Types of Motors

What is an Electrical Motor

The engine or electric motor is a device that has provided one of the biggest advancements in engineering and technology ever since the advent of electricity. An electric motor is a machine that converts electrical energy to mechanical energy. The behaviour is based on the idea that when a current conductor is placed in a magnetic field, the engine is nothing but an electromechanical system that converts electrical energy into mechanical energy.

In simple words, we can conclude that a system that generates rotational force is a motor. The very basic principle of the functioning of the electric motor lies in the fact that the force is experienced in the direction perpendicular to the magnetic field and the current when the field and the current are made to interact with each other.

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Classification of Motors or Different Types of Motor

The primary classification of the motor or motor type can be tabulated as shown below -

AC Motors

AC motors have a much larger installed base than DC motors, and are highly flexible in many features, including speed control (VSD-Variable Speed Drives). Some of the major benefits are:

• Low power demand on start

• Controlled acceleration

• Adjustable operational speed

• Controlled starting current

• Adjustable torque limit

• Reduced power line disturbances

Types of AC Motor Include:

Synchronous

In this type of engine, the rotation of the rotor is synchronized with the frequency of the supply current and the speed stays constant under varying loads, making it suitable for moving equipment at a constant speed and used in high-precision positioning devices such as robots, instrumentation, machines and process control.

Induction (Asynchronous)

This type of engine uses electromagnetic induction from the magnetic field of the stator winding to produce an electrical current in the rotor and therefore in the torque. They are the most common type of AC motor and are important in the industry due to their load capacity.

DC Motors

DC motors were the first type of engine commonly used and the initial costs of the systems (motors and drives) appear to be usually lower than AC systems for low power units, but with higher power, the total maintenance costs rise and should be taken into account. DC Motor speed can be controlled by varying the supply voltage and is available in a wide range of voltages, although the most common form is 12 & 24V, with some of the advantages being:

• Easy installation

• Speed control over a wide range

• Quick Starting, Stopping, Reversing and Acceleration

• High Starting Torque

• Linear speed-torque curve

DC Motors are commonly used and it can be used from small tools and appliances to electric vehicles, lifts and hoists.

The two common types of dc motor are -

Brushed

These are the extra traditional type of engine and are generally used in value-sensitive applications where the monitoring system is incredibly easy, such as for consumer applications and more fundamental industrial equipment, such types of engines can be broken down as -

• Series Wound – This is where the field winding is connected in series with the rotor winding and the speed control is by varying the supply voltage, but this type offers poor speed control, and, as the engine torque increases, the speed drops. Applications include automotive, hoists, lifts and cranes, as they have a high starting torque.

• Shunt Wound – This type has one supply voltage and the field winding is linked parallel to the winding of the rotor and can deliver increased torque without reducing the speed by increasing the engine current. It has a medium starting torque with constant speed, so suitable for applications include lathes, vacuum cleaners, conveyors, and grinders.

• Compound Wound – This is a cumulative of the Series and Shunt, where the polarity of the shunt winding is such that it adds to the field series. This type has a high starting torque and runs smoothly when the load varies slightly and is used for driving compressors, circular saws, scissors, variable-head centrifugal pumps, rotary presses, circular saws, scissors, elevators, and continuous conveyors.

• Permanent Magnet – As the name suggests, a permanent magnet is used instead of an electromagnet and is used in applications where precise control and low torque are used, such as robotics, servo systems.

The benefits of this system are long life, low maintenance, and high performance (85-90 per cent), while the drawbacks are higher initial costs and more complex controls. These types of engines are generally used for speed and position control with applications such as fans, pumps, and compressors, where reliability and robustness are required. There is an example of a brushless design in Stepper Motors.