Electric motors of various sizes.

An electric motor converts electrical energy into mechanical motion. The reverse task, that of converting mechanical motion into electrical energy, is accomplished by a generator or dynamo. In many cases the two devices differ only in their application and minor construction details, and some applications use a single device to fill both roles. For example, traction motors used on locomotives often perform both tasks if the locomotive is equipped with dynamic brakes. Picture I just took for NL wiki as illustration of article on electric motors, I bought these three earlier today :) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Electrical energy or electromagnetic energy is a form of energy present in any electric field or magnetic field, or in any volume containing electromagnetic radiation. ... An electrical generator is a device that produces electrical energy from a mechanical energy source. ... Traction motor typically refers to those motors that are used to power the driving wheels of a railroad locomotive, electrical multi-unit train (such as a subway or light rail vehicle train), or a tram. ... A locomotive (from lat. ... Regenerative braking is any technology which allows a vehicle to recapture and store part of the kinetic energy that would ordinarily be lost when braking. ...

Operation

Most electric motors work by electromagnetism, but motors based on other electromechanical phenomena, such as electrostatic forces and the piezoelectric effect, also exist. The fundamental principle upon which electromagnetic motors are based is that there is a mechanical force on any wire when it is conducting electricity while contained within a magnetic field. The force is described by the Lorentz force law and is perpendicular to both the wire and the magnetic field. In a rotary motor, there is a rotating element, the rotor. The rotor rotates because the wires and magnetic field are arranged so that a torque is developed about the rotor's axis. In physics, magnetism is one of the phenomena by which materials exert an attractive or repulsive force on other materials. ... An electrostatic motor or capacitor motor is a type of electric motor based on the attraction and repulsion of electric charge. ... Piezoelectricity is the ability of certain crystals to produce a voltage when subjected to mechanical stress. ... In physics, the Lorentz force is the force exerted on a charged particle in an electromagnetic field. ... Current flowing through a wire produces a magnetic field (M) around the wire. ...

Most magnetic motors are rotary, but linear types also exist. In a rotary motor, the rotating part (usually on the inside) is called the rotor, and the stationary part is called the stator. The motor contains electromagnets that are wound on a frame. Though this frame is often called the armature, that term is often erroneously applied. Correctly, the armature is that part of the motor across which the input voltage is supplied or that part of the generator across which the output voltage is generated. Depending upon the design of the machine, either the rotor or the stator can serve as the armature. R0t0r is from efnet ... The stator is the fixed part of a rotating machine. ... An electromagnet is a type of magnet in which the magnetic field is produced by a flow of electric current. ... In electrical engineering, an armature is usually the rotating part of an electric motor or dynamo. ... This article may be too technical for most readers to understand. ... Armature is usually the rotating part of an electric motor or dynamo. ...

DC motors

One of the first electromagnetic rotary motors was invented by Michael Faraday in 1821 and consisted of a free-hanging wire dipping into a pool of mercury. A permanent magnet was placed in the middle of the pool. When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a circular magnetic field around the wire. This motor is often demonstrated in school physics classes, but brine is sometimes used in place of the toxic mercury. This is the simplest form of a class of electric motors called homopolar motors. Michael Faraday Michael Faraday (September 22, 1791 – August 25, 1867) was a British scientist (a physicist and chemist) who contributed significantly to the fields of electromagnetism and electrochemistry. ... 1821 was a common year starting on Monday (see link for calendar). ... General Name, Symbol, Number mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12, 6, d Appearance silvery white Atomic mass 200. ... Magnetic lines of force of a bar magnet shown by iron filings on paper A magnet is an object that has a magnetic field. ... In electricity, current refers to electric current, which is the flow of electric charge. ... Brine is water saturated or nearly saturated with salt. ... A homopolar motor is of essentially the same construction as a homopolar generator, in general called a homopolar machine. ...

The modern DC motor was invented by accident in 1873, when Zénobe Gramme connected a spinning dynamo to a second similar unit, driving it as a motor. Zénobe Gramme, by Mathurin Moreau Zénobe Théophile Gramme (April 4, 1826 - January 20, 1901) was a Belgian electrical engineer. ... Dynamo can refer to more than one item. ...

