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Once AC Induction Motor is up to speed, it operates at a low slip, at a speed determined by the number of the stator poles. Typically, the full-load slip for the squirrel cage ac induction motor is less than 5%. The actual full-load slip of a particular motor is dependant on the motor design. The typical base speed of the four pole induction motor varies between 1420 and 1480 RPM at 50 Hz, while the synchronous speed is 1500 RPM at 50 Hz.

The current, drawn by the ac induction motor, has two components: reactive component (magnetizing current),  active component (working current).

The magnetizing current (reactive component) is independent of the load but is dependant on the design of the stator and the stator voltage. The actual magnetizing current of the induction motor can vary, from as low as 20% of Locked Rotor Current (LRC) for the large two pole machine, to as high as 60% for the small eight pole machine.

The working current (active component) of the motor is directly proportional to the load.

AC induction motors, at rest, appear just like a short circuited transformer and if connected to the full supply voltage, draw a very high current, known as the "Locked Rotor Current (LRC)." They also produce torque which is known as the "Locked Rotor Torque (LRT)". The Locked Rotor Torque (LRT) and the Locked Rotor Current (LRC) are a function of the terminal voltage of the motor and the motor design. As the motor accelerates, both the torque and the current will tend to alter with rotor speed if the voltage is maintained constant.

The starting current of a motor with a fixed voltage will drop very slowly as the motor accelerates, and will only begin to fall significantly when the motor has reached at least 80% of the full speed. The actual curves for ac induction motors can vary considerably between designs. But the general trend is for a high current until the motor has almost reached full speed. The Locked Rotor Current (LRC) of a motor can range from 500% of Full-Load Current (FLC) to as high as 1400% of FLC. Typically, good motors fall in the range of 550% to 750% of Full-Load Current (FLC).

The slip-ring motor (or wound-rotor motor) is a variation of the squirrel cage ac induction motor. While the stator is the same as that of the squirrel cage ac induction motor, it has a set of windings on the rotor which are not short-circuited, but are terminated to a set of slip rings. They are helpful in adding external resistors and contactors.

The slip necessary to generate the maximum torque (pull-out torque) is directly proportional to the rotor resistance. In this slip-ring motor, the effective rotor resistance is increased by adding external resistance through the slip rings. Thus it is possible to get higher slip and hence, the pull-out torque at a lower speed.

A particularly high resistance can result in the pull-out torque occurring at almost zero speed, providing a very high pull-out torque at a low starting current. As the motor accelerates, the value of the resistance can be reduced, altering the motor characteristic to suit the load requirement. Once the 3-phase induction motor reaches the base speed, external resistors are removed from the rotor. This means that now the motor is working as the standard induction motor.

Almost 90% of the three-phase (3 phase)  AC Induction motors are of this type. Of this type of ac motor, the rotor is of the squirrel cage type and it works as explained in this article Three Phase AC Induction Motor.

The power ratings range from one-third to several hundred horsepower (hp) in the three-phase (3 phase) ac induction motors. Squirrel Cage Motor, rated one horsepower (hp) or larger, cost less and can start heavier loads than the single-phase ac induction motor.

Three-phase AC induction motors are widely used in industrial and commercial applications. They are classified as squirrel cage motors and wound-rotor motors.

They produce medium to high degrees of starting torque. The power capabilities and efficiency in these ac motors range from medium to high, compared to the single-phase ac induction motors. Popular applications of three phase induction motors include grinders, lathes, drill presses, pumps, compressors, conveyors, also printing equipment, farm equipment, electronic cooling and other mechanical duty applications.

Depending on the various start techniques, Single-Phase AC Induction Motor is classified: Split-Phase AC Induction Motor, Capacitor Start AC Induction Motor, Permanent Split Capacitor (Capacitor Run) AC Induction Motor, Capacitor Start/Capacitor Run AC Induction Motor, Shaded-Pole AC Induction Motor.

Below is the figure showing the torque-speed curves of various kinds of single-phase AC induction motors.

The rotor of AC induction motor is made up of several thin steel laminations with evenly spaced bars, which are made up of aluminum or copper, along the periphery. And in the most popular type of rotor (squirrel cage rotor), the bars are connected at ends mechanically and electrically by the use of rings. Almost 90% of ac induction motors have squirrel cage rotors. This is because the squirrel cage rotor has a simple and rugged construction. The rotor of ac motor consists of a cylindrical laminated core with axially placed parallel slots for carrying the conductors. Each slot carries a copper, aluminum, or alloy bar. These rotor bars are permanently short-circuited at both ends by means of the end rings, which is shown below. This total assembly resembles the look of a squirrel cage, which gives the rotor its name. The rotor slots are not exactly parallel to the shaft. Instead, they are given a skew for two main reasons.

The first reason: to make the motor run quietly by reducing magnetic hum and to decrease slot harmonics.

The second reason: to help reduce the locking tendency of the rotor of the motor. The rotor teeth tend to remain locked under the stator teeth due to direct magnetic attraction between the two. This happens when the number of stator teeth are equal to the number of rotor teeth.

The stator is the ingredient of AC Motor. The stator of AC Induction Motor is made up of several thin laminations of aluminum or cast iron.

They are punched and clamped together to form a hollow cylinder (stator core) with slots. This is shown in the figure below. Coils of insulated wires are inserted into the slots. Each grouping of coils, together with the core it surrounds, forms an electromagnet (a pair of poles) on the application of AC supply. The number of poles of an AC induction motor depends on the internal connection of the stator windings.

Like most motors in today's industry, an AC induction motor has a fixed outer portion: the stator and a rotor that spins inside with a carefully engineered air gap between the two.

Virtually all electrical motors use magnetic field rotation to spin their rotors.

And a three-phase AC induction motor is the only type, where the rotating magnetic field is created naturally in the stator because of the nature of the supply.

DC motor depends either on mechanical or electronic commutation to create the rotating magnetic fields.

A single-phase AC induction motor depends on the extra electrical components to produce this rotating magnetic field.

Shaded-pole ac induction motors have only one main winding and no start winding. Starting is by means of a design that rings a continuous copper loop around a small portion of each of the ac motor poles. This "shades" that portion of the pole, causing the magnetic field in the shaded area to lag behind the field in the unshaded area. And the reaction of the two fields gets the shaft rotating.

Because the shaded-pole motor lacks a start winding, starting switch or capacitor, this Shaded-Pole AC Induction Motor is electrically simple and inexpensive. Also, the speed of this ac induction motor can be controlled merely by varying voltage, or through a multi-tap winding. Mechanically, the shaded-pole induction motor construction allows high-volume production. In fact, these are usually considered as "disposable" motors, which means they are much cheaper to replace than to repair.