It was a "squirrel cage jail" with three floors of revolving cells inside cages.
|
|
Figure 1. Squirrel cage rotor A squirrel-cage rotor is the rotating part of the common squirrel-cage induction motor. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. In operation, the non-rotating stator winding is connected to an alternating current power source; the alternating current in the stator produces a rotating magnetic field.
|
|
The Pottawattamie County Jail, also known as 'Squirrel Cage Jail' in Council Bluffs, Iowa, United States was built in 1885 and it was listed on the National Register of Historic Places in 1972. The building is a Squirrel Cage Jail, also known as a Rotary Jail.
|
|
A synchronous motor may have a squirrel-cage winding embedded in its rotor, used to increase the motor starting torque and so decrease the time to accelerate to synchronous speed. The squirrel cage winding of a synchronous machine will generally be smaller than for an induction machine of similar rating. When the rotor is turning at the same speed as the stator's revolving magnetic field, no current is induced into the squirrel-cage windings and the windings will have no further effect on the operation of the synchronous motor at steady- state. The squirrel cage winding in some machines provides a damping effect for load or system disturbances, and in this role may be designated as an amortisseur windings.
|
|
Also known as the "Squirrel Cage Jail," it is now a museum and is on the National Register of Historic Places.
|
|
An induction motor can therefore be made without electrical connections to the rotor. An induction motor's rotor can be either wound type or squirrel-cage type. Three-phase squirrel-cage induction motors are widely used as industrial drives because they are self-starting, reliable and economical. Single-phase induction motors are used extensively for smaller loads, such as household appliances like fans.
|
|
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. uses some variant of a squirrel-cage motor.
|
|
Figure 2. Diagram of the squirrel-cage (showing only three laminations) The motor rotor shape is a cylinder mounted on a shaft. Internally it contains longitudinal conductive bars (usually made of aluminium or copper) set into grooves and connected at both ends by shorting rings forming a cage-like shape. The name is derived from the similarity between this rings-and-bars winding and a squirrel cage.
|
|
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.
|
|
Ahern's topper strip, The Squirrel Cage, which ran above Room and Board from June 21, 1936 until at least 1947, is notable because of the repetitive use of the nonsensical question, '"Nov shmoz ka pop?", which was never translated yet became a national catch phrase. As a consequence, The Squirrel Cage and Our Boarding House are today both better remembered than Room and Board, despite its 17-year run.
|
|
Like other modern cars on the Nagoya Subway lines, the 5050 series uses a variable-frequency drive controller to convert DC current to AC current to power a squirrel cage motor.
|
|
Like other modern cars on the Nagoya Subway lines, the 3050 series uses a variable-frequency drive controller to convert DC current to AC current to power a squirrel cage motor.
|
|
The rotary mechanism was disabled as late as 1960, following an incident.Historical Society of Pottawattamie - History of the "Squirrel Cage" Jail The last operating rotary jail in existence is in Crawfordsville, Indiana.
|
|
In so doing, he quickly learned that he was not going to find the solution to the problem by using a normal squirrel-cage rotor. He failed a few times, but his failures finally led to the realization that the performance characteristics he was seeking might be obtained by using permanent magnet steel for the rotor instead of the original squirrel cage induction type rotor. He built many models and finally accomplished the desired operating characteristics. This motor design is covered by Patent No. 1,935,208 and related patents.
|
|
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.
|
|
Council Bluffs is the location of the Pottawattamie County "Squirrel Cage" Jail, in use from 1885 until 1969, which is one of three remaining examples of a Rotary Jail. Listed on the National Register of Historic Places, it was built as a rotary jail with pie-shaped cells on a turntable. To access individual cells, the jailer turned a crank to rotate the cylinder until the desired cell lined up with a fixed opening on each floor. According to the Historical Society of Pottawattamie County, the Squirrel Cage Jail is the only three-story rotary jail constructed.
|
|
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.
|
|
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, aside from stabilizing the motor speed on load changes. 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.