The classic DC motor has a rotating armature in the form of an electromagnet with two poles. A rotary switch called a commutator reverses the direction of the electric current twice every cycle, to flow through the armature so that the poles of the electromagnet push and pull against the permanent magnets on the outside of the motor. As the poles of the armature electromagnet pass the poles of the permanent magnets, the commutator reverses the polarity of the armature electromagnet. During that instant of switching polarity, inertia keeps the classical motor going in the proper direction. (See the diagrams below.) Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... A commutator is an electrical switch that periodically reverses the current in an electric motor or electrical generator. ... In electrical engineering, an armature is usually the rotating part of an electric motor or dynamo. ... In psychology, social inertia describes a persons resistance to change. ...

A simple DC electric motor. When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation.

The armature continues to rotate.

When the armature becomes horizontally aligned, the commutator reverses the direction of current through the coil, reversing the magnetic field. The process then repeats.

Here is an internal view of a d. ... Here is an internal view of a d. ... Illustration of a simple electric motor. ... Illustration of a simple electric motor. ... Illustration of a simple electric motor. ... Illustration of a simple electric motor. ...

DC motor speed generally depends on a combination of the voltage and current flowing in the motor coils and the motor load or braking torque. The speed of the motor is proportional to the voltage, and the torque is proportional to the current. The speed is typically controlled by altering the voltage or current flow by using taps in the motor windings or by having a variable voltage supply. In physics, torque can be thought of informally as rotational force. Torque is measured in units of newton metres. ...

As this type of motor can develop quite high torque at low speed it is often used in traction applications such as locomotives. A locomotive (from lat. ...

However, there are a number of limitations in the classic design, many due to the need for brushes to rub against the commutator. The rubbing creates friction, and the higher the speed, the harder the brushes have to press to maintain good contact. Not only does this friction make the motor noisy, but it also creates an upper limit on the speed and causes the brushes eventually to wear out and to require replacement. The imperfect electric contact also causes electrical noise in the attached circuit. These problems vanish when you turn the motor inside out, putting the permanent magnets on the inside and the coils on the outside thus designing out the need for brushes in a brushless design. However such designs need electronic circuits to control the switching of the electromagnets (the function that is performed in conventional motors by the commutator). In physics, friction is the non-conservative resistive force that occurs when two surfaces travel along each other when forced together. ... ... A brushless DC motor (BLDC) is a DC electric motor that uses an electronically-controlled commutation system, instead of a mechanical commutation system. ...

Wound field DC motor

The permanent magnets on the outside (stator) of a DC motor may be replaced by electromagnets. By varying the field current it is possible to alter the speed/torque ratio of the motor. Typically the field winding will be placed in series (series wound) with the armature winding to get a high torque low speed motor, in parallel (shunt wound) with the armature to get a high speed low torque motor, or to have a winding partly in parallel, and partly in series (compound wound) for a balance. Further reductions in field current are possible to gain even higher speed but correspondingly lower torque. This technique is ideal for electric traction (see Traction motor) and many similar applications where its use can eliminate the requirement for a mechanically variable transmission. The stator is the fixed part of a rotating machine. ... Traction motor typically refers to those motors that are used to power the driving wheels of a railroad locomotive, electrical multi-unit train (such as a subway or light rail vehicle train), or a tram. ...

Universal motors

A variant of the wound field DC motor is the universal motor. The name derives from the fact that it may use AC or DC supply current, although in practice they are nearly always used with AC supplies. The principle is that in a wound field DC motor the current in both the field and the armature (and hence the resultant magnetic fields) will alternate (reverse polarity) at the same time, and hence the mechanical force generated is always the same. In practice the motor must be specially designed to cope with the AC current (impedance/reluctance must be taken into account), and the resultant motor is generally less efficient than an equivalent pure DC motor. The advantage of the universal motor is that AC supplies may be used on motors which have the typical characteristics of DC motors, specifically high starting torque and very compact design if high running speeds are used. The negative aspect is the maintenance and reliability problems caused by the commutator, and as a result such motors will rarely be found in industry but are the most common type of AC supplied motor in devices such as food mixers and power tools which are only used intermittently. Continuous speed control of a universal motor running on AC is very easily accomplished using a thyristor circuit while stepped speed control can be accomplished using multiple taps on the field coil. Household blenders that advertise many speeds frequently combine a field coil with several taps and a diode that can be inserted in series with the motor (causing the motor to run on half-wave DC with half the RMS voltage of the AC power line). In electrical engineering, Impedance is a measure of opposition to a sinusoidal electric current. ... Magnetic reluctance is the resistance of a material to a magnetic field. ... A commutator is an electrical switch that periodically reverses the current in an electric motor or electrical generator. ... Circuit symbol for a thyristor The thyristor is a solid-state semiconductor device similar to a diode, with an extra terminal which is used to turn it on. ... RMS may mean: root mean square, a concept in statistics and electronics Richard M. Stallman, a computer programmer and founder of the GNU project. ...

