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Induction motor

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Gear Motors with a motor capacity range from 40W to 90W Right-angle shaft type hypoid motor mini series All models use aluminum frame motors and The AC Series manufactured by Mini Motor is a three- phase AC coaxial geared motor that comes with 2 to 4 poles that are totally enclosed and well ventilated.

Single - phase and three- phase motors from 34 to W. Inline Helical Geared Motors. Single - phase and three- phase motors from 9 to 74 W USA: Inline Helical Geared Motors Single - phase and three- phase motors from 34 to W USA: Single - phase and three- phase motors till 20 W.

Centre distance 20 mm USA: ISM forms the input module that has a solid shaft and BSM module with a back-stop feature that can be flexibly mounted on most of the It is compact in size and it has implemented the geometry of gear teeth.

The device is popular for the quality it offers and lower level of noise emission. The selection of motors and brake motors is large and includes inverter-duty motors. The units are also The CB series of geared motors feature parallel gears and compact modular mounting. Features include a low-speed shaft, a cast iron frame with a monoblocc ribbed design and numerous solutions for The Emerson Compabloc- LSMV is an innovative, decentralized variable speed geared motor made up of a monobloc ribbed cast iron framework ensuring maximum shock and vibration resistance from its environment.

Emerson Industrial Automation presents its latest creation, the Compabloc Varmeca. Is made with compact and space-saving design. Has integrated variable speed that eliminates installation costs, ease of commissioning and promotes flexibility, It also has a decreased weight of the geared motor assembly. This compact modular mounting is a hollow shaft with protective cover or cylindrical output with key or hollow shaft with shrink disk.

It has high efficiency that saves energy. It contains monobloc cast iron frame, ribbed with internal Single - phase asynchronous motor. Quiet operation with a high starting torque. Allows rotation in a defined direction clockwise or counterclockwise.

Its range of Gear Ratios is 1. The size of its The two main types of AC motors are induction motors and synchronous motors. The induction motor or asynchronous motor always relies on a small difference in speed between the stator rotating magnetic field and the rotor shaft speed called slip to induce rotor current in the rotor AC winding.

As a result, the induction motor cannot produce torque near synchronous speed where induction or slip is irrelevant or ceases to exist. In contrast, the synchronous motor does not rely on slip-induction for operation and uses either permanent magnets, salient poles having projecting magnetic poles , or an independently excited rotor winding. The synchronous motor produces its rated torque at exactly synchronous speed. The brushless wound-rotor doubly fed synchronous motor system has an independently excited rotor winding that does not rely on the principles of slip-induction of current.

The brushless wound-rotor doubly fed motor is a synchronous motor that can function exactly at the supply frequency or sub to super multiple of the supply frequency.

Other types of motors include eddy current motors, and AC and DC mechanically commutated machines in which speed is dependent on voltage and winding connection. Alternating current technology was rooted in Michael Faraday 's and Joseph Henry 's —31 discovery that a changing magnetic field can induce an electric current in a circuit. Faraday is usually given credit for this discovery since he published his findings first. In , French instrument maker Hippolyte Pixii generated a crude form of alternating current when he designed and built the first alternator.

It consisted of a revolving horseshoe magnet passing over two wound wire coils. Because of AC's advantages in long distance high voltage transmission, there were many inventors in the United States and Europe during the late 19th century trying to develop workable AC motors.

Ferraris demonstrated a working model of his single-phase induction motor in , and Tesla built his working two-phase induction motor in and demonstrated it at the American Institute of Electrical Engineers in [7] [8] [9] although Tesla claimed that he conceived the rotating magnetic field in If the rotor of a squirrel cage motor were to run at the true synchronous speed, the flux in the rotor at any given place on the rotor would not change, and no current would be created in the squirrel cage.

For this reason, ordinary squirrel-cage motors run at some tens of RPM slower than synchronous speed. Because the rotating field or equivalent pulsating field effectively rotates faster than the rotor, it could be said to slip past the surface of the rotor. The difference between synchronous speed and actual speed is called slip , and loading the motor increases the amount of slip as the motor slows down slightly.

Even with no load, internal mechanical losses prevent the slip from being zero. 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:.

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. 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.

This kind of rotor is the basic hardware for induction regulators , which is an exception of the use of rotating magnetic field as pure electrical not electromechanical application.