|
|
A centrifugal mechanism, when close to running speed, connected all commutator bars together to create the equivalent of a squirrel-cage rotor. As well, when close to approximately 80 per cent of its run speed, these motors can run as induction motors.
|
|
In the latter case, all commutator segments are connected together as well, before the motor attains running speed. Once at speed, the rotor windings become functionally equivalent to the squirrel-cage structure of a conventional induction motor, and the motor runs as such.
|
|
Schematic of a capacitor start motor. The motor which drives the fan and the oil pump is usually a capacitor start motor. It is a single phase, squirrel cage induction motor. The difference with a three-phase motor is in the stator.
|
|
The effect is more pronounced in doubly-fed induction generators (DFIG), which have two sets of powered magnetic windings, than in squirrel-cage induction generators which have only one. Synchronous generators may slip and become unstable, if the voltage of the stator winding goes below a certain threshold.
|
|
These were used where high starting torque was required. They started as repulsion motors, but once they were running at a sizable fraction of full speed, the brushes were lifted mechanically and all commutator bars were short-circuited together to create the equivalent of a squirrel-cage induction motor.
|
|
Hot coolant passing through the heater core gives off heat before returning to the engine cooling circuit. The squirrel cage fan of the vehicle's ventilation system forces air through the heater core to transfer heat from the coolant to the cabin air, which is directed into the vehicle through vents at various points.
|
|
The term premium efficiency as discussed here relates to a class of motor efficiency. It is thought necessary to introduce this term associated with motors because of forthcoming legislation in the EU, USA and other countries regarding the future mandatory use of premium-efficiency squirrel cage induction type motors in defined equipment.
|
|
Schematic symbol of a slip ring motor A wound-rotor motor, also known as slip ring-rotor motor, is a type of induction motor where the rotor windings are connected through slip rings to external resistance. Adjusting the resistance allows control of the speed/torque characteristic of the motor. Wound-rotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit; as the motor accelerates, the resistance can be decreased.Harold J. Herbein Rotating Machinery, Rinehart Press, 1971, SBN 03-084675-7, pages 215-218 Compared to a squirrel-cage rotor, the rotor of the slip ring motor has more winding turns; the induced voltage is then higher, and the current lower, than for a squirrel-cage rotor.
|
|
As a result the inrush current is reduced. Another important advantage over squirrel-cage motors is higher starting torque. The construction of slip ring induction motor is quite different compared to other induction motor. Slip rings Induction motor provides some advantages like provides high starting torque, low starting current and it improves the power factor.
|
|
A typical two-phase AC servo-motor has a squirrel cage rotor and a field consisting of two windings: # a constant-voltage (AC) main winding. # a control-voltage (AC) winding in quadrature (i.e., 90 degrees phase shifted) with the main winding so as to produce a rotating magnetic field. Reversing phase makes the motor reverse.
|
|
It's gone full circle. People now state their hostility, or if they're much too busy being caught up in the squirrel cage, they let the Box Cards state their hostility for them. This is not to say that I think the work of Bill Box is merely a statement of hostility or anything sick.Box, Bill and Bill Kennedy.
|
|
Very small reluctance motors have low torque, and are generally used for instrumentation applications. Moderate torque, multi-horsepower motors use squirrel cage construction with toothed rotors. When used with an adjustable frequency power supply, all motors in the drive system can be controlled at exactly the same speed. The power supply frequency determines motor operating speed.
|
|
Transformers and Motors, by George Patrick Shultz By way of contrast, AC synchronous and squirrel cage induction motors cannot turn a shaft faster than allowed by the power line frequency. In countries with 60Hz AC supply, this speed is limited to 3600RPM.Herman, Stephen L. Delmar's Standard Textbook of Electricity, 3rd Edition. Clifton Park, NY: Delmar Learning, 2004. p.