Unlike the other common forms of AC motors (induction motors and synchronous motors), universal motors can easily exceed one revolution per cycle of the mains current (that is, exceed 3000 rpm on a 50 Hz system or 3600 rpm on a 60 Hz system). This makes them especially useful for certain appliances such as blenders, vacuum cleaners, and hair dryers where high-speed operation is desired. rpm or RPM may mean: revolutions per minute RPM Package Manager (originally called Red Hat Package Manager) RPM (movie) RPM (band), a Brazilian rock band RPM (magazine), a former Canadian music industry magazine In firearms, Rounds Per Minute: how many shots an automatic weapon can fire in one minute On... The hertz (symbol Hz) is the SI unit of frequency. ... The word blender has a number of meanings: A blender is a common kitchen appliance for chopping or liquefying food. ... Canister vacuum cleaner A vacuum cleaner is a device that uses an air pump to create a partial vacuum to suck up dust and dirt, usually from carpeted floors. ... Categories: Stub | Hairdressing ...

With the very low cost of semiconductor rectifiers, some applications that would have previously used a universal motor now use a pure DC motor, usually with a permanent magnet field. This is especially true if the semiconductor circuit is also used for variable-speed control. A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devcices (such as diodes) arranged for converting alternating current to continuous current. ...

AC motors

A typical AC motor consists of two parts:

1. An outside stationary stator having coils supplied with AC current to produce a rotating magnetic field, and;
2. An inside rotor attached to the output shaft that is given a torque by the rotating field.

There are two fundamental types of AC motor depending on the type of rotor used:

• The synchronous motor, which rotates exactly at the supply frequency or a submultiple of the supply frequency, and;
• The induction motor, which turns slightly slower, and typically (though not necessarily always) takes the form of the squirrel cage motor.

The rotating magnetic field principle, though commonly credited to Nikola Tesla in 1882 or thereabouts, was productively employed by mainstream scientists such as Michael Faraday and James Clerk Maxwell in the 1820s. Tesla, however, exploited the principle to design a unique two-phase induction motor in 1883. Michael von Dolivo-Dobrowlsky invented the first modern three-phase "cage-rotor" in 1890. Introduction of the motor from 1888 onwards initiated what is known as the Second Industrial Revolution, making possible the efficient generation and long distance distribution of electrical energy using the alternating current transmission system, also of Tesla's invention (1888)[1]. The first successful commercial three phase generation and long distance transmission system was designed by Almerian Decker at Mill Creek No. 1 [2] in Redlands California.[3] A squirrel cage rotor is the rotating part commonly used in an AC induction motor. ... Nikola Tesla (July 10, 1856 – c. ... 1882 was a common year starting on Sunday (see link for calendar). ... Michael Faraday Michael Faraday (September 22, 1791 – August 25, 1867) was a British scientist (a physicist and chemist) who contributed significantly to the fields of electromagnetism and electrochemistry. ... James Clerk Maxwell (June 13, 1831–November 5, 1879) was a Scottish mathematical physicist, born in Edinburgh. ... The Second Industrial Revolution (1871-1914) involved significant developments for society and the world. ...

Although the statement that "AC motors generally come in two types: single phase and three phase" is often made, this distinction is of insufficient importance to assign the term "types." What is actually meant is that, for more important purposes of commercial power distribution, AC motors are commonly employed in a "three-phase" system whereby three discrete waveforms--each logically displaced 120 degrees from its neighbor--are transmitted in unison. It is common for an individual subscriber to have only one of these phases actually present on the premises, allowing only single phase motors to be used. city lights viewed in a motion blurred exposure. ... The generation of AC electric power is commonly three phase, in which the waveforms of three supply conductors are offset from one another by 120°. These three conductors are commonly housed in a single conduit (e. ... Three-phase systems have 3 waveforms (usually carrying power) that are 2Ï€/3 radians (120°,1/3 of a cycle) offset in time. ...

Three-phase AC induction motors

For higher-power applications where a polyphase electrical supply is available, the three-phase (or polyphase) AC induction motor is used. The phase differences between the three phases of the polyphase electrical supply create a rotating electromagnetic field in the motor. Three phase systems have 3 waveforms (usually carrying power) that are 2/3π radians (120 degrees,1/3 of a cycle) offset in time. ... Polyphase electrical systems supply alternating current electrical power in overlapping phases. ...

