In 1882, Nikola Tesla made an important discovery: the rotating magnetic field. Tesla later pioneered the use of a rotary field of force to operate machinery. He exploited the principle to design a unique two-phase induction motors in 1883. In 1885, Galileo Ferraris independently researched the very same concept. Ferraris published his research in a paper in 1888, to the Royal Academy of Sciences in Turin. In Tesla's published articles, he had suggested that the commutators from a machine could be removed and the device could operate on a rotary field of force. Professor Poeschel, Tesla's teacher, stated that would be akin to building a perpetual motion machine. This classic alternating current electro-magnetic motor was the beginning of the induction AC motors. Michail Osipovich Dolivo-Dobrovolsky later invented a three-phase "cage-rotor" in 1890. These types of AC motors are now used for the vast majority of commercial and industrial applications.

A typical AC motor consists of two parts:
• An outside stationary stator having coils supplied with AC current to produce a rotating magnetic field, and;
• An inside rotor attached to the output shaft of AC Motors that is given a torque by the rotating field.

The AC Motors come in two different types known as Induction and Synchronous. These AC Motor types are determined by which rotor is used in the construction.

Induction AC Motors
Induction AC Motor products can be referred to as asynchronous motors or rotating transformers. These types of AC Motors use an electromagnetic induction to power the rotating device which is usually the shaft. The rotor in Induction AC Motors typically turns slower than the frequency that is supplied to it. Induced current is what causes the magnetic field that envelops the rotor of these motors. These Induction AC Motors can come in one or three phases.

Synchronous AC Motors
The Synchronous Motors are typically AC Motors that have their rotor spinning at the same rate as the alternating current that is being supplied to it. The rotor can also turn at a sub multiple of the current it is supplied. Slip rings or a permanent magnet supplied with current is what generates the magnetic field around the rotor.

AC Motors are a reasonable cost effective solution to your application needs. The construction materials along with how the motor is designed make AC Motors an affordable solution. The AC Motors operate with a rotating magnetic field and does not use brushes. This enables the cost of the motors to be lower and eliminates a piece of your motor that wears over time. AC Motors do not require a driver to operate. This saves initial setup costs. Today's manufacturing processes makes producing AC Motors easier and quicker than ever. The stator is made out of thin laminations that can be pressed or punched out of a machine. Many other parts can be quickly made and perfected saving both time and money.

AC Motors have two options for feedback controls. These options are either an AC Motor resolver or an AC Motor encoder. Both the AC Motor resolver and the AC Motor encoder can sense direction, speed, and the position of the output shaft. While both the AC Motor resolver and AC Motor encoder offer the same solution in multiple applications, they are greatly different.

AC Motor resolvers use a second set of stator coils called the transformer to provoke rotor voltages across an air gap. Since the resolver lacks electronic components, it is very tough with a large temperature range. The AC Motor resolver is also naturally shock resistant due to how it is designed which makes it most likely used in harsh environments.

The AC Motor optical encoder uses a shutter that rotates to disrupt a beam of light that crosses the air gap between a light source and the photo detector. The rotating of the shutter over time causes wear on the encoder. This wear reduces the durability and dependably of the optical encoder.

The type of application being run will establish whether a resolver or an encoder is needed. AC Motor encoders are easier to implement and are more exact so they should be the primary preference for any application. A resolver should only be chosen if the durability needs and the environment in which it will be used requires it.

AC Induction motors have been in the industry for over 20 years now. The idea behind AC Motors came from Nikola Telsa in the 1880's. Nikola Telsa stated that motors do not need brushes for the rotor to commutate. He said they could be induced by a rotating magnetic field. Nikola Telsa identified the use of alternating current which induced rotating magnetic fields. Telsa filed the U.S. patent number 416,194 for his work on AC Motors. This type of motor is what we call an AC Induction motor today.

AC Motors have made a name for itself by having a simple design, being easy to use, having a simple rugged construction and being cost effective for many different applications. Advances in technology have allowed manufacturers to build up Telsa's idea and have allowed a great versatility in the speed control of AC Induction Motors. From a simple phase control to more robust closed loop systems that use vector oriented field controls; AC Motors have advanced over the last one hundred and twenty years.

There is a vast selection of accessories for AC Motors. The accessories available include a brake, clutch, fan, connector, and cables.

The AC Motor brakes are a 24vdc system. These brakes are ideal for any holding applications you may use with AC Motors. The AC Motor brakes have a low voltage design for applications that are susceptible to weak battery, brown out, or long wiring.