|
|
Some elements of the plot bear a similarity to that of The Squirrel Cage, a short story by Thomas M. Disch first published in 1966 in New Worlds magazine. Both stories are about a man who is imprisoned in a white cube, has no memory of a time before, and never discovers the purpose of his entrapment. The similarities end there as the man in The Squirrel Cage is never visited by others as is the man in The Cube. He instead makes up stories, and regularly reads a newspaper that is provided for him daily. At one point Henson comments on his own teleplay through a Professor who wanders in from yet another door: :PROFESSOR: Well, as I interpret what you’re doing here, this is all a very complex discussion of reality versus Illusion.
|
|
These motors have a stator like those of capacitor-run squirrel-cage induction motors. On startup, when slip decreases sufficiently, the rotor becomes magnetized by the stator's field, and the poles stay in place. The motor then runs at synchronous speed as if the rotor were a permanent magnet. When stopped and restarted, the poles are likely to form at different locations.
|
|
Although traditionally used in fixed-speed service, induction motors are increasingly being used with variable-frequency drives (VFD) in variable-speed service. VFDs offer especially important energy savings opportunities for existing and prospective induction motors in variable-torque centrifugal fan, pump and compressor load applications. Squirrel-cage induction motors are very widely used in both fixed-speed and variable-frequency drive applications.
|
|
The General Electric Company began developing three-phase induction motors in 1891. By 1896, General Electric and Westinghouse signed a cross-licensing agreement for the bar-winding-rotor design, later called the squirrel-cage rotor. Induction motor improvements flowing from these inventions and innovations were such that a 100-horsepower induction motor currently has the same mounting dimensions as a 7.5-horsepower motor in 1897.
|
|
Although the efficiency is not high, this fan is well suited for applications with extremely high dust loading. It can be offered with field-replaceable blade liners from ceramic tiles or tungsten carbide. This fan may also be used in high-temperature applications. Forward- curve – This "squirrel cage" impeller generates the highest volume flow rate (for a given tip speed) of all the centrifugal fans.
|
|
No matter whether it appeared above or below a main strip, the extra strip was known as the topper, such as The Squirrel Cage which ran along with Room and Board, both drawn by Gene Ahern. During the 1930s, the original art for a Sunday strip was usually drawn quite large. For example, in 1930, Russ Westover drew his Tillie the Toiler Sunday page at a size of 17" × 37".
|
|
Boucherot was interested in using polyphase supplies to power asynchronous motors as early as 1894. The squirrel-cage rotor asynchronous motor was invented by Mikhail Dolivo-Dobrovolsky in 1889 and they were being built industrially from 1891. A problem with asynchronous machines is that they are difficult to start. The coupling to the rotor is weak until it gets moving and the current drawn by the motor is high.
|
|
As the motor accelerates, the slip frequency decreases and induced current flows at greater depths in the winding. By tapering the profile of the rotor bars to vary their resistance at different depths, or by constructing a double squirrel cage, with a combination of high and low impedance rotor in parallel the motor can be arranged to produce more or less torque at standstill and near its synchronous speed.
|
|
Thus at synchronous speed the rotor is "locked" to the rotating stator field. This cannot start the motor, so the rotor poles usually have squirrel-cage windings embedded in them, to provide torque below synchronous speed. The machine starts as an induction motor until it approaches synchronous speed, when the rotor "pulls in" and locks to the rotating stator field. Reluctance motor designs have ratings that range from fractional horsepower (a few watts) to about .
|
|
A water-cooled OHC four-cylinder engine, producing , was mounted in back, hence the "H", from German heck (rear). The radiator was behind that, above the transaxle, with a squirrel-cage blower (reminiscent of the VW Type 1) feeding both radiator and carburetor. The roadster featured disc wheels, DuVal-style windshield, side-mounted spare (fastened with straps), and three headlights, the third mounted at the lip of the hood above the bumper.Lyons, p.
|
|
Self-starting polyphase induction motors produce torque even at standstill. Available squirrel-cage induction motor starting methods include direct-on-line starting, reduced-voltage reactor or auto-transformer starting, star-delta starting or, increasingly, new solid-state soft assemblies and, of course, variable frequency drives (VFDs). Polyphase motors have rotor bars shaped to give different speed-torque characteristics. The current distribution within the rotor bars varies depending on the frequency of the induced current.