Through electromagnetic induction, the rotating magnetic field induces a current in the conductors in the rotor, which in turn sets up a counterbalancing magnetic field that causes the rotor to turn in the direction the field is rotating. The rotor must always rotate slower than the rotating magnetic field produced by the polyphase electrical supply; otherwise, no counterbalancing field will be produced in the rotor. Electromagnetic induction is the production of an electrical potential difference (or voltage) across a conductor situated in a changing magnetic flux. ...

Induction motors are the workhorses of industry and motors up to about 500 kW in output are produced in highly standardized frame sizes, making them nearly completely interchangeable between manufacturers (although European and North American standard dimensions are of course different).

There are two types of rotors used in induction motors. Most use the squirrel cage rotor. An alternate design, called the wound rotor, is used when variable speed is required. In this case, the rotor has the same number of poles as the stator and the windings are made of wire, connected to slip rings on the shaft. Carbon brushes connect the slip rings to an external controller such as a variable resistor that allows changing the motor's slip rate. In certain high-power variable speed wound-rotor drives, the slip-frequency energy is captured, rectified and returned to the power supply through an inverter.

Compared to squirrel cage rotors, wound rotor motors are expensive and require maintenance of the slip rings and brushes, but they were the standard form for variable speed control before the advent of compact power electronic devices. Transistorized inverters with variable frequency drive can now be used for speed control and wound rotor motors are becoming less common. (Transistorized inverter drives also allow the more-efficient three-phase motors to be used when only single-phase mains current is available.)

Several methods of starting a polyphase motor are used. Where the large inrush current and high starting torque can be permitted, the motor can be started across the line, by applying full line voltage to the terminals. Where it is necessary to limit the starting inrush current (where the motor is large compared with the short-circuit capacity of the supply), reduced voltage starting using either series inductors, an autotransformer, thyristors, or other devices are used. A technique sometimes used is star-delta starting, where the motor coils are initially connected in wye for acceleration of the load, then switched to delta when the load is up to speed. Transistorized drives can directly vary the applied voltage as required by the starting characteristics of the motor and load. 13. ... Circuit symbol for a thyristor The thyristor is a solid-state semiconductor device similar to a diode, with an extra terminal which is used to turn it on. ...

This type of motor is becoming more common in traction applications such as locomotives, where it is known as the asynchronous traction motor. Traction motor typically refers to those motors that are used to power the driving wheels of a railroad locomotive, electrical multi-unit train (such as a subway or light rail vehicle train), or a tram. ...

The speed of the AC motor is determined primarily by the frequency of the AC supply and the number of poles in the stator winding, according to the relation:

N_s = 120F / p

where

N_s = Synchronous speed, in revolutions per minute

F = AC power frequency

p = Number of poles, usually an even number but always a multiple of the number of phases

Actual RPM for an induction motor will be less than this calculated synchronous speed by an amount known as slip that increases with the torque produced. With no load the speed will be very close to synchronous. When loaded, standard motors have between 2-3% slip, special motors may have up to 7% slip, and a class of motors known as torque motors are rated to operate at 100% slip (0 RPM/full stall).

The slip of the AC motor is calculated by:

S = (N_s − Nr) / N_s

where

N_r = Rotational speed, in revolutions per minute.

S = Slip, in percent.

As an example, a typical four-pole motor running on 60 Hz might have a nameplate rating of 1725 RPM at full load, while its calculated speed is 1800.

The speed in this type of motor has traditionally been altered by having additional sets of coils or poles in the motor that can be switched on and off to change the speed of magnetic field rotation. However, developments in power electronics mean that the frequency of the power supply can also now be varied to provide a smoother control of the motor speed. Power electronics is the technology associated with the efficient conversion, control and conditioning of electric power by static means from its available input form into the desired electrical output form. ...

Three-phase AC synchronous motors

If connections to the rotor coils of a three-phase motor are taken out on slip-rings and fed a separate field current to create a continuous magnetic field (or if the rotor consists of a permanent magnet), the result is called a synchronous motor because the rotor will rotate in synchronism with the rotating magnetic field produced by the polyphase electrical supply.

A synchronous motor can also be used as an alternator. An alternator is an electrical generator that converts mechanical energy to alternating current electrical energy. ...

