What are AC Motors?

There are two main types of motors which are in common use in the present day. The two types are Alternating Current motors (AC) and Direct Current motors (DC). As the two names suggest the different categories of motors require two forms of current; alternating current and direct current. Direct and alternating current indicates the way in which electricity is transferred to the motor and inside it. DC motors are subdivided into brush-less or with brushes, AC motors on the other hand can be categorized into three phase or single phase motors.

Single phase Alternating Current is the current which is normally supplied in homes; three phase electricity is supplied to places where industrial electricity standards are required. The most primitive and commonly seen AC motors are called universal motors because they can even run on Direct Current as well. Speed in which AC motors run can be changed to desired levels; therefore making it ideal for use in home appliances such as mixers, grinders and fans. Production of AC motors is very cheap making it more suitable for domestic use where not much power is required. One drawback is perhaps that AC motors are inefficient; meaning the ratio of power input to the motor against power output from the motor is less.

AC motors are made of two basic parts, a stator which is the outside stationery component with a coil wound around it with an electric current. The second component is a rotor which is attached to the output shaft. The rotating field gives a rotating motion to the rotor. Induction AC motors are larger AC motors which are fitted with capacitors to create a second phase from the supplied typical single phase electricity. Induction motors are of two types which can be capacitor starter motors or capacitor run motors. The second capacitor created phase and the initial phase of current interact to start the AC motor. Induction AC motors are made efficient and long lasting by the use of a capacitor to induce a current unlike DC motors which use brushes. Brushes tend to wear over time and are more probable to be damaged or fail easily.

These motors are rated according to their horsepower and speed. AC motors found in home use are usually less than one horse power, for example 0.5 horsepower or 0.25. Larger AC motors rated at thousands of horse power are found in factories. The unit of rating AC motors using speed is done by the help of a unit called RPM which is the rounds per minute in which the rotor spins. Unlike horsepower, the RPM decreases when a load is added on the motor. The RPM rated for a specific motor is the speed achieved when no load is applied. When there is too much load on the motor it can cause the motion to stop completely, this speed is commonly termed as stall speed.

There are many kinds of AC motors which are designed for different purposes. They are mainly good for domestic use because they are cheap, efficient and provide sufficient power. Some AC motors are used in the automotive industry as well. Hand drills, fans, Air-conditioning systems and freezers have Ac motors in them.