Armature: The core component of the motor

Armature: The core component of the motor
Post Date:2024-10-28,
Armature
The armature is a key component in the motor or generator. It is responsible for converting electrical energy into mechanical energy, or converting mechanical energy into electrical energy. The armature is widely used in DC motors, synchronous motors and asynchronous motors. Although its structure and working principle are different in different motor types, it always plays a core role in the conversion of electrical energy and mechanical energy. This article will introduce the structure, classification, working principle and application field of the armature in detail.

Definition and function of armature


The armature refers to the rotating part in DC motors and AC synchronous motors, usually composed of winding coils, iron cores and commutators. The main function of the armature is to generate or induce electromagnetic fields, thereby realizing the conversion between mechanical energy and electrical energy.

  • In the motor: the armature is the rotating part, and the magnetic field generated by the current interacts with the stator magnetic field to generate torque and drive the motor to rotate.


  • In the generator: the armature cuts the magnetic lines of force by rotation, generates induced electromotive force, and outputs electrical energy.

Armature structure


The armature usually consists of the following parts:

Armature core:


The armature core is the core of the armature, which is used to support the armature winding and enhance the electromagnetic induction effect. The core is usually made of silicon steel sheets stacked together to reduce iron losses (such as eddy current loss and hysteresis loss) and improve motor efficiency. The surface of the silicon steel sheet is coated with insulating material to prevent short circuits between the sheets.

Armature winding:


The armature winding is a coil made of conductive material (usually copper or aluminum) wound on the armature core. The function of the armature winding is to induce current under the action of the electromagnetic field, or to interact with the magnetic field in the motor to generate torque. In DC motors, the winding is usually arranged as a closed loop to allow current to flow.

Commutator (DC motor only):


In DC motors, the armature works with the commutator. The commutator is a ring-shaped structure composed of multiple copper sheets that contacts the external circuit through brushes. The function of the commutator is to reverse the direction of the current periodically to ensure that the motor rotates in the same direction.

Brush:


A brush is a device used to transfer electric current, usually made of carbon or metal. In a DC motor, the brush contacts the commutator and provides current through the armature winding. In an AC motor, the brush is used to transfer current to the armature.

Classification of armatures

According to different motor types, armatures can be divided into the following categories:

DC motor armature:


The armature of a DC motor is connected to the power supply through the commutator, and the winding cuts the magnetic lines of force through the magnetic field, thereby generating current or torque. The DC motor armature is usually mounted on the rotor, and an induced current is generated as the motor rotates.


AC motor armature:


In synchronous and asynchronous motors, the armature can be located on the stator or rotor. In a synchronous motor, the armature is usually located on the stator, and the rotor is the magnetic pole. In an asynchronous motor (such as an induction motor), the armature is located on the rotor, and the stator generates a rotating magnetic field, which generates current on the rotor through electromagnetic induction.

Generator armature:


In a generator, the armature is responsible for converting mechanical energy into electrical energy. The armature structure of a DC generator is similar to that of a DC motor. The armature is rotated by an external mechanical drive to generate current. The armature of an AC generator is usually located on the stator and induces voltage through the rotating magnetic field.

How the armature works in an electric motor


The main task of an electric motor is to convert electrical energy into mechanical energy, and the armature plays a central role in this process.

1.Current flows through the armature winding


When an external power source supplies power to the motor, current flows through the armature winding. The armature winding is usually a set of coils mounted on the rotor, which pass through a fixed magnetic field or electromagnetic field in the stator.

2.Generation of electromagnetic force (Ampere's law)


According to Ampere's law, when current passes through a conductor, an electromagnetic force perpendicular to the magnetic field is generated when the current direction is not parallel to the magnetic field direction. Since the armature coil is in the magnetic field of the stator, an electromagnetic force is induced on each winding.

3.Generation of torque


The electromagnetic force on the armature winding generates a torque, which causes the armature (rotor) to rotate. This torque is the result of multiple armature windings acting simultaneously. The rotation of the armature drives the motor shaft to rotate, thereby converting electrical energy into mechanical energy.

4.The role of the commutator (DC motor)


In a DC motor, the armature works with the commutator. The role of the commutator is to change the direction of the current regularly to ensure that the direction of the torque of the armature remains consistent during rotation, ensuring continuous and stable rotation of the motor. Without a commutator, the armature will cause the motor to reverse or stop due to the change in torque induced by the winding.