Nowadays, synchronous motors are frequently driven by transistorized variable frequency drives. This greatly eases the problem of starting the massive rotor of a large synchronous motor. They may also be started as induction motors using a squirrel-cage winding that shares the common rotor: once the motor reaches synchronous speed, no current is induced in the squirrel-cage winding so it has little effect on the synchronous operation of the motor. Small Variable Frequency Drive (VFD) A Variable Frequency Drive (sometimes abbreviated VFD) is system for controlling the rotational speed of an alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor. ...

Synchronous motors are occasionally used as traction motors; the TGV may be the best-known example of such use. TGV trains depart from Gare Montparnasse in Paris to western and south-western destinations. ...

Single-phase AC induction motors

A polyphase induction motor will continue to rotate even if one phase is disconnected, at reduced torque. However, a polyphase motor at standstill will not generate any net starting torque if connected only to a single-phase supply. The key to the design of single-phase motors, then, is to provide a rotating magnetic field to produce starting torque.

A common single-phase motor is the shaded pole motor, which is used in devices requiring lower torque, such as electric fans or other small household appliances. In this motor, small single-turn copper "shading coils" create the moving magnetic field. Part of each pole is encircled by a copper coil or strap; the induced current in the strap opposes the change of flux through the coil (Lenz's Law), so that the maximum field intensity moves across the pole face on each cycle. small shaded-pole motor shading-coils A Shaded pole motor is a type of AC single phase induction motor. ... In physics, torque can be thought of informally as rotational force. Torque is measured in units of newton metres. ... Household Electric Fan A fan has two purposes. ... // Introduction Lenzs law lent-səz-lä [In German, z has the phonetic sound of ts] was formulated by German physicist Heinrich Lenz and gives the direction of the induced emf resulting from electromagnetic induction, thus: Definition (who cares about that german bulllshiiitt up there. ...

Another common single-phase AC motor is the split-phase induction motor, commonly used in major appliances such as washing machines and clothes dryers. Compared to the shaded pole motor, these motors can generally provide much greater starting torque by using a special startup winding in conjunction with a centrifugal switch. A major appliance is a large machine which accomplishes some routine housekeeping task, which includes purposes such as cooking, food preservation, or cleaning, whether in a household, institutional, commercial or industrial setting. ... Washing Machine is an album by the band Sonic Youth. ... A dryer or drier most commonly means: a clothes dryer / tumble-dryer a hair dryer There are also various industrial dryers for everything from wet paper to candy. ... A startup winding, also known as the auxiliary winding, is used to create the torque needed to start a single phase induction motor. ... A centrifugal switch is an electric switch that operates using the centrifugal force created from a rotating shaft, most commonly that of an electric motor or gasoline engine. ...

In the split phase motor, the startup winding is designed with a higher resistance than the running winding. This creates an LR circuit which slightly shifts the phase of the current in the startup winding. When the motor is starting, the startup winding is connected to the power source via a set of spring-loaded contacts pressed upon by the not-yet-rotating centrifugal switch. The starting winding is wound with fewer turns of smaller wire than the main winding, so it has a higher resistance. The extra resistance creates a small phase shift, not more than about 30 degrees, between the flux due to the main winding and the flux of the starting winding. The starting direction of rotation may be reversed simply by exchanging the connections of the startup winding relative to the running winding. A split phase electricity distribution system is a 3-wire single-phase distribution system, commonly used in North America for single-family residential and light commercial (up to about 100 kVA) applications. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ...

The phase of the magnetic field in this startup winding is shifted from the phase of the mains power, allowing the creation of a moving magnetic field which starts the motor. Once the motor reaches near design operating speed, the centrifugal switch activates, opening the contacts and disconnecting the startup winding from the power source. The motor then operates solely on the running winding. The starting winding must be disconnected since it would increase the losses in the motor.

In a capacitor start motor, a starting capacitor is inserted in series with the startup winding, creating an LC circuit which is capable of a much greater phase shift (and so, a much greater starting torque). The capacitor naturally adds expense to such motors. A capacitor is a device that stores energy in the electric field created between a pair of conductors on which equal but opposite electric charges have been placed. ... An LC circuit consists of an inductor and a capacitor. ...

Another variation is the Permanent Split-Capacitor (PSC) motor. This motor operates similarly to the capacitor-start motor described above, but there is no centrifugal starting switch and the second winding is permanently connected to the power source. PSC motors are frequently used in air handlers, fans, and blowers and other cases where a variable speed is desired. By changing taps on the running winding but keeping the load constant, the motor can be made to run at different speeds.

