DC Motor

Electric motors are devices that use electrical energy to convert it into mechanical energy, which is used in a wide range of household and industrial appliances. Electric motors can be found in various types based on the needs and type of current. Among the types of electric motors, the DC motor is specifically one that uses direct current electricity. These are highly valued for their ability to give precise control of speed and high starting torque, making them a perfect choice for applications requiring fine adjustments in speed and rotation.

1.0Basic Construction of a DC Motor

A DC motor is made up of various parts to work together to convert electrical energy into mechanical energy, which includes: 

1. Stator: It is the non-moving part of the electric motor that produces a magnetic field, usually manufactured by a permanent magnet or an electromagnet. 
2. Rotor (Armature): It is the rotating part of the DC motor which holds the winding from which the current flows. 
3. Commutator: A Commutator is a rotary switch that reverses the direction of current in the windings of the armature for constant rotation in one direction.  
4. Brushes (DC Motor Carbon Brush): Brushes maintain electrical contact with the commutator, allowing the current to flow into the armature. 
5. Shaft: It is the part which directly connects to the rotor, transmitting the mechanical energy produced by the motor. 
6. Field Windings: Windings are the coil in the stator with numerous turns. Current flows through these coils to produce a magnetic field. 
7. DC Motor Drive: A DC motor drive is an electronic system box which controls the operations of a DC motor. It typically contains a combination of switches, controllers, and sensors to ensure smooth operation and accurate control of the motor in various applications.

2.0DC Motor Principle

The DC Motors principle is the interaction of a magnetic field with electric current. With a current-carrying conductor, the armature windings, there is a resultant force exerted on the conductor when it is placed in a magnetic field. In simple words, when a current-carrying conductor is kept within a range of magnetic fields, it gains torque and starts to move. 

Lorentz force and Flemings's left-hand rule are the laws followed by the DC Motor to find the direction and symmetry of force produced by this interaction. 

3.0The Working of DC Motor

The DC Motor working is based on the principle of electromagnetism, in which when a current-carrying conductor is placed within a magnetic field, the conductor experiences a force that causes motion in the conductor. Here’s how a DC motor works: 

• Current Flow: DC voltage is applied to the armature windings, which causes current to flow through them.
• Magnetic Field Interaction: A magnetic field is produced by the applied current that interacts with the stator’s magnetic field.
• Force on Armature (Lorentz Force): The interaction between the magnetic field of both the armature and stator creates a force, producing torque or the force that rotates the armature casing motion.
• Commutator Action: As mentioned previously, the commutator reverses the current direction in the armature windings as it rotates. Hence, the current will be reversed by the commutator, ensuring continuous rotation in the same direction.
• Fleming’s Left Hand Rule: This law is used to determine the direction of the force or motion of the coil as:

Thumb = direction of motion (torque)

Forefinger = direction of magnetic field

Middle finger = direction of current

4.0DC Motor Types

According to specific needs and features, DC motors can be divided into various types, which are: 

1. Brushless DC Motor (BLDC): As the name suggests it is a type of DC motor which doesn’t consist of a brush. As compared to conventional brushed DC motors, it is more efficient and requires less maintenance since it switches the current in the stator using electronic controllers and permanent magnets in the rotor.
2. Permanent Magnet DC Motor: The Stator in this type of motor is made up of permanent magnets instead of electromagnets, which makes the design simpler and smaller, perfect for small devices such as fans and toys. 
3. Compound DC Motor: This type of motor is perfect for appliances where high torque and speed control are both important, as it is specifically designed to produce high starting torque while maintaining good speed. 
4. DC Motor Separately Excited: Unlike conventional DC motors, the field windings in this type of motor are powered by a separate external source meaning it doesn’t depend on the armature current. 
5. Small DC Motor: As clear from the name itself, it refers to a DC motor that is small and compact and compatible with low-power appliances like toys, small fans, and handheld devices. 
6. High Torque DC Motor: It is a type of DC motor specifically designed to work where large amounts of rotational force or torque at low speed are needed. It is perfect for devices with heavy loads, such as electric vehicles, cranes, and winches. 

5.0DC Motor Uses

DC Motors are used in a wide array of applications, from small devices to some of the best and high-end devices. Some of the uses of DC motors are: 

• In Electric vehicles like electric cars and cranes, DC motors are specifically used to give a high torque at low and precise speed.
• Conveyor belt systems in supermarkets and other industries for material handling are operated with DC motors. 
• Fans and blowers are also controlled and operated by DC motors. 
• DC motors have a great use in robotics in controlling movement and actuators for precise and controlled speed and direction of the movement. 
• Motion in the wheel of model trains is also controlled by small DC motors for precision and accuracy in the speed.