How the armature works in a generator


The role of the generator is to convert mechanical energy into electrical energy, and the armature is the main source of electrical energy in this process.

1.Armature winding cuts magnetic lines of force


The armature of the generator (usually located on the stator or rotor) rotates under the drive of an external mechanical force. When the armature winding moves in the magnetic field of the stator, the armature coil cuts the magnetic lines of force.

2.Electromagnetic induction (Faraday's law of electromagnetic induction)


According to Faraday's law of electromagnetic induction, when a conductor cuts magnetic lines of force, an induced electromotive force will be generated in the conductor, and the magnitude of the electromotive force is proportional to the strength of the magnetic field, the speed of the conductor and the length of the conductor. When the armature winding rotates in the magnetic field, an electromotive force will be induced in the winding, which is the source of the generator's electrical energy.

3.Generation of induced current


The induced electromotive force generates an induced current in the armature winding. This current can be output through an external circuit for power supply or storage. In a DC generator, the armature maintains the consistency of the current direction through a commutator, while in an AC generator, the current generated by the armature is an alternating current.

Detailed explanation of the electromagnetic induction process of the armature


Whether in a motor or a generator, the working principle of the armature is based on the principle of electromagnetic induction. When explaining in detail, Faraday's law and Ampere's law are usually used:

Faraday's law of electromagnetic induction


Faraday's law shows that when a conductor (such as an armature winding) moves in a magnetic field, an electromotive force is induced. The formula is:

Faraday's law of electromagnetic induction

Wherein, Φ is the magnetic flux, which indicates the number of magnetic lines of force of the magnetic field passing through the armature winding, and t is the time. The armature changes the magnetic flux by rotating, inducing an electromotive force.

Ampere's law (torque principle in motors)


When current passes through the armature wire, according to Ampere's law, the conductor is acted upon by the magnetic field, generating a torque, and the formula is:

Ampere's law (torque principle in motors)


Wherein, F is the force, B is the magnetic field strength, I is the current in the wire, and L is the length of the conductor. This force causes the armature winding to rotate, driving the motor to rotate.

Application fields of armature


The armature is widely used in the following fields:

Motor


The armature is the core component of the motor and is widely used in various types of motors such as DC motors, synchronous motors, and asynchronous motors. In automobiles, industrial production, household appliances and other equipment, armature-driven motors play an important role.

Generator


The generator is a device that converts mechanical energy into electrical energy. In this process, the armature generates an electromotive force through electromagnetic induction and finally outputs current. Generators are widely used in power systems, wind power generation, hydropower generation, and backup power supplies.

Electromagnetic brakes and clutches


In electromagnetic brakes and clutches, the armature achieves braking or power transmission through electromagnetic action. In mechanical equipment, the armature controls the moving parts by controlling the on and off of the current.

Losses and effects of armatures


Copper loss


Copper loss refers to the energy loss caused by the resistance of the wire when the current in the armature winding passes through the wire. Copper loss is usually proportional to the square of the current, so copper loss is more significant under high current conditions.

Iron loss


Iron loss includes hysteresis loss and eddy current loss, which mainly occurs in the armature core. Hysteresis loss is the loss caused by repeated magnetization reversal of the core material during magnetization, while eddy current loss is caused by the induced current in the core flowing inside the core.


Mechanical loss


Mechanical loss is mainly caused by friction and wind resistance during the rotation of the armature. These losses reduce the efficiency of the motor or generator and increase operating costs.

Troubleshooting for armature


During use, if you encounter armature failure, you can use the following methods to troubleshoot and solve it:

The motor does not rotate or the speed is low:

Reason: winding open circuit, poor commutator contact, carbon brush wear, bearing damage, etc.

Solution:


  • Check whether the winding is open circuit or short circuit, repair or replace the winding.


  • Check the contact between the commutator and the carbon brush, clean or replace the severely worn parts.


  • Check whether the bearing is damaged, and replace new bearings if necessary.

Motor overheating:


Reason: winding short circuit, poor ventilation, excessive load, etc.

Solution:


  • Check whether the winding is short circuit, repair or replace the winding.


  • Clean the dust inside the motor and ensure good ventilation.


