AC Motors

Among the motor options, the AC motor is an electric based on power motor, driven by alternating current, AC, as its power source. Generally, an AC motor is usually composed of two basic components, one is an outside stator, the coil of the outside stator provides AC power to generate a rotating magnetic field, and another is an inside rotor connected to the output shaft, which generates a second rotating magnetic field.
Regarding the rotor magnetic field, depending on the supplier's design and usage considerations, it may be generated by permanent magnets, reluctance salient poles or DC or AC windings. The AC motor is a very common type of motor today, which has been used and adopted in various industrial and domestic fields. It provides a variety of power supply methods for the connected loading units. However, AC linear motors are not very common. They operate on a similar principle, but they have fixed and moving parts and arranged in a linear configuration.

AC Motor Operation Mechanism

There are two main types of AC motors in the market, namely induction motors and synchronous motors. The former is also called asynchronous motor and usually relies on a small speed difference between the rotating magnetic fields of the stator, while the rotor shaft speed is called slippage in order to induce rotor current in the rotor AC winding. Therefore, induction motors cannot generate torque near induction-independent synchronous speeds, or may no longer exist.
In contrast to this situation, synchronous motors do not use slip induction mechanisms for operation because they use permanent magnets, salient poles or independently excited rotor windings instead. In this way, the synchronous motor generates its rated torque at the exactly synchronous speed which is appropriate to the situation.
In addition, the brushless wound-rotor doubly fed synchronous motor system is designed to have independently excited rotor windings, and does not rely on the physical principle of current slip induction. The brushless wound-rotor doubly fed synchronous motor is a synchronous motor that can be run at the power frequency exactly, or changed to a multiple of the power frequency instead. These are important working mechanisms for AC motors and corresponding sub types of AC motors. Besides the types of AC motors introduced, there are also eddy current motors, AC and DC mechanical commutation motors, the speed of which depends on the voltage and winding connection values.
There are also AC servo motors, which are divided into single-phase induction motors and two-phase servo motors. For single-phase induction motors, they do not have a unique rotating magnetic field like multi-phase motors. However, the magnetic field alternates between pairs of magnetic poles, which can be regarded as two magnetic fields rotating in opposite directions. They do require a secondary magnetic field, which may cause the rotor to move in a particular direction, and after starting, the alternating stator magnetic field rotates relative to the rotor.


Two Phase AC Servo Motor

Contrary to the single-phase motor, the conventional two-phase AC servo motor has a squirrel cage rotor and a magnetic field composed of two windings. These two windings are a constant voltage main winding, and the other is a control voltage winding orthogonal to the main winding. Therefore, a rotating magnetic field is generated, and reversing the phase helps the motor reverse.
Due to their convenient and stable characteristics, single-phase and two-phase motors can be widely used in industry to support a variety of power supply work, which can ensure the manufacturer's final product quality.


AC Motor and the Future

It is difficult to say the future development of motor design. Because the Ministry of Energy has been developing power sources vigorously in the past decade, various technologies have brought surprises to manufacturers and users. It is clear engineers and business owners in the industrial field will definitely find Innovative solutions for the market, and make the motor operation more and more advanced for the good for the public.

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