|
|
An induction motor is an asynchronous AC motor where power is transferred to the rotor by electromagnetic induction, much like transformer action. An induction motor resembles a rotating transformer, because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the secondary side. Polyphase induction motors are widely used in industry. Induction motors may be further divided into Squirrel Cage Induction Motors and Wound Rotor Induction Motors (WRIMs).
|
|
Slip rings and brushes are used to conduct current to the rotor. The rotor poles connect to each other and move at the same speed hence the name synchronous motor. Another type, for low load torque, has flats ground onto a conventional squirrel-cage rotor to create discrete poles. Yet another, such as made by Hammond for its pre-World War II clocks, and in the older Hammond organs, has no rotor windings and discrete poles.
|
|
Three phase squirrel cage induction motors can also be used as generators. For this to work the motor must see a reactive load, and either be connected to a grid supply or an arrangement of capacitors to provide excitation current. For the motor to work as a generator instead of a motor the rotor must be spun faster than its stator's synchronous speed. This will cause the motor to generate power after building up its residual magnetism.
|
|
This was a reprise of a move King had made nine years earlier, hiring George Swanson (Elza Poppin) to produce a duplicate of his own NEA strip, Salesman Sam, and it had a similar result — success, but not to the extent of the original. When, in 1953, Ahern retired, Room and Board ended. Today, its memory is overshadowed by its own topper, The Squirrel Cage, where the enigmatically familiar phrase, "Nov shmoz ka pop?" was introduced.Our Boarding House at Don Markstein's Toonopedia.
|
|
In 1936 a centrifugal fan, brake motors and small induction motors program from another manufacturer named HSM (short for: Heinke-Schuitema- Musselkanaal) in Musselkanaal was bought and brought to Rotterdam. Mr. K.W. Heinke, one of the former owners and mechanical engineer of HSM also moved to work at the factory in Rotterdam. In the same year 40 off. patents were applied for, with reference to three inventions: the centrifugal switch, the centrifugal fan housing and the principle of a squirrel-cage rotor.
|
|
Dolivo- Dobrowolsky worked with chained three-phase alternating current and introduced the term three-phase current. The associated asynchronous motor invented by him was the first functional solution. However, the asynchronous motor with squirrel-cage rotor had the problem of delivering only low torque at low speeds, such as when starting up. The solution was the slip ring motor, a variation of the asynchronous motor in which the short circuit of the rotor is opened and guided to the outside via sliprings.
|
|
Industrial Electronics, IEEE Transactions on. 1996\. However, some incorporate a squirrel cage in the rotor for starting — these are known as line-start or self-starting PMSMs. These are typically used as higher-efficiency replacements for induction motors (owing to the lack of slip), but need to be specified carefully for the application to ensure that synchronous speed is reached and that the system can withstand the torque ripple during starting. Permanent magnet synchronous motors are mainly controlled using direct torque control and field oriented control.
|
|
Above a certain size, synchronous motors are not self- starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator. Since a synchronous motor produces no inherent average torque at standstill, it cannot accelerate to synchronous speed without some supplemental mechanism. Large motors operating on commercial power frequency include a squirrel-cage induction winding which provides sufficient torque for acceleration and which also serves to damp oscillations in motor speed in operation.
|
|
At low speeds, the current induced in the squirrel cage is nearly at line frequency and tends to be in the outer parts of the rotor cage. As the motor accelerates, the slip frequency becomes lower, and more current is in the interior of the winding. By shaping the bars to change the resistance of the winding portions in the interior and outer parts of the cage, effectively a variable resistance is inserted in the rotor circuit. However, the majority of such motors have uniform bars.
|
|
Construction of the jail was simultaneous with that of the county's new courthouse, which was finished in 1888. It was designed by William H. Brown and Benjamin F. Haugh of Indianapolis, Indiana at a cost of $30,000. The building was one of 18 such jails that were built in the United States and the only one that was three stories tall. Also known as 'Squirrel Cage Jail', it was one of a handful of rotary jails built in the Midwestern America in the mid-19th century.