Most common AC motors use the squirrel-cage rotor , which will be found in virtually all domestic and light industrial alternating current motors. The squirrel-cage refers to the rotating exercise cage for pet animals. The motor takes its name from the shape of its rotor "windings"- a ring at either end of the rotor, with bars connecting the rings running the length of the rotor. It is typically cast aluminum or copper poured between the iron laminates of the rotor, and usually only the end rings will be visible.

The vast majority of the rotor currents will flow through the bars rather than the higher-resistance and usually varnished laminates. Very low voltages at very high currents are typical in the bars and end rings; high efficiency motors will often use cast copper to reduce the resistance in the rotor. In operation, the squirrel-cage motor may be viewed as a transformer with a rotating secondary. When the rotor is not rotating in sync with the magnetic field, large rotor currents are induced; the large rotor currents magnetize the rotor and interact with the stator's magnetic fields to bring the rotor almost into synchronization with the stator's field.

An unloaded squirrel-cage motor at rated no-load speed will consume electrical power only to maintain rotor speed against friction and resistance losses. As the mechanical load increases, so will the electrical load — the electrical load is inherently related to the mechanical load. This is similar to a transformer, where the primary's electrical load is related to the secondary's electrical load.

This is why a squirrel-cage blower motor may cause household lights to dim upon starting, but does not dim the lights on startup when its fan belt and therefore mechanical load is removed.

Furthermore, a stalled squirrel-cage motor overloaded or with a jammed shaft will consume current limited only by circuit resistance as it attempts to start. Unless something else limits the current or cuts it off completely overheating and destruction of the winding insulation is the likely outcome. Virtually every washing machine , dishwasher , standalone fan , record player , etc. 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 a 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.

With bidirectionally controlled power, the wound rotor becomes an active participant in the energy conversion process, with the wound rotor doubly fed configuration showing twice the power density. 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. Several methods of starting a polyphase motor are used. Where a 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 direct-on-line, DOL.

Where it is necessary to limit the starting inrush current where the motor is large compared with the short-circuit capacity of the supply , the motor is started at reduced voltage using either series inductors, an autotransformer , thyristors , or other devices.

This technique is more common in Europe than in North America. Transistorized drives can directly vary the applied voltage as required by the starting characteristics of the motor and load.

This type of motor is becoming more common in traction applications such as locomotives, where it is known as the asynchronous traction motor [ citation needed ].

A typical two-phase AC servo-motor has a squirrel cage rotor and a field consisting of two windings:. An AC servo amplifier, a linear power amplifier, feeds the control winding. The electrical resistance of the rotor is made high intentionally so that the speed—torque curve is fairly linear. Two-phase servo motors are inherently high-speed, low-torque devices, heavily geared down to drive the load.

Single-phase motors do not have a unique rotating magnetic field like multi-phase motors. The field alternates reverses polarity between pole pairs and can be viewed as two fields rotating in opposite directions.

They require a secondary magnetic field that causes the rotor to move in a specific direction. After starting, the alternating stator field is in relative rotation with the rotor. Several methods are commonly used:. A common single-phase motor is the shaded-pole motor and is used in devices requiring low starting torque , such as electric fans , small pumps, or 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.

This causes a time lag in the flux passing through the shading coil, so that the maximum field intensity moves higher across the pole face on each cycle. This produces a low level rotating magnetic field which is large enough to turn both the rotor and its attached load. As the rotor picks up speed the torque builds up to its full level as the principal magnetic field is rotating relative to the rotating rotor.

A reversible shaded-pole motor was made by Barber-Colman several decades ago. It had a single field coil, and two principal poles, each split halfway to create two pairs of poles. Each of these four "half-poles" carried a coil, and the coils of diagonally opposite half-poles were connected to a pair of terminals. One terminal of each pair was common, so only three terminals were needed in all. The motor would not start with the terminals open; connecting the common to one other made the motor run one way, and connecting common to the other made it run the other way.

These motors were used in industrial and scientific devices. An unusual, adjustable-speed , low-torque shaded-pole motor could be found in traffic-light and advertising-lighting controllers. The pole faces were parallel and relatively close to each other, with the disc centred between them, something like the disc in a watthour meter. Each pole face was split, and had a shading coil on one part; the shading coils were on the parts that faced each other.