Single-phase AC synchronous motors

Small single-phase AC motors can also be designed with magnetized rotors (or several variations on that idea). The rotors in these motors do not require any induced current so they do not slip backward against the mains frequency. Instead, they rotate synchronously with the mains frequency. Because of their highly accurate speed, such motors are usually used to power mechanical clocks, audio turntables, and tape drives; formerly they were also much used in accurate timing instruments such as strip-chart recorders or telescope drive mechanisms. The shaded-pole synchronous motor is one version. A turntable is any rotating platform: a phonograph (or the platter of), used to play vinyl records, or by DJs to mix or scratch them (see turntablism) a device used at some railroad facilities to turn a locomotive or other rolling stock around, or onto one of several radially arranged... A tape drive, also known as a streamer, is a peripheral device that reads and writes data stored on a magnetic tape or a punched tape. ... shading-coils within the magnetic circuit of the field coil Shaded-pole synchronous motors are a class of AC motor. ...

Because inertia makes it difficult to instantly accelerate the rotor from stopped to synchronous speed, these motors normally require some sort of special feature to get started. Various designs use a small induction motor (which may share the same field coils and rotor as the synchronous motor) or a very light rotor with a one-way mechanism (to ensure that the rotor starts in the "forward" direction). In psychology, social inertia describes a persons resistance to change. ...

Stepper motors

Closely related in design to three-phase AC synchronous motors are stepper motors, where an internal rotor containing permanent magnets or a large iron core with salient poles is controlled by a set of external magnets that are switched electronically. A stepper motor may also be thought of as a cross between a DC electric motor and a solenoid. As each coil is energized in turn, the rotor aligns itself with the magnetic field produced by the energized field winding. Unlike a synchronous motor, in its application, the motor may not rotate continuously; instead, it "steps" from one position to the next as field windings are energized and deenergized in sequence. Depending on the sequence, the rotor may turn forwards or backwards. The top electromagnet (1) is charged, attracting the topmost four teeth of a sprocket. ... wound around a movable steel or iron slug (termed the armature). ...

Simple stepper motor drivers entirely energize or entirely deenergize the field windings, leading the rotor to "cog" to a limited number of positions; more sophisticated drivers can proportionally control the power to the field windings allowing the rotors to position "between" the "cog" points and thereby rotate extremely smoothly. Computer controlled stepper motors are one of the most versatile forms of positioning systems, particularly when part of a digital servo-controlled system. Cog is a term with several meanings: A part of a gear system A small sailing vessel called a cog (ship) A tenon that extends all the way through another piece of wood, in joinery The evil robots in Toontown Online COG is also an acronym for: Center of gravity... Small R/C servo mechanism 1. ...

Brushless DC motors

Midway between ordinary DC motors and stepper motors lies the realm of the brushless DC motor. Built in a fashion very similar to stepper motors, these often use a permanent magnet external rotor, three phases of driving coils, one or more Hall effect devices to sense the position of the rotor, and the associated drive electronics. The coils are activated, one phase after the other, by the drive electronics as cued by the signals from the Hall effect sensors. In effect, they act as three-phase synchronous motors containing their own variable frequency drive electronics. DC may stand for: Augustin Pyrame de Candolle in binomial nomenclature Axiom of dependent choice, in set theory (mathematics) Da capo, a musical term DC Comics, a comic book publisher whose name is derived from one of its flagship titles, Detective Comics DC Shoes, a skateboarding apparel manafacturer Democrazia Cristiana... A brushless DC motor (BLDC) is a DC electric motor that uses an electronically-controlled commutation system, instead of a mechanical commutation system. ... Hall effect diagram, showing electron flow (rather than conventional current). ... Small Variable Frequency Drive (VFD) A Variable Frequency Drive (sometimes abbreviated VFD) is system for controlling the rotational speed of an alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor. ...

Brushless DC motors are commonly used to drive fans, the spindles within CD, CD-ROM (etc.) drives, and mechanisms within office products such as laser printers and photocopiers. They also find significant use in high-performance electric model aircraft. They have several advantages over conventional motors: Fan can mean the following: enthusiast or fanatic air-movement device This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... CD may stand for: Compact Disc Canadian Forces Decoration Cash Dispenser (at least used in Japan) CD LPMud Driver Centrum-Demokraterne (Centre Democrats of Denmark) Certificate of Deposit ÄŒeské Dráhy (Czech Railways) Chad (NATO country code) Chalmers Datorförening (computer club of the Chalmers University of Technology) a 1960s... The CD-ROM (an abbreviation for Compact Disc Read-Only Memory (ROM)) is a non-volatile optical data storage medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive. ... Laser printer A laser printer is a common type of computer printer that produces high quality printing, and is able to produce both text and graphics. ... A small, much-used Xerox copier in a high school library. ...