|
|
In single phase squirrel cage motors, the primary winding within the motor housing is not capable of starting a rotational motion on the rotor, but is capable of sustaining one. To start the motor, a secondary "start" winding has a series non-polarized starting capacitor to introduce a lead in the sinusoidal current. When the secondary (start) winding is placed at an angle with respect to the primary (run) winding, a rotating electric field is created. The force of the rotational field is not constant, but is sufficient to start the rotor spinning.
|
|
A major advantage of the hysteresis motor is that since the lag angle δ is independent of speed, it develops constant torque from startup to synchronous speed. Therefore, it is self-starting and doesn't need an induction winding to start it, although many designs do have a squirrel-cage conductive winding structure embedded in the rotor to provide extra torque at start-up. Hysteresis motors are manufactured in sub-fractional horsepower ratings, primarily as servomotors and timing motors. More expensive than the reluctance type, hysteresis motors are used where precise constant speed is required.
|
|
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.
|
|
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. This is known as a reluctance 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.
|
|
Air handlers typically employ a large squirrel cage blower driven by an AC induction electric motor to move the air. The blower may operate at a single speed, offer a variety of set speeds, or be driven by a variable-frequency drive to allow a wide range of air flow rates. Flow rate may also be controlled by inlet vanes or outlet dampers on the fan. Some residential air handlers in USA (central "furnaces" or "air conditioners") use a brushless DC electric motor that has variable speed capabilities.
|
|
It also allows designs which make it very easy to manufacture the rotor. A metal cylinder will work as rotor, but to improve efficiency a "squirrel cage" rotor or a rotor with closed windings is usually used. The speed of asynchronous induction machines will decrease with increased load because a larger speed difference between stator and rotor is necessary to set up sufficient rotor current and rotor magnetic field. Asynchronous induction machines can be made so they start and run without any means of control if connected to an AC grid, but the starting torque is low.
|
|
Lycoming O-320 mounted in a Robinson R22 Beta The R22 is a simple and tight design The R22 uses a horizontally mounted Lycoming O-320 (O-360-J2A on the Beta II), flat-four, air-cooled, normally aspirated, carburetor-equipped reciprocating engine. It is fueled with 100LL grade aviation gasoline. Cooling is provided through a direct drive squirrel-cage cooling fan. At sea level it is derated, or operated at less than maximum power, which has been attributed to the company wishing for the power unit to maintain the same performance at sea level as it does at altitude.
|
|
For example, a utility may require rural customers to use reduced-voltage starters for motors larger than 10 kW.Terrell Croft and Wilford Summers (ed), American Electricans' Handbook, Eleventh Edition, McGraw Hill, New York (1987) pages 78-150 through 7-159 DOL starting is sometimes used to start small water pumps, compressors, fans and conveyor belts. In the case of an asynchronous motor, such as the 3-phase squirrel-cage motor, the motor will draw a high starting current until it has run up to full speed. This starting current is typically 6-7 times greater than the full load current.
|
|
A PCI Express 3.0 ×16 graphics card, using two fans for cooling Used to cool the heatsink of the graphics processing unit or the memory on graphics cards. These fans were not necessary on older cards because of their low power dissipation, but most modern graphics cards designed for 3D graphics and gaming need their own dedicated cooling fans. Some of the higher powered cards can produce more heat than the CPU (dissipating up to 289 watts), so effective cooling is especially important. Since 2010, graphics cards have been released with either axial fans, or a centrifugal fan also known as a blower, turbo or squirrel cage fan.
|
|
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.
|
|
The rotor winding has current induced in it by the stator field, like a transformer except that the current in the rotor is varying at the stator field rotation rate minus the physical rotation rate. The interaction of the magnetic fields of currents in the stator and rotor produce a torque on the rotor. By adjusting the shape of the bars in the rotor, the speed-torque characteristics of the motor can be changed, to minimize starting current or to maximize low-speed torque, for example. Squirrel-cage induction motors are very prevalent in industry, in sizes from below up to tens of megawatts (tens-of-thousand horsepower).
