The speed of an AC motor is dependent on the number of poles it has and the line frequency of the power supply, not on it's voltage. Common AC motor units are constructed with either two or four poles.
The speed of an induction motor is determined by the frequency of the electrical current flowing through the stator's coils and the strength of the stator's magnetic field. In general, higher frequencies and stronger magnetic fields result in faster rotor speeds, while lower frequencies and weaker magnetic fields result in slower rotor speeds.
To understand how the frequency and strength of the stator's magnetic field affect the speed of an induction motor, it is helpful to consider the basic operating principle of this type of motor. An induction motor uses electromagnetic induction to convert electrical energy into mechanical energy. This is accomplished by creating a magnetic field around a coil of wire, which can then be used to generate rotational motion.
In an induction motor, the magnetic field is produced by a stator, which is a stationary component that consists of a series of copper or aluminum coils. The stator is typically mounted on the outer shell of the motor, and it is connected to the electrical power supply. When an electrical current flows through the stator coils, it creates a magnetic field that extends into the rotor, which is a moving component that is mounted on the motor's shaft.
The rotor is typically made up of a series of conductive bars that are connected to a series of short-circuited end rings. When the rotor is placed in the magnetic field produced by the stator, it experiences a force known as the "rotor reaction," which causes it to rotate. This rotational motion is transferred to the motor's shaft, which can then be used to drive a load.
The key to the operation of an induction motor is the interaction between the magnetic fields of the stator and rotor. When the stator's magnetic field rotates, it creates a current in the rotor's conductive bars, which in turn creates its own magnetic field. This magnetic field interacts with the stator's magnetic field, resulting in a force that causes the rotor to rotate.
The speed at which the rotor rotates depends on the frequency of the current flowing through the stator's coils. Higher frequencies result in faster rotor speeds, while lower frequencies result in slower rotor speeds. This is because the frequency of the current determines the rate at which the stator's magnetic field rotates, and the faster the field rotates, the faster the rotor will rotate in response.
In addition to the frequency of the current, the strength of the stator's magnetic field also plays a role in determining the speed of the rotor. A stronger magnetic field will result in a faster rotor speed, as the stronger field will produce a greater force on the rotor, causing it to rotate more quickly.
The speed of an induction motor can also be affected by other factors, such as the load on the motor and the efficiency of the motor itself. In general, heavier loads will cause the rotor to rotate more slowly, as the rotor will have to work harder to overcome the resistance of the load. In addition, motors with lower efficiency levels will tend to have slower rotor speeds, as some of the electrical energy input to the motor will be lost as heat rather than being converted into mechanical energy.
Overall, the speed of an induction motor is determined by the frequency and strength of the stator's magnetic field, as well as by other factors such as the load on the motor and its efficiency. By carefully controlling these factors, it is possible to achieve precise control over the speed of an induction motor, allowing it to be used effectively in a wide range of applications.