Latching relays are ideal for low-power or high-temperature applications where continuous coil voltage isn’t feasible. They operate using short voltage pulses to change and maintain their contact position, even after power is removed (“SET” to activate, and another pulse to reset).
Magnetically held relays, a type of latching relay, use electromagnetic fields to maintain their state without constant power, offering high energy efficiency. They are reliable, resistant to faults, and less prone to external disruptions, making them ideal for long-term state maintenance. Additionally, their reduced mechanical movement ensures a longer operational lifespan compared to traditional relays.
We may encounter problems with relays not working correctly in various situations, such as the following examples:
Coil Failures
Relay coil failures are common in the following situations:
External causes (overvoltage, ultrasonic cleaning, etc.) cause the relay coil to break and trigger a failure;
Insufficient power supply to the coil can also cause the relay to fail if the voltage supplied to the coil is lower than the operating voltage;
Built-in diode type relays can also cause the contacts not to operate if the polarity of the coil is reversed;
In addition, if the coil is energised for a long period of time, the coil part will be in a high temperature state, which will lead to the destruction of the coil.
Solution: You should confirm in advance that the coil voltage is in accordance with the voltage supplied in the application environment, and ensure that the correct polarity is connected. During use, avoid energising the relay coil for a long period of time if it is not necessary.
Contact sticking
Overcurrent connection, switching frequency exceeding the rated switching frequency of the relay and abnormal vibration of the contact area may cause the contacts to stick then make the relay fail..
Solutions: In order to avoid contact sticking while ensuring the quality of the relay, consider selecting a relay with large contact capacity and high switching frequency when choosing a relay. It is safer to choose solid state relays.
Poor contact
Corrosion or damage to the contact surface, unstable coil voltage, foreign matter such as dust attached to the contact surface, or severe vibration in the environment where the relay is used may all lead to poor contact.
Solutions: Consider replacing the stable power supply according to different reasons, or choose the relay with good dustproof, sealing or higher anti-vibration ability, and also consider the impact of the arc, choose the relay products with arc extinguishing device;
Indicator light does not light up
When the coil power supply is insufficient, coil DC power supply or polarity reversal may cause the relay display lamp malfunction.
Solutions: First of all, we should judge which cause the display light malfunction. Insufficient power supply to the coil will cause the whole relay to be inoperative. While DC power supply to the coil and reverse polarity will cause the relay contacts to operate but the indicator light will not light up. According to different situations, choose to replace the relay or change the two poles wiring.
When facing the problems in using relay, first you need to calm down and try to find out the problems on it. I will tell you some common testing method and inspection tips when find out the problems.
Use a Multimeter
First tips when you can’t find out the problem is using the multimeter. Multimeter is a tool that's often used to measure the relay's resistance and contact state. Just remember to disconnect power before you get started to keep things safe and sound.
Use an Oscilloscope
Using an oscilloscope is an effective way to analyze the performance of a relay in detail. This tool allows you to monitor the relay’s switching time, providing precise information on how quickly the relay responds to input signals.
Try Replacing the Relay
Carefully remove the faulty relay, ensuring that the process does not damage the surrounding components or wiring. After the replacement, conduct a thorough test of the associated equipment to confirm that the issue has been resolved. This step verifies the effectiveness of the replacement and ensures the system is functioning correctly without any lingering problems. Regular maintenance and inspection can help prevent similar issues in the future.
Testing a relay is a straightforward process that can help identify any faults in its operation.
Begin by disconnecting the relay from the circuit to ensure accurate testing without interference from other components. Use a multimeter to check the resistance across the coil terminals; a reading within the specified range indicates a functioning coil.
Next, test the relay contacts by applying the rated voltage to the coil and measuring continuity across the normally open (NO) and normally closed (NC) contacts. The NO contacts should close, and the NC contacts should open when the coil is energized. If the relay fails any of these steps, it may need to be replaced.
Testing and inspecting relays are crucial for maintaining the proper functioning of electronic and electrical systems. Simple techniques like visual observation, electrical measurements, and listening for the relay’s operational clicks can help you quickly evaluate its condition. These straightforward methods allow for prompt identification of issues, enabling timely corrective actions to ensure reliable system performance.