• Compared to AC fans using shaded-pole motors, they are very efficient, running much cooler than the equivalent AC motors. This cool operation leads to much-improved life of the fan's bearings.
• Without a commutator to wear out, the life of a DC brushless motor can be significantly longer compared to a DC motor using brushes and a commutator
• The same Hall effect devices that provide the commutation can also provide a convenient tachometer signal for closed-loop control (servo-controlled) applications. In fans, the tachometer signal can be used to derive a "fan okay" signal.
• The motor can be easily synchronized to an internal or external clock, leading to precise speed control.

Modern DC brushless motors range in power from a fraction of a watt to many kilowatts. Bearing is the following: Often, bearing is the state of having something as a quality, characteristic, or permanent attribute. ... A commutator is an electrical switch that periodically reverses the current in an electric motor or electrical generator. ... A tachometer is a device used for measuring the speed of a moving body or substance (from Greek: tachos = speed, metron = measure). ... The watt (symbol: W) is the SI derived unit of power. ...

Coreless DC motors

A coreless DC motor is a specialized form of an ordinary DC motor. Optimized for rapid acceleration, these motors have a rotor that is constructed without any iron core. The rotor can take the form of a winding-filled cylinder inside the stator magnets, a basket surrounding the stator magnets, or a flat pancake (possibly formed on a printed wiring board) running between upper and lower stator magnets. The windings are typically stabilized by being impregnated with epoxy resins. Acceleration is the time rate of change of velocity, and at any point on a v-t graph, it is given by the gradient of the tangent to that point In physics, acceleration (symbol: a) is defined as the rate of change (or time derivative) of velocity. ... Close-up photo of one side of a motherboard PCB, showing conductive traces, vias and solder points for through-hole components on the opposite side. ... Epoxy or polyepoxide is a thermosetting epoxide polymer that cures when mixed with a catalyzing agent or hardener. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. The first commercial attempts to prepare resins from epichlorohydrin occurred in 1927 in the United States. ...

Because the rotor is much lighter in weight (mass) than a conventional rotor formed from copper windings on steel laminations, the rotor can accelerate much more rapidly, often achieving a mechanical time constant under 1 ms. This is especially true if the windings use aluminum rather than the heavier copper. But because there is no metal mass in the rotor to act as a heat sink, even small coreless motors must often be cooled by forced air. Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic brown Atomic mass 63. ... The old steel cable of a colliery winding tower Steel is a metal alloy whose major component is iron, with carbon being the primary alloying material. ... In physics and engineering, the time constant, usually denoted by the Greek letter Ï„ (tau), characterizes the frequency response of a first-order, linear time-invariant (LTI) system. ... A millisecond is an SI-derived unit of time, equal to one thousandth of a second. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ...

These motors were commonly used to drive the capstan(s) of magnetic tape drives and are still widely used in high-performance servo-controlled systems. Nautical capstan A capstan is a rotating machine used to control or apply force to another element, usually linear. ... Magnetic tape is a non-volatile storage medium consisting of a magnetic coating on a thin plastic strip. ...

Linear motors

A linear motor is essentially an electric motor that has been "unrolled" so that instead of producing a torque (rotation), it produces a linear force along its length by setting up a traveling electromagnetic field. A linear motor is essentially an electric motor that has had its stator unrolled so that instead of producing a torque (rotation), it produces a linear force along its length. ... In physics, torque can be thought of informally as rotational force. Torque is measured in units of newton metres. ...

Linear motors are most commonly induction motors or stepper motors. You can find a linear motor in a maglev (Transrapid) train, where the train "flies" over the ground. Maglev can refer to General Magnetic levitation Magnetic levitation trains This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Transrapid at the Emsland test facility Transrapid is a German monorail system using magnetic levitation. ...

See also

Wikibooks has more about this subject:

School science how-to

Components: Wikipedia does not have an article with this exact name. ...

• Centrifugal switch
• Commutator (electric)
• Slip ring

Scientists and engineers: A centrifugal switch is an electric switch that operates using the centrifugal force created from a rotating shaft, most commonly that of an electric motor or gasoline engine. ... A commutator is an electrical switch that periodically reverses the current in an electric motor or electrical generator. ... One or more images would improve this articles quality. ...

