Physics
Linear Motor
A linear motor is a type of electric motor that produces motion in a straight line, as opposed to the rotational motion produced by traditional motors. It consists of a moving part (the "slider") and a stationary part (the "stator") that generates a magnetic field to propel the slider. Linear motors are used in various applications, including transportation systems, industrial automation, and robotics.
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4 Key excerpts on "Linear Motor"
eBook - PDF- Charles A. Gross(Author)
- 2006(Publication Date)
- CRC Press(Publisher)
Advances in power electronics, superconducting magnets, and control theory have brought transla-tional machines into prominence, particularly for transportation applications. There are many applications for linear machines, including: ● Railguns and catapults. It is possible to achieve enormous accelerations (100 g ), and extremely high velocity (in excess of 1000m/s) in very short distances. The kinetic energies are sufficient to make the technology viable for weapon systems. Likewise, EM catapult technology is practical for launching aircraft from aircraft carriers. ● Textile machines . Looms and weaving machines applications require high-speed precision-controlled linear motion, making them an ideal match with Linear Motors. ● Moving sidewalks and escalators. ● High-speed rail (HSR). Above certain speeds, bearing and wheel design is increas-ingly costly and complicated. Linear machines, when combined with magnetic levitation, provide a viable technology. ● Linear induction pumps. It can be used to pump liquid metals, such as sodium, bis-muth, and molten steel. ● Automotive collision test facilities . Linear Motors provide excellent drivers for achieving precise acceleration and velocity-controlled experiments. 372 Electric Machines ● High performance amusement park rides. A particular favorite of my granddaugh-ters Jenny and Robyn (see Figure 10.1). ● Elevators . Can be powered with Linear Motors, particularly attractive for so-called ropeless designs, which are necessary in extremely tall buildings. The Japanese Handbook of Linear Motor Applications lists over 50 applications for linear machines. All of the basic rotational machines have their translational equivalents. We focus on two of these: ● the linear induction machine (LIM), ● the linear synchronous machine (LSM). We start our study by examining the details of LIM construction. FIGURE 10.1. A LIM driven coaster ride. Photo by Theme Park Review, www.themeparkreview.com.
eBook - PDFMechatronics
A Foundation Course
- Clarence W. de Silva(Author)
- 2010(Publication Date)
- CRC Press(Publisher)
The pertinent constitutive equations in the general and linear cases are given as well in the figures. 3.6.4.4.1 DC Motor The dc motor is a commonly used electrical actuator. It converts dc electrical energy into mechanical energy. The principle of operation is based on the fact that when a conductor carrying current is placed in a magnetic field, a force is generated (Lorentz’s law). It is this force that results from the interaction of two magnetic fields, which is presented as the magnetic torque in the rotor of the motor. A dc motor has a stator and a rotor (armature) with windings that are excited by a field voltage v f and an armature voltage v a , respectively. The equivalent circuit of a dc motor is shown in Figure 3.23a, where the field circuit and the armature circuit are shown sepa-rately, with the corresponding supply voltages. This is the separately excited case. If the stator filed is provided by a permanent magnet, then the stator circuit that is shown in Figure 3.23a is simply an equivalent circuit, where the stator current i f can be assumed constant. Similarly, if the rotor is a permanent magnet, what is shown in Figure 3.23a is an + – , i i v i i 0 , v 0 ( t ) v 0 = f ( v i ) v 0 = kv i (Linear amplifier) (a) i i , v i i 0 ( t ), v 0 i 0 = f ( i i ) i 0 = ki i (Linear amplifier) (b) FIGURE 3.22 Linear graph representation of: (a) An across-variable amplifier ( A -type amplifier); (b) a through-variable ampli-fier ( T -type amplifier). Modeling of Mechatronic Systems 141 equivalent circuit where the armature current i a can be assumed constant. The magnetic torque of the motor is generated by the interaction of the stator field (proportional to i f ) and the rotor field (proportional to i a ) and is given by m f a T ki i = (3.30) A back-electromotive force (back e.m.f) is generated in the rotor (armature) windings to oppose its rotation when these windings rotate in the magnetic field of the stator (Lenz’s law).
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
The physical principle of production of mechanical force by the interactions of an electric current and a magnetic field was known as early as 1821. Electric motors of increasing efficiency were constructed throughout the 19th century, but commercial exploitation of electric motors on a large scale required efficient electrical generators and electrical distribution networks. Some devices, such as magnetic solenoids and loudspeakers, although they generate some mechanical power, are not generally referred to as electric motors, and are usually termed actuators and transducers, respectively. ________________________ WORLD TECHNOLOGIES ________________________ History and development Faraday's Electromagnetic experiment, 1821 The principle The conversion of electrical energy into mechanical energy by a electromagnetic means was demonstrated by the British scientist Michael Faraday in 1821. A free-hanging wire was dipped into a pool of mercury, on which a permanent magnet was placed. When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a close circular magnetic field around the wire. This motor is often demonstrated in school physics classes, but brine (salt water) is sometimes used in place of the toxic mercury. This is the simplest form of a class of devices called homopolar motors. A later refinement is the Barlow's Wheel. These were demonstration devices only, unsuited to practical applications due to their primitive construction. ________________________ WORLD TECHNOLOGIES ________________________ Jedlik's electromagnetic self-rotor, 1827. (Museum of Applied Arts, Budapest. The historic motor still works perfectly today.) In 1827, Hungarian Ányos Jedlik started experimenting with electromagnetic rotating devices he called electromagnetic self-rotors.
eBook - PDFElectric Machines and Drives
Principles, Control, Modeling, and Simulation
- Shaahin Filizadeh(Author)
- 2013(Publication Date)
- CRC Press(Publisher)
1 1 Physics of Electric Machines 1.1 Introduction Electric machines are devices used for energy conversion, mostly between mechanical and electrical forms. An electric motor is a machine that con- verts the electrical energy given to it as input to mechanical energy output; a generator does the reverse by producing electrical energy from mechanical energy input. Study of electric machines, therefore, requires knowledge and understanding of the principles of energy conversion. Electric machines come in a wide variety of forms and sizes and are used in markedly different ways and applications. Consider, on the one hand, a small electric motor that rotates and precisely positions a compact disk in a CD drive and, on the other hand, a massive generator in a power plant that is driven by a turbine and generates large amounts of electricity. Despite such apparent differences in scale and application, all electric machines operate on the same underlying principles and share a simple backbone, which is a magnetic medium that links the electrical and mechanical ends of a machine. Apart from its function of facilitating generation and directing magnetic flux to link machine windings, an electromagnetic medium also enables and facilitates the conversion and flow of energy between the two ends of a rotat- ing electric machine, that is, its electrical and mechanical ends. Proper study of a rotating electric machine will therefore entail consideration of its mag- netic structure and its role in the process of energy conversion. Although the study of electromagnetic systems is often associated with vector calculus of Maxwell’s equations, it is indeed possible to describe and understand the behavior of electric machines in simple terms without recourse to compli- cated mathematics. The intention of this chapter is to establish a foundation for understanding the operation of rotating electric machines using simple laws of physics.
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