometimes referred to as a stator). The two components magnetically interact with one another to produce rotation in the armature. We will take a closer look at each of the parts and how they interact. Figure 3-1 is a simple illustration of the basic parts of the DC motor. As shown in the figure, the armature and the field are two separate circuits and are located next to each other to promote magnetic interaction. Figure 3-1. DC motor basic parts. The armature has an integral part called a commutator...
eBook - ePub- David Wyatt, Mike Tooley(Authors)
- 2018(Publication Date)
- Routledge(Publisher)
...If a current of 8 A is supplied to each load, determine the total power supplied by the system. In a three-phase system the line voltage is 105V and the line current is 8A. If the power factor is 0.75 determine the total power supplied. 4.4 AC Motors Figure 4.32 A complete delta-connected three-phase distribution system AC Motors offer significant advantages over their DC counterparts. AC Motors can, in most cases, duplicate the operation of DC motors and they are significantly more reliable. The main reason for this is that the commutator arrangements (i.e. brushes and slip-rings) fitted to DC motors are inherently troublesome. Because the speed of an AC Motor is determined by the frequency of the AC supply that is applied to it, AC Motors are well suited to constant-speed applications. AC Motors are generally classified into two types: synchronous motors induction motors. The synchronous motor is effectively an AC generator (i.e. an alternator) operated as a motor. In this machine, AC is applied to the stator and DC is applied to the rotor. The induction motor is different in that no source of AC or DC power is connected to the rotor. Of these two types of AC Motor, the induction motor is by far the most commonly used. Key point The principle of all AC Motors is based on the generation of a rotating magnetic field. It is this rotating field that causes the motor's rotor to turn. 4.4.1 Producing a rotating magnetic field Before we go any further it's important to understand how a rotating magnetic field is produced. Take a look at Fig. 4.33 which shows a three-phase stator to which three-phase AC is applied. The windings are connected in delta configuration, as shown in Fig. 4.34. It is important to note that the two windings for each phase (diametrically opposite to one another) are wound in the same direction. At any instant the magnetic field generated by one particular phase depends on the current through that phase...
eBook - ePub- Howard W. Penrose(Author)
- 2014(Publication Date)
- Success By Design(Publisher)
...Chapter 3 Electric Motor Theory Most textbooks separate AC and DC motor theory and treat them separately. In this case, we are going to treat all types of AC and DC electric motors working from the basic theories of AC and DC machines. This understanding of operating theory is important for the analysis of an electric machine. AC Induction Motor Theory The simplified circuit for one phase of a three phase induction motor can be found in Figure 10. As you can see, the circuit consists of resistance, inductance, capacitance, inductive and capacitive reactances and the overall impedance. Figure 10: Basic Motor Circuit The AC induction motor consists of a number of basic components. Those include the following: • The stator frame: This component protects the interior of the electric motor and contains components of the electric motor. For most motors, the surface of the stator frame is set up to expel heat from the stator core. • The end shields: Coupled with the stator frame, the end shields protect the interior of the electric motor and hold the bearings centered through stator. • The bearings: Hold the rotor centered within the motor airgap while reducing the friction of the operation of the motor. • The stator core: The stator core both holds the stator windings and directs the magnetic fields developed in towards the airgap (space between stator and rotor cores). The material used is selected to reduce hysteresis losses (the resistance to a changing magnetic field) and is generally 19 to 49 mils thick and insulated from each other in order to reduce eddy-current losses. Older core steels tended to be a low-carbon annealed steel with energy and premium efficient motors requiring silicone steels. The laminations are stamped or cut (laser) in such a way that they have the same magnetic ‘grain’ as well as slots for the stator windings...
eBook - ePub- S. Bobby Rauf(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...7 Electrical Machines – Motors and Generators Introduction Electromechanical rotating machines can be generators or motors. Rotating machines are called motors when they consume electrical energy or convert electrical energy into mechanical energy, work, or torque. Rotating machines are referred to as generators when they produce electrical energy from mechanical energy, work, or torque. In practical applications, while direct current (DC) machines are almost always single-phase, alternating current (AC) machines can be single-phase or three-phase. In this chapter, we will explore fundamental operating principles and concepts associated with DC and AC Motors and generators. The electromagnetic principles behind the operation of generators and motors will be illustrated through simplified electrical diagrams. Basic principles and equations governing important and practical functions and operational parameters of motors and generators will be introduced. Common calculations involving electric motors will be illustrated. Concept of induction motor slip is explained and associated calculations are covered. DC Generator A DC generator, also referred to as a dynamo, is an electromagnetic device designed to convert mechanical energy or mechanical power – namely, brake horsepower – to electrical energy or electrical power. The electrical energy and power developed in DC dynamos consist of DC and DC voltage. A DC generator is, fundamentally, an AC generator. The feature that differentiates a DC generator’s function and output from an AC generator is called a “commutator.” Common commutator consists of two rings as shown in Figure 7.1...
