# Basic parts of a DC motor

What is a DC motor?

A direct current motor, also known as a DC motor, is an electrical machine that converts electrical energy into mechanical energy by creating a magnetic field generated by a direct current. When a direct current motor is turned on, a magnetic field is formed in the stator. The magnetic field attracts and repels magnets on the rotor, causing it to rotate. The commutator, which is attached to brushes connected to the power source, supplies current to the motor’s wire windings to maintain the rotor turning continuously.

Working of a DC Motor

A direct current motor operates on the idea that when a current-carrying conductor is placed in a magnetic field, it feels a magnetic force whose direction is determined by Fleming’s Left-hand Rule. In other words, the DC motor spins as a result of the interaction of the magnetic field of the permanent magnet with the magnetic field of the current-carrying electromagnet.

Fleming’s Left-Hand Rule

This rule states that if the thumb, forefinger, and middle finger of the left hand are stretched in such a way that they form a right angle to each other and the forefinger points in the direction of the magnetic field, the middle finger in the direction of current flow, then the thumb will point in the direction of force acting on the conductor.

F = BIL Newtons

Where,

B = magnetic flux density

I = current

L =conductor’s length within the magnetic field.

Back EMF

The interaction of the current-carrying conductor with the changing magnetic field produced by the field winding results in the generation of an EMF in the conductor. This EMF operates in the inverse direction of the applied voltage. Back EMF refers to the induced EMF in the motor.

The magnitude of back EMF is directly proportional to motor speed. Consider a DC motor whose load is abruptly lowered. The required torque in this situation will be little in comparison to the existing torque. Because of the additional torque, the motor’s speed will begin to increase. As a result, the magnitude of the back EMF will grow proportionally to the speed. As the back EMF increases, the armature current begins to decrease. As the back EMF increases, the armature current begins to decrease. Because torque is related to armature current, it will drop until it is sufficient for the load. Thus we can control the speed of the motor.

A DC motor, on the other hand, will experience a drop in speed if it is rapidly loaded. As the speed lowers, so does the back EMF, allowing for a higher armature current. Torque will increase to meet the load requirement as armature current increases.

Parts of the DC Motor

The parts of the DC motor are listed below:

• Brushes
• Stator
• Rotor
• Yoke
• Poles
• Field Windings
• Armature Windings
• DC Motor Commutator

Brushes

Brushes serve as a bridge between the supply circuit and the rotor by being attached to the commutator. Brushes are often constructed of carbon or graphite.

Stator

The term “stationary” refers to the electrical stationary portions of a dc motor. When a voltage is delivered to the stator, it creates a magnetic field around the rotor, causing it to rotate.

The stator is made of:

• Yoke or frame
• Field windings
• Poles

Rotor

The rotor is derived from the word “rotate,” and refers to the electrically rotating component of a dc motor. A dc motor’s rotor is one of its moving elements. When a voltage is applied to the armature winding, it moves dynamically. This will generate mechanical motion for a dc motor.

This is one of the most crucial components of a dc motor. The rotor is made of:

• Shaft
• Core of the armature
• Brush
• Commutator
• Windings of the armature

Yoke

The magnetic frame or yoke of a direct current motor is built of cast iron or steel and is an essential part of the stator or static part of the motor.

Its primary duty is to safeguard the sophisticated inner workings of the motor and to support the armature. It also aids the field system by containing the DC motor’s magnetic poles and field winding.

Poles

DC motors have magnetic poles that fit into the inside wall of the Yoke and are tightened with screws. Poles are made up of two components: the Pole Core and the Pole Shoe. These two pieces are connected to the Yoke and are held together by hydraulic pressure. Based on its design, each part of the Poles has a specific duty. The Pole Shoe is meant to carry slots for the field windings as well as distribute the flux formed by the field windings into the air gap between the rotor and stator, and it is held above the Yoke by the core. It assists in reducing the loss caused by reluctance.

Field Windings

The copper wire field windings that circle the Pole Shoes are composed of copper wire. The field winding is utilised to energise the stator’s static magnetic field. The field windings are installed around the slot of the Pole Shoes. If we employ permanent magnets, like in a Permanent Magnet Motor or PMDC motor, we don’t need field windings.

Armature Windings

Armature winding is another DC motor component. The armature winding of a DC motor is made up of two types: lap winding and wave winding. The number of parallel pathways distinguishes them. Armature Winding is coupled to the rotor and adjusts the magnetic field along its rotational path. Magnetic losses are the result of this technique. Designers attempt to reduce magnetic losses by laminating the armature core with low-hysteresis silicon steel. The laminated steel sheets will next be stacked together to form the cylindrical construction of the armature core. The same material is used to create slots inside the armature core.

DC Motor Commutator

The coils on the armature are terminated and interconnected by the commutator, which is made up of a number of insulated bars or commutator segments. The commutator rotates with the rotor and serves to rectify the A.C. induced voltage and current in the armature.

Applications of DC Motors

DC series motors are appropriate for high and low-power drives and they can be used for both fixed and variable-speed electric drives. It is also simple to design and maintain.

DC Motors can be used in the automobile industry due to its simple design, such as

• Cranes, air compressors, and elevators
• Electric traction winching system
• Hair dryer, vacuum cleaner, and power equipment with speed control
• Machine for sewing
• Electric foundation