The AC Motor Clutch is used to control the torque that is applied to the load. The AC Motor clutch can also be used to ramp up the speed of a high inertia load. Clutches are ideal to use with AC motors when you want precise control over torque or to slowly apply the power. AC Motor clutches also help prevent large current spikes.

AC Motor Fans are used to cool down the motors. They are not really seen in small motors because they are not needed but more common with larger AC induction motors due to heat generation. There are two types of fans that are used for AC Motors. The types are internal and external fans. AC Motor fans are ideal to use when overheating is a concern.

AC Motor cables can be custom made with the supplied AC motor connector to fit your specifications. The cables may also be purchased from Anaheim Automation.

Anaheim Automation offers a wide selection of options to customize your AC motor. The options available to customize include but are not limited to: shaft, brake, mounting dimensions, speed, and torque. Please feel free to give Anaheim Automation a call for any custom applications in which AC Motor products are required.

The most common and simple industrial motor is the three-phase AC induction motor, sometimes shortened to AC Motor. Pertinent information can be found about AC motors by checking the nameplate.

Advantages of Using AC Motors

• AC Motors are of a simple design
         • The simple design AC motors: Simply stated, a series of three windings in the exterior stator section with a simple rotating section (rotor). The changing field caused by the 50 or 60 Hertz AC line voltage causes the AC motor rotor to rotate around the axis of the motor.
         • The speed of AC motors will depend upon these three variables:
                   1. The fixed number of winding sets (poles) built into AC motors, which determines the motor's base speed.
                    2. The frequency of the AC line voltage. Variable speed drives change this frequency to change the speed of AC motors.
                    3. The amount of torque loading on AC motors, causes slipping.
• AC Motors are of a low cost construction
AC motors have the advantage of being the lowest cost motor. AC motors are perfect for applications requiring more than about 1/2 hp (325 watts) of power. This is due to the simple design of AC motors. For this reason, AC motors are generally preferred for fixed-speed applications, such as in industrial applications and for commercial and domestic applications where AC line power can be easily attached. Over 90% of all motors are AC induction motors. They are found in air conditioners, washers, dryers, industrial machinery, fans, blowers, vacuum cleaners, and many, many other applications.

• AC Motors operate reliably
The very simple design and construction of AC motors casue them to be extremely reliable and are considered to be low maintenance. Unlike DC Brush Motors, there are no brushes to replace. If AC Motors are used in the appropriate environment, protected by an enclosure, AC motors can expect to replace the bearings after several years of continuous operation. If the application is well designed in a protective environment, AC motors may not require the bearings to be replaced for more than 10 years.

• Easily Found Replacements
The wide use of AC motors in many different industries has resulted in easily found replacements for existing equipment repairs and/or upgrades. Many manufacturers adhere to either European (metric) or American (NEMA) standards.
• AC Motors are made by many manufacturers , so it is relatively easy to obtain replacements (for basically the same motor)
• AC Motors are designed in a variety of mounting styles (dependent upon the motor manufacturer). Foot Mount, C-Face, Large Flange, Vertical and Specialty.
• There are many environmental styles available for AC Motors, to cover a wide range of applications and industries, called Specialty AC Motors by most. Because of the wide range of environments in which people want to use AC motors, manufacturers have adapted by providing a wide range of packaging/enclosure designs, such as Open Drip Proof (ODP), Totally Enclosed/Fan-Cooled (TEFC), Totally Enclosed/Air-Over (TEAO), Totally Enclosed/Blower-Cooled (TEBC), Totally Enclosed/Non-Ventilated (TENV), and Totally Enclosed/Water-Cooled (TEWC) versions.

Disadvantages of Using AC Motors

• Expensive speed control - Speed controllers can be expensive. The electronics required to handle an AC inverter driver are considerably more expensive than those required to handle a DC motor. However, if performance requirements can be met ~meaning that the required speed range is over 1/3rd of base speed ~ AC inverters and AC motors are usually more cost-effective overall, than are DC motors and DC drives. This is especially true for applications larger than 10 horsepower, because of cost savings in the AC motor.
• Inability to operate at low speeds - Standard AC motors should not be operated at speeds less than about 1/3rd of the base speed, due to thermal considerations. A DC motor should be considered for these applications.
• Poor positioning control - Positioning drivers and controllers can be expensive and crude. Even a vector drive is very crude when controlling a standard AC motor. Stepper motors and Servo Motors are more appropriate for applications wherein positioning and speed control is critical.