- S. Bobby Rauf(Author)
- 2021(Publication Date)
- River Publishers(Publisher)
...Case in point, the application of DC motors as the motive power in locomotives. An advantage of DC motors is that they can be operated directly from DC power supply, with variable voltage, without the need for an inverter. This positions DC motors well for electric vehicles application. Albeit, the contemporary EVs, electric vehicles, are now utilizing mostly AC Motors, powered by inverter drives. Yet, despite the dominance of AC induction motors in myriad applications, DC motors continue to play an important role in providing motive power in small toys and disk drives. Overall, DC motors continue to provide an alternative to inverter driven AC Motors where motor speed variation is needed. AC A LTERNATOR The basic construction and premise of operation of an AC alternator is similar to a dynamo with the exception of the fact that the commutator is unnecessary and therefore absent. Another salient difference between a dynamo and an AC alternator is that the roles and the properties of the stator and rotor are reversed. In an AC alternator, as shown in Figure 7.4 (a), the magnetic field is produced by the rotating rotor and the stator serves as an armature. The key reason for the armature — the segment of the generator where the generated current and EMF (voltage) are harnessed — to serve as a stationary “exoskeleton” is that large induced currents require robust insulation of the armature windings. In addition, with large currents, larger magnetic forces and torques are in play, which makes it important to secure or anchor the windings in a rugged structure. As with a DC generator, the power in AC alternators is fundamentally produced in sinusoidal form. Since the output of an AC alternator does not need to be rectified to DC form, commutator function is not needed. Construction of a basic AC alternator or generator is shown in Figure 7.4 (a)...
eBook - ePubThe Truth About Tesla
The Myth of the Lone Genius in the History of Innovation
- Christopher Cooper(Author)
- 2018(Publication Date)
- Race Point Publishing(Publisher)
...In the most common motor design, the stator consists of a field magnet with a constant magnetic field, and the rotor is comprised of coils of conductive wire (typically copper or aluminum) and an axle. The conductors that carry the current involved in the transfer of electrical work are also called the armature windings. Commonly, the rotor is the armature. In DC motors or generators, a commutator—used to convert between alternating and direct current—is usually attached to the axle and makes periodic contact with copper brushes attached to the stator. Stator (Field Magnet) The stator is the stationary part of an electric motor. In Tesla’s design, it acts as a field magnet, periodically attracting or repelling the poles of the electrified, spinning armature. Armature The armature is the part of an electrical machine around which conductive coils are wound. In this case, it is the moving part or rotor. The armature carries current, which itself produces a magnetic field. The interaction between the rotor and stator magnetic fields—much like the attractive or repulsive force between two refrigerator magnets—creates a torque that can be used to perform work. Commutator A simple commutator is a pair of plates attached to the axle on the armature. The plates connect the wound coils of the armature with the source of the electromagnetism. As the armature spins, the plates periodically make contact with brushes (usually of copper wire or carbon) attached to the stator. Every time the plates reconnect with the brushes, they reverse the flow of the current. Commutators are only needed for DC machines. DC circuits generally operate with two wires. One carries current from the generator (say, a battery) to whatever device is utilizing the energy (say, a motor). The other wire carries current from the motor back to the generator...
eBook - ePubFundamentals of Electric Machines: A Primer with MATLAB
A Primer with MATLAB
- Warsame Hassan Ali, Matthew N. O. Sadiku, Samir Abood(Authors)
- 2019(Publication Date)
- CRC Press(Publisher)
...It is also characterized by different speeds and the possibility of controlling the speed of rotation, and the possibility of rotation in two directions, and the need for maintenance and no exhaust from them and use electric motors in various devices such as refrigerators, washing machines, vacuum cleaners, mixers, air conditioners, fans, and elevators and many devices. The alternative electric car is a vehicle that contains internal combustion motors that now exist that contribute to environmental pollution by a large amount. 7.1 Single-Phase Motor The electric motors have been used in the operation of various types of modern devices and equipment that emerged with the emergence of these motors such as audio and video recorders, computer drives, printers, games, and industrial robots of uses. The principle of the work of the electric motor is the opposite of the principle of the work of the generator when following an electric current in a wire located within a fixed magnetic field generates mechanical force affect the wire and push it to the movement, and thus could convert electricity to mechanical energy (Figure 7.1). The single-phase electric motors are of many types depending on the nature of their work and design. 1. Induction-motors that decrease in speed with increased load 2. Synchronous motors that do not affect the speed when the load is changed on the axis of rotation 3. General motors (universal-motors). 7.1.1 Induction Motors These machines are the most widely used and used in daily use for household, office, medical, and other purposes, because they are simple in design, low cost, good efficiency, low power, and rotate at different speeds (Figure 7.2). FIGURE 7.1 Different types of single-phase motor. FIGURE 7.2 Single-phase induction motor. 7.1.1.1 Motor Construction These motors consist of major parts. that are present in all types, and additional parts are only present in some of them...