• Thomas Edison
• Frank J. Sprague
• Nikola Tesla
• George Westinghouse

Applications: Thomas Alva Edison Thomas Alva Edison (February 11, 1847 – October 18, 1931) was an inventor and businessman who developed many important devices. ... Frank Julian Sprague (1857-1934) American inventor, Father of Electric Traction Frank Julian Sprague (1857–1934) was an American naval officer and inventor who contributed to the development of the electric motor, electric railways, and electric elevators. ... Nikola Tesla (July 10, 1856 – c. ... George Westinghouse (October 6, 1846 – March 12, 1914) was an American entrepreneur and engineer now best known for the brand of electrical goods that bear his name. ...

• Table saw
• Electric vehicle
• Power factor correction

Other: Powermatic® Model 1660791K 5 HP Cabinet Table Saw Bosch Model 4000-46 10 Bench Table Saw Laguna Tools TSS Sliding Tablesaw A table saw or sawbench is the most common piece of large woodworking equipment. ... An electric vehicle is a vehicle whose motion is provided by electric motors. ... Power factor correction (PFC) is a technique of counteracting the undesirable effects of electric loads that create a power factor (p. ...

• Electrical element
• Electrical generator
• List of electronics topics
• List of technologies
• Maximum power theorem
• Motor
• Motor-generator
• Motor controller
• Propulsion method
• Single phase electric power
• Timeline of motor and engine technology

Hi!... ... An electrical generator is a device that produces electrical energy from a mechanical energy source. ... This is a list of communications, computers, electronic circuits, fiberoptics, microelectronics, medical electronics, reliablity, and semiconductors. ... This is a list of technologies Early or prehistoric advances in technology or fundamental tools Agriculture Astronomy Animal husbandry Cooking Clothing Fire Inclined plane Lever Mining Pottery Pulley Screw Weaponry Wedge Wheel Writing Modern major fields of technology Life science Agriculture Biotechnology Genetic engineering Medicine Domestic technology Further technology items... This article contains information that is not verifiable. ... A motor is a device that converts energy into mechanical power, and is often synonymous with engine. ... A motor-generator (an M-G set) is a device for converting one form of electrical power to another form. ... A motor controller is a device or group of devices that serves to govern in some predetermined manner the performance of an electric motor. ... Propulsion method may refer to a number of different articles: For a list of space propulsion methods, see spacecraft propulsion. ... The generation of AC electric power is commonly three phase, in which the waveforms of three supply conductors are offset from one another by 120°. These three conductors are commonly housed in a single conduit (e. ... Timeline of motor and engine technology 1698 - Thomas Savery builds a steam-powered water pump for pumping water out of mines 1712 - Thomas Newcomen builds a piston-and-cylinder steam-powered water pump for pumping water out of mines 1769 - James Watt patents his first improved steam engine 1816 - Robert...

Textbooks

• Shanefield D. J., Industrial Electronics for Engineers, Chemists, and Technicians, William Andrew Publishing, Norwich, NY, 2001. A self-teaching textbook that briefly covers electric motors, transformers, speed controllers, wiring codes and grounding, transistors, digital, etc. Easy to read and understand, up to an elementary level on each subject, not a suitable reference book for technologists already working in any of those fields.

• Woodsom and Melcher, unnamed book, for graduates
• Fitzgerald/Kingsley/Kusko (Fitzgerald/Kingsley/Umans in later years), Electric Machinery, classic text for junior and senior electrical engineering students. Originally published in 1952, 6th edition published in 2002. Authors still listed as Fitzgerald/Kingsley/Umans although Fitzgerald and Kingsley are now deceased.
• Slemon and Straughen, unnamed book, less advanced
• Van E. Mablekos, title unknown, very easy reading
• Bedford and Hoft, unnamed book on power electronics, outdated Principles of Inverter Circuits (1964); John Wiley & Sons (Inverter circuits are used for adjustable frequency motor speed control)
• Dewan and Straughen, another unnamed book on power electronics
• B. R. Pelly, "Thyristor Phase-Controlled Converters and Cycloconverters: Operation, Control, and Performance" (New York: John Wiley, 1971).

Assorted transistors Transistor was also a common name for a 1960s era handheld transistor radio. ...

References

Donald G. Fink and H. Wayne Beaty, Standard Handbook for Electrical Engineers, Eleventh Edition, McGraw-Hill, New York, 1978, ISBN 007020974X.