In general, mechanical relays are used in many electronic devices when high current control is required. These relays switch the flow of current by opening and closing physical contacts. Despite their advantages of reliability and low cost, there are still some drawbacks that cannot be ignored. Following are five major disadvantages that mechanical relay switches have, and further in this article, some key factors that come into play in selecting and using the devices are discussed.
Understand the structure of mechanical relays
Electromagnet: This is the most crucial part of relays. Whenever current passes through electromagnetic coils, it forms a magnetic field. When the relay coil is energized, a magnetic field is formed that attracts the iron core.
Iron core: It is usually made of a soft magnetic material. Its purpose is to displace due to electromagnetic attraction. The iron core moves by controlling the opening and closing of the switch.
Contact: Relay contacts are those parts that connect or disconnect circuits. The normally open, normally closed, and switching contacts are included in the contact. When the electromagnet attracts the iron core, the contacts change to either connect or disconnect the circuit.
Spring: It acts to return the iron core in a no-power condition to its normally open state in the electromagnet, thus restoring the relay back to its initial position. The restoring force provided by this would disconnect or connect the contacts.
Due to certain losses during long-term use, the service life of each structural component is also limited. Next, we will explore the shortcomings of mechanical relays from five aspects and propose corresponding countermeasures.
Life problems caused by mechanical wear and tear
The core working principle of mechanical relays is to control the current through physical contact and disconnection of metal contacts. However, as the usage time increases, the contacts will wear out due to repeated physical contact. This kind of wear can lead to poor contact and increased impedance of the relay switch, and even ultimately result in relay failure.
influence
Poor life: The service life of mechanical relays is relatively short, generally only a few thousand to tens of thousands of times of switching. If some miscellaneous relays are used, their service life will be shorter and there will be no guarantee.
Frequent replacement is required: Due to the short service life of relays, it may be necessary to regularly inspect and replace mechanical relays to ensure the stability and safety of the equipment.
Response strategy
If the application scenario requires frequent switching, solid-state relays or more durable mechanical relay models can be considered. Alternatively, you can choose an excellent relay supplier, QIANJI, which provides long-lasting and high-quality mechanical relays as well as new solid-state relays
Slow Response Speed
The switches are turned on and off by mechanical motion. This makes the response speed of the relay relatively slow. For applications that demand quick responses, such as automation control systems and high-speed circuits, the response time of the mechanical relay may not suffice.
influence
Slow Switching Speed: Generally, the action time of the relay is usually delayed, which may cause a lag in the response of the entire system.
Not suitable for high-speed operations: Generally, mechanical relays are unsuitable in high-speed operating equipment that needs quick switching.
Response strategy
When there is a need to apply high-speed control logic, solid-state relays or any other electronic switching devices shall be selected, responding quicker.
Generate electric arc
When the contacts of a mechanical relay open or close, the current will cause arcing between the contacts. This type of arc may damage the contact surface, further accelerate the aging of the relay, and even pose a risk of fire or electrical accidents.
influence
Arc damage: An arc can cause the melting or contamination of relay contacts, resulting in a decrease in the performance of the relay.
Safety hazards: Electric arcs may also cause fires or electrical failures, affecting the safety of the system.
Response strategy
When designing circuits, arc suppression techniques can be considered, such as adding capacitors or resistors next to the contacts, or selecting relays with better arc dissipation performance.
Mechanical noise
Mechanical relays produce noticeable noise during operation, especially when switching at high frequencies. This type of noise may have an impact on the stability and user experience of the device, especially in noise sensitive applications such as medical equipment or high-precision control systems.
influence
Noise interference: The "click" sound of relays during switching may affect the normal operation of equipment or the comfort of the environment.
Impact on user experience: For some applications that require silence, mechanical relays may not be the best choice.
Response strategy
For applications that require low noise, silent relays or solid-state relays can be considered, as these devices have no physical moving parts and therefore no noise.
Easy to be influenced by environmental factors
The performance of mechanical relay switches may be affected by environmental factors such as temperature, humidity, and dust. High temperature or humid environments may cause corrosion or freezing of relay contacts, thereby affecting their reliability and stability.
Influence
Temperature variation: High temperatures can melt or damage the relay contacts and low temperatures may result in malfunctioning relays.
Humidity: Due to moisture, the relay contact points can corrode and fail in the circuit.
Dust: Since dust and other impurities can enter the interior of a relay and cause malfunction, leading to short-circuiting or other fault conditions.
Strategy
Protective designs shall be selected which, for the mechanical relays are suitable for wider ranges of environment or place the relay in a sealed enclosure to exclude interference from environmental factors.
Summary
Although mechanical relay switches are widely used in many fields due to their simplicity, reliability, and low cost, their drawbacks also need to be given sufficient attention. From mechanical wear and arcing issues to response speed and noise generation, these problems may affect the long-term stability and performance of relays.
When choosing to use mechanical relays, make sure they are suitable for your application needs and consider other alternative solutions, such as solid-state relays, which may be more appropriate. But the price of solid-state relays will be more expensive than mechanical relays. If you need relay requirements, you can contact us. We are a professional relay supplier that can customize your needs for mechanical relays or solid-state relays, and provide affordable prices
