Alternating current motor | AC motor

AC motors or alternating current motors are electric motors that convert electrical power into mechanical power in the form of an alternating voltage.
Unlike BLDC motors (also called EC motors), there are AC motors with or without permanent magnets. The stator of an AC motor essentially consists of a package of individual electrically insulated panels, which are surrounded by the stator winding.

A phase shift brings about the electromagnetic field of rotation.
The rotor generates its own magnetic field through the windings arranged in it or, depending on the design, permanent magnets contained in the rotor; this magnetic field counteracts the stator’s field of rotation.

The electromagnetic interaction between the stator's field of rotation and the rotor field generates a torque that sets the rotor in motion.

An AC motor consists essentially of:

• Housing with junction box (terminal box)
• Stator bushing with coiled sheet metal package
• Rotor sheet package with rotor coiling or permanent magnets
• Ball bearing

For speed control, a frequency inverter or transformer is connected upstream of the AC motor.

​ Proven quality from ZIEHL-ABEGG: The ACexternal rotor motor working in combination with the Fcontrolfrequency inverter consolidates the advantages of a wear-free short-circuit rotor with the energy efficiency of an EC motor.

• Proven technology, high operational reliability: Due to their simple design, AC motors offer robust and reliable drive solutions.
• Maintenance-free design: Since AC motors are usually brushless, there is virtually no wear during operation. This means a long service life with low maintenance requirements for the user.
• AC motors are efficient: If the AC motor is activated via a frequency inverter for the purpose of speed control, its efficiency can be significantly improved in the partial load range.
• AC motors are affordable: The simple design of AC motors typically results in low manufacturing costs. In addition, wear-free operation reduces costs for repairs, spare parts, etc.

AC motors are used in a wide range of applications due to their special advantages (examples):

• Fans, blowers and ventilation systems
• Stall ventilation, agriculture
• Explosive environments
• Compressors
• Drives for production machines, grinding belts, polishing machines, conveyor belts, etc.
• Electric vehicles
• Domestic appliances

Both AC and EC (EC = electronically commuted) motors are normally operated with alternating current from the mains. However, a key difference is that AC motors (asynchronous) pass the alternating current directly to the windings, while in AC motors (synchronous) and EC motors, the alternating current is first converted to direct current and then passed on to windings.

Other examples of differences relate to both the design and function:

Each electric motor has a certain number of poles. Depending on the motor type, the number of poles varies from at least two (north and south pole) to four, six, eight or more poles. The difference between the number of poles and the number of pole pairs must be observed: A 2-pole electric motor has one pole pair, a 4-pole electric motor has two pole pairs, etc.
The poles cause the direction of magnetisation to alternate, which generates the magnetic field of rotation and thus causes the rotor to rotate.
Asynchronous motors rotate more slowly than the stator frequency proportional to the number of poles. Example: At a mains frequency of 50 Hz, a 2-pole motor runs at 3000 rpm, a 4-pole motor at 1500 rpm, etc.