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What Is A DC Motor And What Are The Components OF A DC Motor

What Is A DC Motor And What Are The Components OF A DC Motor

November 02 , 2023 0

I.Dc Motor Concept

A DC motor is an electric motor that runs on direct current, and its main operation relies on simple electromagnetism. A current-carrying conductor will generate a magnetic field, and then when placed in an external magnetic field, it will encounter a force proportional to the current in the conductor and the strength of the external magnetic field. It is a device that converts electrical energy into mechanical energy and works by subjecting a current-carrying conductor placed in a magnetic field to a force that causes it to rotate relative to its original position. A practical DC motor consists of an exciting winding that provides magnetic flux and an armature that acts as a conductor.

The input of a brushless DC motor is current/voltage, and the output is torque. It is very simple to understand the operation of the DC motor from the basic diagram below. The DC motor basically consists of two main parts. The rotating part is called the rotor, and the stationary part is also called the stator. The rotor rotates relative to the stator.
The rotor consists of a winding that is electrically connected to a commutator. The geometry of the brush, commutator contacts, and rotor winding makes it so that when powered on, the polarity of the powered winding and the stator magnet do not align, and the rotor will turn until it is almost aligned with the stator's sulfonate field magnet.
With the rotor aligned, the brush moves to the next commutator contact and energizes the next winding. Rotation reverses the direction of the current through the rotor winding, causing the rotor magnetic field to flip to drive it to continue rotating.

II.The Structure OF DC Motor

The structure of the DC motor is shown in the following figure, before knowing its working process, it is very important to understand its design, the basic components of the motor include armature and stator

The armature black is the rotating part and the stationary part is the stator. In this case, the armature coil is connected to a DC power supply that includes a brush and a commutator. The main function of the commutator is to convert alternating current into direct current induced in the electric power. A brush can be used to provide current from the rotating part of the motor to an inactive external load. The armature can be arranged between the two poles of the electromagnet or permanently.

III.Dc Motor Parts

In DC motors, there are a variety of popular motor designs to choose from, such as brushless, permanent magnet, series, compound winding, shunt or stable shunt. Generally speaking, in these popular designs, the parts of the DC motor are the same, and the entire operation is the same. The main components of DC motor include the following
Stator, a stationary component such as a stator, is one of the components in the DC motor components, which includes the field winding, the main function is to obtain supply.

Rotor; The rotor is the dynamic part of the motor that produces the mechanical rotation of the device.
A brush; The brush using the commutator is mainly used as a bridge to fix the fixed circuit to the rotor.
Commutator: It is an open ring with a copper section design and is one of the most important components of the DC motor.
Excitation winding; These windings are made of exciting coils called copper wires.
Armature winding; The structure of these windings in DC motors has two types, such as Lap and Wave.
The magnetic pole; The magnetic pole in the motor consists of two main parts, such as the magnetic pole core and the pole shoe, which are connected together by liquid pressure and connected to the choke. Teeth/grooves; A non-conductive slot liner is often stuck between the slot wall and the coil to ensure safety from scratch, mechanical support, and additional electrical insulation. The magnetic material between the slots is called the teeth.
Motor housing; The motor housing provides support for the brushes, bearings and iron core.

IV.Working Principle OF DC Motor

The motor used to convert electrical energy from electrical to mechanical energy is called a DC motor and works on the principle that when the current-carrying conductor is located in a magnetic field, it is subjected to mechanical forces. The direction of this force can be determined by Fleming's left hand rule and its magnitude.
If the first finger is extended, the second finger and the thumb of the left hand will hang down to each other, the first finger indicates the direction of the magnetic field, the next finger indicates the current direction, and the third thumb-like thumb indicates the direction of the force experienced by the magnetic field direction through the conductor, which is displayed as:
F = BIL in Newtons (N)
Where :"B" is the magnetic flux density, "I" is the current, and "L" is the length of the conductor in the magnetic field.
Whenever the power weight winding is supplied to a DC power supply, a current is built up in the winding. The field winding or permanent magnet will provide the sulfonate field. Therefore, based on the above principle, the armature conductor is subject to force due to the magnetic field.
In addition, the commutator is designed with similar parts to obtain one-way torque, otherwise once the conductor's mode of motion is flipped upward within the magnetic field, the path of the force is flipped every time. So, this is how a DC motor works.

