Introduction:
Relays are a common and important component in the field of electrical engineering, which acts like an electromagnetic switch, and is able to control large currents through small currents. In this article, Mr. Ye will be the working principle of the relay, including electromagnetic induction, classification structure, etc., and introduce how to effectively detect the working state of the relay.
First, how it works:
The basic working principle of relays involves the application of electromagnetic induction, which controls the state of the contacts through the formation and disappearance of electromagnetic fields, and realizes the conduction and disconnection of circuits.
1.1 Electromagnetic Induction:
The core part of the relay is the coil, and when the coil is energized, a strong magnetic field is generated. This magnetic field is generated when flowing in a current** circle, and according to Ampere's loop law, the magnetic field formed is concentrated in the core.
1.2 Coil:
The coil is generally made of insulated wrapped copper wire and is located inside the relay. When the coil is energized, an electric current flows through the copper wire, creating an electromagnetic field.
1.3 Iron Core:
The role of the iron core is to enhance and concentrate the magnetic field. The core is usually made of soft iron, which conducts magnetism more efficiently. Through electromagnetic induction, the magnetic field generated by the coil magnetizes the iron core, forming a strong magnetic state, and this magnetic state affects the state of the contact.
1.4 Contacts:
Inside the relay there are one or more contacts, which are located near the iron core. Contacts are usually made of conductive materials, such as silver alloys. The state of the contacts depends on the influence of the magnetic field.
1.4.1 NO Contact:When the relay is not energized, the contacts are closed. After being energized, due to the influence of the magnetic field, the contacts open and the circuit is turned on.
1.4.2 NC Contacts:When the relay is not energized, the contacts are open. When energized, the action of the magnetic field causes the contacts to close, cutting off the circuit.
Second, the classification of relays
Relays are divided into various types according to their different working modes and application scenarios, mainly including normally open relays, normally closed relays and hybrid relays. At the same time, the internal structure of the relay includes coils, contacts, cores, etc., and the design of each component has an important impact on the performance of the relay.
Classification of relays
2.1 Normally open relay (NO, normally open relay):When the relay is not energized, the contacts are closed and the circuit is disconnected. After being energized, due to the action of the magnetic field generated by the coil, the contacts open and the circuit is unobstructed. Normally open relays are widely used in scenarios where the circuit needs to be shut down when the control signal arrives.
2.2 Normally Closed Relay (NC):When the relay is not energized, the contacts are open and the circuit is unobstructed. After power-on, the contacts close and the circuit opens due to the influence of the magnetic field. Normally closed relays are often used when a circuit needs to be turned on when a control signal arrives.
2.3 Hybrid Relays:This relay combines normally open and normally closed characteristics and has two sets of contacts at the same time. One group closes when not energized and the other disconnects when unenergized. Hybrid relays can be more flexibly adapted to different application needs.
Third, the application of relays:
As an important electrical component of electronic appliances, relays have a wide range of applications in various fields, and their reliability and flexibility make them ideal for control and protection of a variety of circuits. The following are the specific applications of relays in different fields.
3.1 Automotive electrical system
Relays play a key role in automobiles, controlling and protecting a wide range of electrical devices. Here are some common relay applications in automotive electrical systems:
3.1.1 Starting Relay:Control the starting circuit of the engine to ensure that the engine starts properly.
3.1.2 Power Relay:Manage the distribution of power in the vehicle's electrical system and ensure that individual appliances receive the proper power supply**.
3.1.3 Horn Relay:It is used to activate the car horn and provide an audible warning signal.
3.1.4 Wiper Relay:Control the movement of the wipers and automatically adjust the frequency of wipers according to the amount of rain.
3.1.5 Fog Light Relay:Controls the switch of the fog lights to provide additional illumination.
3.2 Household appliances.
In the home environment, relays are used to control and protect various household appliances, improving their performance and safety. Some common applications include:
3.2.1 Air Conditioner Relay:Control the start-stop and temperature regulation of the air conditioner.
3.2.2 Refrigerator Compressor Relay:It is used to start and stop the refrigerator compressor to ensure stable refrigeration effect.
3.2.3 Washing Machine Relay:Manage the various functions of the washing machine, such as water intake, drainage, stirring, etc.
3.2.4 Oven Relay:Control the heating element of the oven to ensure precise temperature control.
3.3 Automated systems
In industry and automation, relays are the basic elements in automatic control systems and are used to perform complex control tasks. Some of the applications in automation systems include:
3.3.1 PLC (Programmable Logic Controller) Relay:It is used to perform various logic control tasks in industrial automation systems.
3.3.1 Motor Control Relay:It is used to start, stop and control the motor, and protect the motor from overload and short circuit.
3.3.2 Temperature Control Relay:Monitor and control temperatures in industrial processes to ensure safe operating ranges.
3.4 Other areas
Relays also play a key role in many other areas, such as:
3.4.1 Communication System:It is used for the switching and control of telecommunication equipment.
3.4.2 Medical Equipment:Circuits used to control medical devices and ensure their safe and reliable operation.
3.4.3 Energy Management System:It is used to control various electrical equipment in the energy distribution and management system.