|
|
A typical motor start capacitor, as can be seen by its black color and can shape In single phase squirrel cage motors, the primary winding within the motor housing is not capable of starting a rotational motion on the rotor, but is capable of sustaining one. To start the motor, a secondary winding is used in series with a non-polarized starting capacitor to introduce a lag in the sinusoidal current through the starting winding. When the secondary winding is placed at an angle with respect to the primary winding, a rotating electric field is created. The force of the rotational field is not constant, but is sufficient to start the rotor spinning.
|
|
A 3D illustration of six 80 mm fans, a type of fan commonly used in personal computers (sometimes as a set, or mixed with other fan sizes) A PC fan laying atop one sized A computer fan is any fan inside, or attached to, a computer case used for active cooling. Fans are used to draw cooler air into the case from the outside, expel warm air from inside and move air across a heat sink to cool a particular component. Both axial and sometimes centrifugal (blower/squirrel-cage) fans are used in computers. Computer fans commonly come in standard sizes, and are powered and controlled using 3-pin or 4-pin fan connectors.
|
|
Gene Ahern's The Squirrel Cage (January 3, 1937), an example of a topper strip which is better remembered than the strip it accompanied, Ahern's Room and Board. Russell Patterson and Carolyn Wells' New Adventures of Flossy Frills (January 26, 1941), an example of comic strips on Sunday magazines. Sunday newspapers traditionally included a special color section. Early Sunday strips (known colloquially as "the funny papers", shortened to "the funnies"), such as Thimble Theatre and Little Orphan Annie, filled an entire newspaper page, a format known to collectors as full page. Sunday pages during the 1930s and into the 1940s often carried a secondary strip by the same artist as the main strip.
|
|
Westinghouse achieved its first practical induction motor in 1892 and developed a line of polyphase 60 hertz induction motors in 1893, but these early Westinghouse motors were two-phase motors with wound rotors. B.G. Lamme later developed a rotating bar winding rotor. Steadfast in his promotion of three-phase development, Mikhail Dolivo- Dobrovolsky invented the three-phase induction motor in 1889, of both types cage-rotor and wound rotor with a starting rheostat, and the three-limb transformer in 1890. After an agreement between AEG and Maschinenfabrik Oerlikon, Doliwo-Dobrowolski and Charles Eugene Lancelot Brown developed larger models, namely a 20-hp squirrel cage and a 100-hp wound rotor with a starting rheostat.
|
|
Some include a squirrel-cage structure to bring the rotor close to synchronous speed. Various other 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 the latter instance, applying AC power creates chaotic (or seemingly chaotic) jumping movement back and forth; such a motor will always start, but lacking the anti-reversal mechanism, the direction it runs is unpredictable. The Hammond organ tone generator used a non-self-starting synchronous motor (until comparatively recently), and had an auxiliary conventional shaded-pole starting motor.
|
|
Pumps come in diameters from 90mm (3.5 inches) to 254mm (10 inches) and vary between and in length. The motor used to drive the pump is typically a three phase, squirrel cage induction motor, with a nameplate power rating in the range 7.5 kW to 560 kW (at 60 Hz). ESP assemblies may also include: seals coupled to the shaft between the motor and pump; screens to reject sand; and fluid separators at the pump intake that separate gas, oil and water. ESPs have dramatically lower efficiencies with significant fractions of gas, greater than about 10% volume at the pump intake, so separating gas from oil prior to the pump can be important.
