WAZIPOINT Engineering Science & Technology: Motor Principle and DC Motor Construction

Sunday, November 5, 2023

Motor Principle and DC Motor Construction

The motor principle, often referred to as the motor principle of operation, is a fundamental concept in physics and engineering that explains how electric motors work. It's based on the interaction between magnetic fields and electrical currents, and it forms the basis for the operation of various types of electric motors, such as DC (direct current) motors and AC (alternating current) motors. To define the motor principle, you can describe it as follows:

What is the DC Working Motor Principle?
Principle of Motor
Fig-1: Motor Principle

N- North Pole of Magnet,

S- South Pole of Magnet,

M- Motion of Rotation.

The motor principle is the fundamental concept that electric motors operate by generating a magnetic field and harnessing the interaction between this magnetic field and an electrical current to produce mechanical motion. In simple terms, it states that when an electrical current flows through a wire or coil placed within a magnetic field, a force is exerted on the wire or coil, causing it to move. This movement is the basis for the mechanical rotation or motion produced by electric motors.

How Your DC Motor Work?

An Electric motor is a machine that converts electric energy into mechanical energy. Referring to the figure above, its action is based on the principle that when a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force whose direction is given by Fleming’s Left-hand Rule and whose magnitude is given by 

F = BIl Newton.

Constructionally, there is no basic difference between a d.c. generator and a D.C. motor. In fact, the same D.C. machine can be used interchangeably as a generator or as a motor. D.C. motors are also like generators, shunt-wound, series-wound, or compound-wound.

In Fig-2  a part of multipolar d.c. the motor is shown. When its field magnets are excited and its armature conductors are supplied with current from the supply mains, they experience a force tending to rotate the armature. Armature conductors under N-pole are assumed to carry current downwards (crosses) and those under S-poles, are to carry current upwards (dots). 

Motor Working Principle
Fig-2: Motor Working Principle

By applying Fleming’s Left-hand Rule, the direction of the force on each conductor can be found. It is shown by small arrows placed above each conductor. It will be seen that each conductor can be found. It will be seen that each conductor experiences a force F which tends to rotate the armature in the anticlockwise direction. 

These forces collectively produce a driving torque which sets the armature rotating. It should be noted that the function of a commutator in the motor is the same as in a generator. 

By reversing the current in each conductor as it passes from one pole to another, it helps to develop a continuous and unidirectional torque.

Key Points Connection in Motor Working Principle

Key points to include in your definition of the motor principle:

Magnetic Field: Electric motors consist of one or more magnets or coils that create a magnetic field within the motor.

Electrical Current: An electrical current is supplied to the motor through conductive wires or coils.

Magnetic Interaction: When the electrical current flows through the wire or coil within the magnetic field, it generates a force, known as the Lorentz force, which causes the wire or coil to move.

Mechanical Motion: The movement of the wire or coil is then used to rotate a shaft or perform other mechanical tasks, such as turning a fan, spinning a rotor, or driving a conveyor belt.

Relation between Magnetic Field, Electrical Current, Magnetic Interaction, and Mechanical Motion in Motor Engineering

In motor engineering, there is a close relationship between magnetic fields, electrical current, magnetic interaction, and mechanical motion. This relationship is fundamental to the operation of electric motors, which convert electrical energy into mechanical motion through the interaction of magnetic fields.

Here's how these elements are interconnected in the context of motor engineering:

Magnetic Field and Motor Principle:

Electric motors rely on the presence of magnetic fields to function. Magnetic fields are created when an electric current flows through a wire or a coil. These magnetic fields are essential for the operation of motors.

Electrical Current and Motor Principle:

Electrical current is the flow of electric charge, typically through a conductor like a wire. In an electric motor, electrical current is supplied to the motor's windings or coils. When current flows through these windings, it generates a magnetic field according to Ampere's law.

Magnetic Interaction and Motor Principle:

The interaction between magnetic fields is a fundamental principle of motor operation. In an electric motor, there are typically two main components with magnetic fields: the stator and the rotor. The stator has stationary windings that produce a magnetic field, while the rotor has conductive bars or coils that can rotate within this field. This interaction between the stator's magnetic field and the rotor's conductive elements creates a mechanical force.

Mechanical Motion and Motor Principle:

The interaction between the magnetic fields generated by the stator and rotor results in mechanical motion. This is the basic principle of motor operation. As the rotor is subjected to magnetic forces, it experiences a torque that causes it to rotate. This rotational motion can be used to perform mechanical work, such as driving a fan, moving a conveyor belt, or turning the wheels of a vehicle.

In summary, the key relationship in motor engineering involves the generation of magnetic fields through electrical current, the interaction of these magnetic fields between the stator and rotor, and the resulting mechanical motion. Electric motors come in various types, such as DC motors, AC motors, and various specialized designs, but they all rely on these fundamental principles to convert electrical energy into mechanical motion efficiently. The specific design and operation of motors can vary, but the core principles of magnetic interaction and electrical current are consistent across different motor types.

READ: Types of AC and DC Motors 

Conversion of Electrical Energy to Mechanical Energy by DC Motor

The D.C motor principle demonstrates the conversion of electrical energy into mechanical energy, making electric motors a vital component in various applications, from household appliances to industrial machinery.

It's important to note that there are various types of electric motors, including DC motors and AC motors, each with its own specific design and operation principles, but the fundamental concept of the motor principle applies to all of them.

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