Wait a minute. Fourth, the detection method
The proper operation of relays is critical to the stability of the electrical system. To ensure the reliability of the relay, regular testing is necessary. The following explains how to detect the working state of the relay, including the method of measuring the resistance of the coil and the conduction of the contact. Steps and considerations are provided so that readers can get hands-on.
4.1 Measure the resistance of the coil:
The coil is the core part of the relay, and the measurement of its resistance value can help determine whether the coil is normal. Here are the steps to measure the resistance of the coil:
4.1.Step 1:
Set the measuring range of the multimeter to the appropriate resistance range, usually choosing a larger range to avoid damaging the gauge pen.
Connect the pen to the two terminals of the relay coil separately.
Read the resistance values displayed in the table.
4.1.2 Precautions:
The normal coil resistance should be within the range specified in the relay specification sheet. If the resistance value is outside the normal range, it may indicate that the coil is faulty and the relay needs to be serviced or replaced.
Some relays may have two sets of coils, and depending on the relay model and specifications, the resistance of the two sets of coils needs to be measured separately.
4.2 Contact Continuity Detection:
The conduction of the contacts directly affects the connection status of the relay in the circuit. Here are the steps to check the contact turn-on:
4.2.Step 1:
Set the measurement range of the multimeter to the resistance range and select the appropriate range.
Connect the stylus to the relay contacts separately. Depending on the type of relay, there may be multiple sets of contacts that need to be tested separately.
Read the resistance values displayed in the table.
4.2.2 Precautions:
For normally open contacts, the resistance value should be infinity (open circuit state) under normal conditions;For normally closed contacts, the resistance value should be close to zero (closed).
If the contact conduction is not as expected, it is possible that the contact is sticky or damaged, and the contact section needs to be further inspected.
4.3 Power-on detection:
By loading the relay coil with a working voltage and detecting the change of the contact state, the reliability of the relay in actual operation can be judged. Here are the steps for power-on detection:
4.3.Step 1:
Use a DC power supply or battery to provide the appropriate voltage and connect to the relay coil.
By observing changes in the state of the contacts, it is possible to determine whether the contacts are closed or disconnected by auditory or optical methods.
4.3.2 Precautions:
Please ensure that the voltage provided meets the relay specifications to prevent damage to the relay.
When performing a power-on test, pay attention to whether the relay is working properly to ensure that the contact behavior is as expected.
5. Common problems and solutions
Relays, as an important part of the electrical system, encounter some common faults. The following is a list of common problems and corresponding solutions to help readers better cope with the actual situation.
5.1 Problem: The coil burns out
5.1.1 Possible Causes:
Overload current. The coil is overheating.
5.1.2 Workaround:
Make sure the supply voltage meets the relay specifications.
Check whether the load of the relay is out of the specified range.
Consider using additional overload protection.
Check the coil for short circuits or ground faults.
Regularly clean the dust and debris around the relay and maintain ventilation.
5.2 Problem: Contacts are stuck or welded
5.2.1 Possible Causes:
Prolonged use leads to wear of the contacts.
There is no proper overload protection.
5.2.2 Workaround:
Replace contacts regularly and develop a maintenance schedule based on frequency of use and load.
Use appropriate overload protection devices to prevent contacts from sticking due to excessive current.
5.3 Problem: Loose or damaged contacts
5.3.1 Possible Causes:
Shock or shock.
Prolonged use leads to fatigue.
5.3.2 Workaround:
Make sure the relay is securely installed to prevent external vibration and shock.
Regularly inspect and tighten the contacts to avoid loosening.
According to the service life of the relay, replace the aging contacts in time.
5.4 Problem: Worn contacts cause resistance to rise
5.4.1 Possible Causes:
Wear and tear caused by prolonged use.
Relays switch on and off frequently.
5.4.2 Workaround:
Check the status of the contacts regularly and replace the contacts that are heavily worn in time.
Reduce the number of frequent switching of relays.
Use relays with less load.
5.5 Problem: Relays do not engage or release
5.5.1 Possible Causes:
Faulty coils. Spring failure.
5.5.2 Workaround:
Check the resistance of the coil to make sure it is within the specified range.
Check that the springs are installed correctly and that they are not deformed or damaged.
If there is a problem with the coil or spring, replace it in time.
5.6 Problem: Bow vibration or sparks occur at the contacts
5.6.1 Possible Causes:
The load current that needs to be interrupted is too large.
Interrupt high voltage.
5.6.2 Workaround:
Consider using relays that are specifically designed for high loads.
Capacitors are connected in parallel at both ends of the relay to reduce sparks during breaking.
Reduce the load current or voltage and select the appropriate relay model.
VI. Conclusion:
As a key component in electrical control, relays play an irreplaceable role in modern engineering. With a deep understanding of how it works and how to detect it, we are better able to deal with the problems that may be encountered in various electrical systems.