  • Check whether the load exceeds the rated value and reduce the load appropriately.

The motor is noisy:


Reason: bearing damage, winding looseness, commutator wear, etc.

Solution:


  • Check whether the bearing is damaged, and replace new bearings if necessary.


  • Check whether the winding is loose, re-fix or replace the winding.


  • Check the wear of the commutator, clean or replace the seriously worn parts.

Motor vibrates loudly:


Reasons: bearing damage, rotor imbalance, improper installation, etc.


Solutions:


  • Check the bearing for damage, and replace new bearings if necessary.


  • Check the rotor for balance, and rebalance the rotor.


  • Check the installation of the motor to ensure firmness and stability.

About armature maintenance and care


In order to ensure the long-term and reliable operation of the armature, it is recommended to perform the following maintenance and care regularly:

Cleaning:


Clean the dust and dirt on the surface of the armature regularly to prevent dust accumulation from affecting the heat dissipation performance.


Wipe gently with a clean cloth or soft brush, and avoid using corrosive cleaning agents.

Check the winding:


Check whether the winding is burnt, broken or damaged in insulation.


Use a megohmmeter to measure the insulation resistance of the winding to ensure that it is within the normal range.

Check the commutator:


Check whether the commutator copper sheet is worn, dented or oxidized.


Clean the commutator surface to ensure good contact.

Lubrication:


For armatures with bearings, apply an appropriate amount of grease regularly to reduce friction and wear.

Check the carbon brushes:


Check the wear of the carbon brushes and ensure that their length is within the allowable range.


Replace the severely worn carbon brushes and adjust the pressure of the carbon brushes to ensure good contact.

Conclusion

As a key component of motors and generators, the performance of the armature has a direct impact on the efficiency, reliability and life of the equipment. By understanding the structure, working principle and loss mechanism of the armature, we can better design, use and maintain motors and generators.


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FAQ:

What is an armature and what does it do?

The armature is a core component in motors and generators, used to convert electrical energy into mechanical energy in motors and mechanical energy into electrical energy in generators. The armature coil winding rotates in a magnetic field, generating current or torque through electromagnetic induction.

What is the difference between an armature and a rotor?

In a DC motor, the armature is usually the rotating part (rotor), but in an AC motor, the armature may be the fixed part (stator), mainly depending on the design of the motor. The armature is the part that generates electromotive force and current, while the rotor or stator is just its physical location.

How does an armature work?

The armature rotates in a magnetic field, and electromagnetic induction generates current. In a generator, mechanical energy drives the armature to rotate and generate electromotive force, while in a motor, the armature coil is subjected to force in the magnetic field through the energized armature coil, generating torque to drive the rotor to rotate.

What materials does the armature consist of?

The armature usually consists of an iron core made of soft iron or silicon steel laminations, conductive copper wire windings, and a commutator (for DC motors). The iron core helps to concentrate the magnetic field, while the copper wire windings are responsible for conducting electricity and generating electromotive force.

What is the difference between the role of the armature in DC motors and AC motors?


In DC motors, the armature is the rotating part that commutates the current through the commutator and brushes. In AC motors, the armature is usually the stator, which is used to generate a rotating magnetic field and interacts with the rotor through inductive coupling.

What are the common manifestations of armature failure?


Common armature failures include short circuits, open circuits, or excessive brush wear. These failures usually cause the motor to overheat, vibrate, reduce efficiency, or fail to start.

How to check if the armature is damaged?


You can determine whether the armature is damaged by measuring the winding resistance with a multimeter, testing the winding insulation with a megohmmeter, or checking the contact between the commutator and the brushes. In addition, excessive sparking may also indicate that the armature is faulty.

How does the armature work with the commutator in the motor?


In DC motors, the windings of the armature are connected to the commutator, which changes the direction of the current as the armature rotates to ensure that the motor produces continuous rotation torque.

How to maintain and service the armature?


When maintaining the armature, you should regularly check the contact between the brush and the commutator, clean the commutator surface to reduce sparks, check the insulation and resistance of the windings, and ensure that the armature runs smoothly without abnormalities.

What impact does the armature have on the performance of the motor?


The design and performance of the armature directly affect the power, efficiency, speed and torque output of the motor. The number of turns of the armature winding, the thickness of the wire and the quality of the material will affect the performance of the motor.

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