Types of Motors: AC and DC Motors & Applications

Types of motors are electrical devices that convert electrical energy into  mechanical energy. It works on the principle that when we place a current conductor in a magnetic field, the engine of the motor transforms into an electrochemical system, thereby, converting electrical energy into mechanical energy. The electric motors can be broadly classified as AC and DC Motors. AC motors have good speed control whereas DC Motors are usually preferred owing to their low initial cost.

Read More: AC and DC Motors

Key Terms: Electric Motor, AC, DC, Electric Field, Magnetic Field, Current, Voltage, Synchronous, Asynchronous

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What is a Motor?

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A motor is a mechanical device that gives rise to mechanical energy by converting electrical energy. When the current and the magnetic field in the motor interact with each other, a force is experienced in a direction that is perpendicular to the current and the magnetic field. A motor is a device that generates rotational force.

Electric motors are further classified based on their application as follows:

• AC Motors
• Dc Motors

​Let us look at each of these and their types in detail below.

Read More: Electromagnetic Induction Important Questions

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Types of Motors

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AC motors demand low power initially and are flexible for speed control, DC motors, however, can be easily installed and have low initial costs of power units and thus are widely used. The AC and DC motors can further be classified as:

AC Motors

1. Synchronous Motors
2. Asynchronous Motors (Induction)

The further classifciation of thes etwo types are discussed further in the article.

DC Motors

1. Brushless
2. Brushed

The following flow chart gives information on the broad classification of the types of motors.

Read More: Universal Motors

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AC Motors

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AC Motor has many flexible features and has a larger installed base as compared to DC Motors. Some of their features are:

• AC Motors demand low power on start. 
• The starting current in AC motors can be controlled.
• They are also highly flexible in speed control.
• They have adjustable torque limits.
• The operational speeds of AC motors can be adjusted.
• They have controlled acceleration while working.
• They can reduce power line disturbances.

Types of AC Motor

The following are the broad classification of the types of AC Motors:

Synchronous 

The speed of synchronous AC motors remains constant even with varying loads of current and the rotor’s rotation is synchronized with the frequency of the supply current. Due to this advantage, this type of motor is ideal for moving pieces of equipment at a constant speed and is used in positioning devices that need high precision such as machines, instrumentation, robots, etc.

Asynchronous (Induction)

The engine of the AC induction motor works on the principle of electromagnetic induction. Due to their load capacity, these motors are the type of AC motor that is widely used. The induction is generated from the stator’s magnetic field which results in the production of an electric current and a torque. They are further classified into two types:

• Single-Phase Motors

They are generally used in household appliances where smaller loads are required.

• Triple-Phase Motors

They are used in industries for various applications such as lifting gears, conveyor belts, etc. 

Also Read: Torque Vs Moment

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DC Motors

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DC Motors were the first type of motors that were commonly used due to their low initial costs which included drives and motors as compared to AC motors. However, for high power situations, the total maintenance costs of the system arose. Some of the features of DC motors are:

• The speed of the DC motor can be controlled by varying the voltage supplied.
• They can be easily installed.
• Their speed-torque curve is linear.
• They can be started, stopped, reversed, or accelerated quickly.
• DC motors provide speed control for a wide range.
• They have a high starting torque.

Types of DC Motor

DC Motors are broadly classified further as brushless and brushed DC Motors. Let us look at them in detail below.

Brushless Motors

Some of the characteristics properties of Brushed DC Motors are as follows:

• Brushless DC Motors have a longer life span and a simpler design.

• They require little maintenance and are highly efficient.

• They are used in appliances where position and speed control is required such as in fans, pumps, compressors, etc.

• Stepper motors are an example of brushless motor design.

Brushed Motors

Brushed Motors are traditionally used for a variety of basic applications. Some of them are:

•  They are used in appliances where a simple control system is observed.

• They are used for basic industrial applications and consumer use.

These are further classified into four types which are:

Series Wound

Some of the interesting characteristic properties of series wound motors are:

• The field winding and the series winding are connected in series.
• The speed of the motor can be controlled by varying the voltage supplied. However, the motor offers poor control of speed and the speed can drop as the torque increases.
• These motors are widely used in lifts and cranes, automotive, hoists, etc. due to their high initial torque.

Shunt Wound

The importaant properties of Shunt Wound DC Motors are:

• The field winding and the series winding are connected parallelly to each other.
• It has one supply voltage and can deliver high torque without any speed reduction through increasing the current to the engine.
• For its medium starting torque with respect to constant speed, it is used in vacuum cleaners, grinders, conveyors, etc.

Compound Wound

Some of the interesting properties are:

• Compound Wound DC Motor is a combination of the Series and Shunt Wound Motors.
• Here, in the polarity of the series field, the polarity of shunt winding is also added.
• It runs smoothly even when the load on the system varies.
• It has higher initial torque and is used in circular saws, rotary presses, centrifugal pumps, elevators, etc.

Permanent Magnet

Permanent Magnet is used in situations where precise control is required and low torque is used such as servo systems, robotics, etc.

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Things to Remember

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• An electrical motor is a device that converts electrical energy into a mechanical energy.
• A motor is a device that generates rotational force.
• Motors are primarily classified into two types, that is AC motor and DC motor.
• AC motors demand low power initially and are flexible for speed control
• DC motors can be easily installed and have low initial costs of power units.
• The speed of synchronous AC motors remains constant even with varying loads of current
• The engine of the AC induction motor works on the principle of electromagnetic induction.
• Brushless DC Motors have a longer life span and a simpler design.
• Brushed DC Motors are traditionally used in appliances where a simple control system is observed.

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