Both shading coils were probably closer to the main coil; they could have both been farther away, without affecting the operating principle, just the direction of rotation. Applying AC to the coil created a field that progressed in the gap between the poles. The plane of the stator core was approximately tangential to an imaginary circle on the disc, so the travelling magnetic field dragged the disc and made it rotate.

The stator was mounted on a pivot so it could be positioned for the desired speed and then clamped in position. Keeping in mind that the effective speed of the travelling magnetic field in the gap was constant, placing the poles nearer to the centre of the disc made it run relatively faster, and toward the edge, slower.

Another common single-phase AC motor is the split-phase induction motor , [18] commonly used in major appliances such as air conditioners and clothes dryers. Compared to the shaded pole motor, these motors provide much greater starting torque. A split-phase motor has a secondary startup winding that is 90 electrical degrees to the main winding, always centered directly between the poles of the main winding, and connected to the main winding by a set of electrical contacts.

The coils of this winding are wound with fewer turns of smaller wire than the main winding, so it has a lower inductance and higher resistance. The position of the winding creates a small phase shift between the flux of the main winding and the flux of the starting winding, causing the rotor to rotate.

When the speed of the motor is sufficient to overcome the inertia of the load, the contacts are opened automatically by a centrifugal switch or electric relay.

The direction of rotation is determined by the connection between the main winding and the start circuit. In applications where the motor requires a fixed rotation, one end of the start circuit is permanently connected to the main winding, with the contacts making the connection at the other end.

A capacitor start motor is a split-phase induction motor with a starting capacitor inserted in series with the startup winding, creating an LC circuit which produces a greater phase shift and so, a much greater starting torque than both split-phase and shaded pole motors. A resistance start motor is a split-phase induction motor with a starter inserted in series with the startup winding, creating reactance.

This added starter provides assistance in the starting and initial direction of rotation. Another variation is the permanent-split capacitor or PSC motor. PSC motors are the dominant type of split-phase motor in Europe and much of the world, but in North America, they are most frequently used in variable torque applications like blowers, fans, and pumps and other cases where variable speeds are desired. A capacitor with a relatively low capacitance, and relatively high voltage rating, is connected in series with the start winding and remains in the circuit during the entire run cycle.

There are significant differences, however; the use of a speed sensitive centrifugal switch requires that other split-phase motors must operate at, or very close to, full speed.

PSC motors may operate within a wide range of speeds, much lower than the motor's electrical speed. Also, for applications like automatic door openers that require the motor to reverse rotation often, the use of a mechanism requires that a motor must slow to a near stop before contact with the start winding is re-established. The 'permanent' connection to the capacitor in a PSC motor means that changing rotation is instantaneous.

Three-phase motors can be converted to PSC motors by making common two windings and connecting the third via a capacitor to act as a start winding. 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 synchronously with the rotating magnetic field produced by the polyphase electrical supply.

Another synchronous motor system is the brushless wound-rotor doubly fed synchronous motor system with an independently excited rotor multiphase AC winding set that may experience slip-induction beyond synchronous speeds but like all synchronous motors, does not rely on slip-induction for torque production.

The synchronous motor can also be used as an alternator. Contemporary synchronous motors are frequently driven by solid state 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: Synchronous motors are occasionally used as traction motors ; the TGV may be the best-known example of such use.

Huge numbers of three phase synchronous motors are now fitted to electric cars. They have a Nd or other rare-earth permanent magnet.

One use for this type of motor is its use in a power factor correction scheme. They are referred to as synchronous condensers. This exploits a feature of the machine where it consumes power at a leading power factor when its rotor is over excited. It thus appears to the supply to be a capacitor, and could thus be used to correct the lagging power factor that is usually presented to the electric supply by inductive loads.

The excitation is adjusted until a near unity power factor is obtained often automatically. Machines used for this purpose are easily identified as they have no shaft extensions. Synchronous motors are valued in any case because their power factor is much better than that of induction motors, making them preferred for very high power applications.

Some of the largest AC motors are pumped-storage hydroelectricity generators that are operated as synchronous motors to pump water to a reservoir at a higher elevation for later use to generate electricity using the same machinery.

When pumping, each unit can produce , horsepower Small single-phase AC motors can also be designed with magnetized rotors or several variations on that idea; see "Hysteresis synchronous motors" below.

If a conventional squirrel-cage rotor has flats ground on it to create salient poles and increase reluctance, it will start conventionally, but will run synchronously, although it can provide only a modest torque at synchronous speed.

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