Difference between servo motor and induction motor pdf

Please forward this error screen to 69. An industrial type difference between servo motor and induction motor pdf AC motor with electrical terminal box at the top and output rotating shaft on the left. Such motors are widely used for pumps, blowers, conveyors and other industrial machinery. The rotor magnetic field may be produced by permanent magnets, reluctance saliency, or DC or AC electrical windings.

The two main types of AC motors are induction motors and synchronous motors. The synchronous motor produces its rated torque at exactly synchronous speed. AC and DC mechanically commutated machines in which speed is dependent on voltage and winding connection. Faraday is usually given credit for this discovery since he published his findings first.

It consisted of a revolving horseshoe magnet passing over two wound wire coils. United States and Europe during the late 19th century trying to develop workable AC motors. June 28, 1879, to the Physical Society of London. 1880 that identified the rotating magnetic field principle and that of a two-phase AC system of currents to produce it.

In 1887, American inventor Charles Schenk Bradley was the first to patent a two-phase AC power transmission with four wires. Tesla, in the same year, was granted a United States patent for his own motor. 1890, a much more capable design that became the prototype used in Europe and the U. He also invented the first three-phase generator and transformer and combined them into the first complete AC three-phase system in 1891. 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. Even with no load, internal mechanical losses prevent the slip from being zero. With no load, the speed will be very close to synchronous.

Rotational speed, in revolutions per minute. Normalised Slip, 0 to 1. 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 RPM. 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. 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. 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.

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. 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. Several methods of starting a polyphase motor are used. 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. Reversing phase makes the motor reverse. An AC servo amplifier, a linear power amplifier, feeds the control winding. 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. 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.

In this motor, small single-turn copper “shading coils” create the moving magnetic field. 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.

Facebook Comments