|
|
Mikhail Osipovich Dolivo-Dobrovolsky Mikhail Osipovich Dolivo-Dobrovolsky (; or Michail Ossipowitsch Doliwo-Dobrowolski; ; - ) was a Polish-Russian engineer, electrician, and inventor. As one of the founders (the others were Nikola Tesla, Galileo Ferraris and Jonas Wenström) of polyphase electrical systems, he developed the three-phase electrical generator and a three-phase electrical motor (1888) and studied star and delta connections. The triumph of the three-phase system was displayed in Europe at the International Electro- Technical Exhibition of 1891, where Dolivo-Dobrovolsky used this system to transmit electric power at the distance of 176 km with 75% efficiency. In 1891 he also created a three-phase transformer and short-circuited (squirrel-cage) induction motor.
|
|
Although Westinghouse achieved its first practical induction motor in 1892 and developed a line of polyphase 60 hertz induction motors in 1893, these early Westinghouse motors were two-phase motors with wound rotors until B. G. Lamme developed a rotating bar winding rotor. The General Electric Company (GE) began developing three-phase induction motors in 1891. By 1896, General Electric and Westinghouse signed a cross-licensing agreement for the bar-winding-rotor design, later called the squirrel-cage rotor. Arthur E. Kennelly was the first to bring out the full significance of complex numbers (using j to represent the square root of minus one) to designate the 90º rotation operator in analysis of AC problems.
|
|
As it was deprived of its driving turbine, the alternator was run up to speed by using its rotor damping winding as a squirrel cage, the stator being fed from another turbo running at reduced speed and voltage. When the rotor had come up to speed, excitation was applied to achieve synchronism. Originally equipped with reciprocating steam engines, during its long life a total of eighteen generating sets were installed and in turn replaced with larger units or scrapped. The final equipment was of fairly typical 1940's design with eight Babcock stoker-fired boilers using the range system, feeding two British Thomson-Houston 34 MW sets and two Richardsons-Westgarth 30 MW sets, running at 650 psi and superheat.
|
|
In effect the rotor is carried around with the magnetic field but at a slightly slower rate of rotation. The difference in speed is called slip and increases with load. The conductors are often skewed slightly along the length of the rotor to reduce noise and smooth out torque fluctuations that might result at some speeds due to interactions with the pole pieces of the stator, by ensuring that at any time the same fraction of a rotor bar is under each stator slot. (if this is not done the motor will experience a drop and then recovery in torque as each bar passes the gap in the stator) The number of bars on the squirrel cage determines to what extent the induced currents are fed back to the stator coils and hence the current through them.
|
|
The concept of a flywheel-powered bus was developed and brought to fruition during the 1940s by Oerlikon (of Switzerland), with the intention of creating an alternative to trolleybuses for quieter, lower- frequency routes, where full overhead-wire electrification could not be justified. Loading up the flywheel with three-phase charging Rather than carrying an internal combustion engine or batteries, or connecting to overhead powerlines, a gyrobus carries a large flywheel that is spun at up to 3,000 RPM by a "squirrel cage" motor. Power for charging the flywheel was sourced by means of three booms mounted on the vehicle's roof, which contacted charging points located as required or where appropriate (at passenger stops en route, or at terminals, for instance). To obtain tractive power, capacitors would excite the flywheel's charging motor so that it became a generator, in this way transforming the energy stored in the flywheel back into electricity.
|
|
Tesla Museum in Belgrade, Serbia Squirrel-cage rotor construction, showing only the center three laminations In 1824, the French physicist François Arago formulated the existence of rotating magnetic fields, termed Arago's rotations. By manually turning switches on and off, Walter Baily demonstrated this in 1879, effectively the first primitive induction motor.The Electrical engineer, Volume 5. (February, 1890)The Electrician, Volume 50. 1923Official gazette of the United States Patent Office: Volume 50. (1890) The first commutator-free single-phase AC induction motor was invented by Hungarian engineer Ottó Bláthy; he used the single phase motor to propel his invention, the electricity meter. The first AC commutator-free three-phase induction motors were independently invented by Galileo Ferraris and Nikola Tesla, a working motor model having been demonstrated by the former in 1885 and by the latter in 1887. Tesla applied for US patents in October and November 1887 and was granted some of these patents in May 1888.
|
|