V.Type OF DC Motor

5.1 Gear DC Motor

A gear motor tends to reduce the speed of the motor, but torque increases accordingly. This property comes in handy because DC motors can spin too fast for electronics to use. The gear motor usually consists of a DC brush motor and a gear box connected to the shaft.
The motor is distinguished by two connected units. It has many applications due to its design cost, reduced complexity and cost of building applications such as industrial equipment, actuators, medical tools and robots.

5.2 Geared Motor

Gear reduction motors consist of a small gear driving a large gear. There may be several sets of these reduction gears in the reduction gear box.

Sometimes geared motors are used to reduce the rotational shaft speed of the motor in the device being driven, such as in small electronic clocks, where a miniature synchronous motor may turn at 1,200 rpm, but is reduced to 1 rpm to drive the second hand and further shrinks the clock mechanism to drive the minute hand and hour hand. Of course, the size of the driving force does not matter, as long as it is sufficient to overcome the frictional shadow effects of the clock mechanism.

5.3 Series DC motor

In a series DC motor, the field winding is internally connected in series to the armature winding. Series DC motors offer high starting torque, but can never operate without a load and are capable of moving very large shaft loads when first powered on. Series DC motor is also called series wound motor.
In a series DC motor, the field winding is connected to the armature in series. The field strength varies with the change of armature current. At reduced load speed, the series motor produces superior torque. Its starting torque exceeds that of different types of DC motors.
In addition, it can more easily dissipate the heat that accumulates in the winding due to carrying a large amount of current, and its speed varies greatly between full and empty load. When the load is removed the motor speed increases and the current through the armature and excitation coils decreases. It is dangerous to run large machines without load.

The current passing through the armature and the exciting coil is reduced, and the strength of the magnetic flux lines around it is weakened. If the strength of the flux line around the coil decreases at the same rate as the current flowing through the coil
Both will decrease at the same rate as the motor speed increases.

5.4 Shunt Motor

Shunt motors can also be said to be parallel DC motors in which the field windings are shunt or connected in parallel to the armature windings of the motor. Parallel DC motor is widely used because of its best speed regulation performance. In addition, the supply voltage of the armature winding and the excitation winding is the same, however, there are discrete branches of the armature current and the excitation current flow.

Compared with series motor, parallel DC motor has some unique operating characteristics. Since shunt excitation line black is made of thin wire, it cannot generate high current to start as series excitation does. This means that the parallel motor has an extremely low starting torque, which requires a very small shaft load.

When a voltage is applied to a shunt motor, a very small amount of current flows through the shunt coil. The armature of a parallel motor is similar to a series motor in that it absorbs current to create a strong magnetic field, and due to the interaction of the magnetic field around the armature and the magnetic field generated around the shunt field, the motor begins to rotate.
As with a series motor, when the armature begins to turn, a back electromotive force is created. The back electromotive force will cause the current in the armature to start decreasing to a very small level. When the motor reaches full speed, the armature will absorb the current directly related to the size of the load. Since the load is generally smaller, the armature current is smaller.

5.5 Dc Compound Motor

Dc compound motors include a separate shunt field that has excellent starting torque but faces problems in variable speed applications. The magnetic fields in these motors can be connected in series by armatures or by parallel magnetic fields that are individually excited. The series magnetic field provides superior starting torque, while the parallel magnetic field provides enhanced speed regulation. However, series fields can cause control problems in variable speed drive applications and are not usually used for four-quadrant drives.

5.6 Externally Excited DC Automatic Machine

As the name suggests, the field winding or coil is powered by a separate DC power supply. These motors are unique in that the armature current is not provided throughout the field winding because the field winding is reinforced by a separate external DC current source. The torque equation for a DC motor is T0 = Ka a, in which case the torque is changed by changing the field flux and is independent of the "la" armature current.

5.7 Self-excited DC Motor

In this type of motor, the current in the winding can be supplied through the motor or the machine itself. In addition, the motor is divided into series winding and parallel winding motor.

5.8 Permanent Magnet Dc Motor

Permanent magnet DC motor, (PMDC) including armature winding. These motors are designed with permanent magnets, which are placed on the inner edge of the stator core to generate magnetic flux. The rotor, on the other hand, consists of a conventional DC armature, including a brush and a commutator piece
In a permanent magnet DC motor, a magnetic field can be formed by a permanent magnet. Therefore, the input current is not used for excitation, and is used for air conditioning, windshield wipers, car starters, etc.