In the late 1800s, the actual invention of the AC motor was made by Nikola Tesla. Before Tesla’s time, DC motors had been produced in small quantities, but it was his development of the versatile and rugged AC motor that opened a new age of automation and industrial productivity. AC motors are often used in areas where the speed and operating torque are fixed and are directly powered by mains voltage. They are designed to have a long working life, necessary for many applications. If you want to learn other benefits of AC motors, keep on reading.
Advantages of AC motors
The followings are the benefits of AC motors:
Variety of models
Industry builds ac motors in different sizes, shapes, and ratings for many different types of jobs. These motors are designed for use with either polyphase or single-phase power systems. By matching the type of motor to the appropriate application, increased equipment performance can be obtained. AC motors are the workhorses of industry and are produced in highly standardized frame sizes, making them nearly completely interchangeable between manufacturers.
AC motors include 3-phase and single-phase types. 3-phase AC induction motors are the most widely used motors in industrial and commercial applications. They are divided into two sub-categories:
- Squirrel cage motors
- Wound rotor motors
3-phase Synchronous motors are most commonly used in very large industrial applications or where exact speed is required. Single-phase induction motors are used where three-phase power is not available; typically, in residential, commercial, and agricultural applications. They are also used in applications with power requirements below 1 horsepower (HP). The main sub-categories include:
- Split phase
- Capacitor run
- Capacitor start
- Capacitor start – capacitor run
- Shaded pole
- Universal motors
The simple design of the AC motor results in extremely reliable, low-maintenance operation. Unlike the DC motor, there are no brushes to replace. If it works in the appropriate environment for its enclosure, the AC motor can expect to need new bearings after several years of operation. If the application is well designed, an AC motor may not need new bearings for years.
In general, ac motors are cheaper than dc motors. Almost 90% of the motors in the industry are AC motors. That’s why their production costs are lower.
Less noise and vibration
Due to the enhancement of quality standards such as places and conditions for motors to use, low noise and low vibration are required. Excessive vibration can shorten bearing life and reduce motor efficiency. Vibration can also be a result of worn bearings. AC motors generate less noise and vibration.
High durability and long lifespan
AC electric motors have high durability because they do not have brushes. Brushes can wear down easily and may need more regular maintenance. As AC motors do not have this problem, this means they have a long lifespan. It also eliminates the problem of dangerous sparking. For this reason, AC motors are preferred for fixed-speed applications in industrial applications and for commercial and domestic applications where AC line power can be easily attached.
Low power required for start-up
AC motors can distribute their power more evenly and can maintain a consistent level of power throughout their operation. It also decreases the chance of burnout, which can occur when a motor is overloaded at the start-up.
AC motors allow for steady and controlled acceleration which is key for many demanding applications. It also reduces wear and tear as speeds are not increasing and decreasing abruptly, therefore placing less pressure on the motor. Controlled acceleration is particularly important where speed must remain stable and constant to ensure it performs as it should.
Efficiency and productivity
AC motors are now capable of handling significantly higher peak current, resulting in a dramatic increase in torque and speed while reducing the overall size of the unit. This allows AC units to quickly accelerate to full speed, thereby improving operator efficiency and productivity.
AC electric motors produce less heat due to friction and no emissions and exhaust fumes. This helps to improve the overall air quality, reduces ambient noise and vibration, and limits damage to products.
The other advantage of the AC motor is the speed. The torque characteristic of the AC motor is very close to the ideal characteristic. In recent years, the development of power semiconductors and microprocessors has brought efficient adjustable speed control to AC motors through the use of inverter drives. Through this technology, the most recent designs of so-called pulse-width modulated AC drives are capable of speed and torque regulation that equals or closely approximates direct current systems.
High power factor
The power factor of an AC electrical power system is defined as the ratio of the real power flowing to the load to the apparent power in the circuit. A load with a low power factor draws more current than a load with a high-power factor for the same amount of useful power transferred. Higher currents increase the energy lost in the distribution system and require larger wires and other equipment. There are two basic methods for improving the power factor of a motor for a particular application:
- Purchase an AC motor with an inherently high-power factor.
- Install power factor correction capacitors.
Heat control options
A major consideration in both motor design and application is heat. Excessive heat will accelerate motor insulation deterioration and cause premature insulation failure. Excessive heat may also cause a breakdown of bearing grease, thus damaging the bearing system of a motor. The total temperature a motor must withstand is the result of two factors: external, or ambient temperature; and internal, or motor temperature rise. The heat of the AC motor can easily be controlled by internal and external devices.
Reversible AC motors are ideal for applications where the bidirectional operation is repeated frequently. By incorporating a simple brake and increasing the starting torque, it is possible to switch the direction of motor rotation instantaneously.