An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. 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. Ps3 save data download.

Squirrel cage rotor A squirrel-cage rotor is the rotating part of the common squirrel-cage. 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 power source; the alternating current in the stator produces a. The rotor winding has current induced in it by the stator field, and produces its own magnetic field.

The interaction of the two magnetic fields from these two sources produces 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 one kilowatt (fractional horsepower; less than 1 hp) up to tens of megawatts (10,000s of horsepower). They are simple, rugged, and self-starting, and maintain a reasonably constant speed from light load to full load, set by the frequency of the power supply and the number of poles of the stator winding. Commonly used motors in industry are usually IEC or standard frame sizes, which are interchangeable between manufacturers. This simplifies application and replacement of these motors. Contents • • • • • • • • History [ ] described an induction machine with a two-phase stator winding and a solid copper cylindrical armature in 1885.

In 1888, received a patent on a two-phase induction motor with a short-circuited copper rotor winding and a two-phase stator winding. Developments of this design became commercially important.

In 1889, developed a wound-rotor induction motor, and shortly afterward the cage-type rotor winding. By the end of the 19th century induction motors were widely applied on the growing alternating-current electrical distributions systems. Structure [ ].

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. The solid core of the rotor is built with stacks of electrical steel laminations. Figure 3 shows one of many laminations used.

The rotor has a larger number of slots than the and must be a non-integer multiple of stator slots so as to prevent magnetic interlocking of rotor and stator teeth at the starting instant. The rotor bars may be made of either copper or aluminium. A very common structure uses aluminium poured into the rotor after the laminations are stacked. Some larger motors have aluminium or copper bars which are welded or brazed to end-rings. Since the voltage developed in the squirrel cage winding is very low, no intentional insulation layer is present between the bars and the rotor steel. Stator and rotor laminations The field windings in the stator of an induction motor set up a through the. The relative motion between this field and the rotor induces in the conductive bars.

In turn these currents lengthwise in the conductors react with the magnetic field of the motor to produce acting at a to the rotor, resulting in to turn the shaft. 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. 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.