Power relay is a key component for controlling the on and off of circuits in power systems. Contact adhesion and coil burning are common failure modes that can lead to equipment failures and even safety accidents. In-depth analysis of these failure causes and targeted preventive measures are essential to ensure the reliable operation of power relays.
Failure causes and mechanisms of contact adhesion. Contact adhesion is mainly caused by the strong arc generated when the contacts break large currents or inductive loads, and the metal on the high-temperature contact surface melts and fuses with each other. In addition, frequent switching causes oxidation and roughness of the contact surface, increases contact resistance, further aggravates heating, and is also prone to cause adhesion. For example, in the car starting circuit, the power relay needs to connect a large current instantly. If the contact material has insufficient arc resistance, arc erosion will quickly destroy the contact surface, leading to adhesion. At the same time, dust and corrosive gases in the environment enter the contact gap, accelerating the chemical corrosion of the contacts, which is also a potential cause of adhesion.
Preventive measures for contact adhesion. In terms of material selection, silver alloy, tungsten alloy and other contact materials with excellent arc resistance are used. These materials have high melting points and good conductivity, which can effectively inhibit arc erosion. For example, silver cadmium oxide (AgCdO) contacts can reduce arc energy and the probability of metal welding by adding cadmium oxide to silver. In terms of structural design, the arc extinguishing chamber structure is optimized, and magnetic blowing, air blowing and other technologies are used to quickly extinguish the arc. For example, the magnetic blowing arc extinguishing device stretches the arc and quickly cools it through the action of the magnetic field, so that it can be extinguished quickly. At the same time, the pressure and contact area of the contacts are reasonably controlled to ensure that the contact is tight and stable, and the contact resistance and heat are reduced.
Analysis of the failure causes of coil burnout. Coil burnout is usually caused by long-term overload operation of the coil, and the current exceeds the rated value, resulting in excessive heating of the coil. In addition, abnormal voltage, such as too high or too low voltage, will also affect the normal operation of the coil. When the voltage is too high, the coil current increases and the heating intensifies; if the voltage is too low, the relay may not be properly attracted, the armature vibrates repeatedly, and the coil continues to work at a high current. In addition, aging and damage of the coil insulation layer will cause short circuit between turns, and the short-circuit current will increase rapidly, causing the coil to burn out. Excessive ambient temperature and poor heat dissipation will also accelerate the aging of the coil insulation layer and increase the risk of burning out.
Effective strategies to prevent coil burning. First, according to the actual working current and voltage, reasonably select the rated parameters of the power relay to ensure that the coil operates within a safe range. At the same time, set overcurrent and overvoltage protection devices in the circuit, such as fuses and circuit breakers, to quickly cut off the circuit and protect the coil when the current or voltage is abnormal. In terms of heat dissipation design, optimize the shell structure of the relay, add heat sinks or use materials with good thermal conductivity to improve heat dissipation efficiency. For relays that work for a long time, intermittent working system can be adopted to avoid long-term continuous power supply of the coil. In addition, regularly check the state of the coil insulation layer, replace aging and damaged coils in time to prevent short circuit between turns.
The impact of manufacturing process on failure prevention. In the production process of power relay, strict control of manufacturing process is the key to preventing failure. The processing accuracy of the contact directly affects the contact performance. High-precision stamping and welding processes can ensure that the contact surface is flat and the contact is tight. When winding the coil, uniform winding technology is used to ensure accurate coil turns and good interlayer insulation. At the same time, strict quality inspections are carried out on the finished products, including contact resistance test, coil insulation resistance test, temperature rise test, etc., and unqualified products are screened by simulating actual working conditions to reduce the probability of failure from the source.
Maintenance and management measures. During use, the power relay is regularly maintained, the dust and oxide layer on the contact surface are cleaned, the contact wear is checked, and the contacts with severe wear are replaced in time. Monitor the working temperature and current of the coil, and find out the cause in time if abnormalities are found. Establish a use file of the relay, record its working time, fault conditions and other information, and provide a basis for preventive maintenance. In addition, operators need to use the relay strictly in accordance with the operating procedures to avoid overload or short circuit due to misoperation.
Application prospects of new technologies and new materials. With the development of science and technology, new materials and technologies provide new directions for the failure prevention of power relays. For example, the application of nanomaterials can improve the arc resistance and wear resistance of contacts; intelligent monitoring technology detects the contact status and coil temperature in real time through built-in sensors to achieve fault warning. Using solid-state relays to replace traditional electromagnetic relays can avoid contact wear and arc problems and improve reliability. In the future, as these new technologies and new materials continue to mature and be applied, the failure problem of power relays will be more effectively solved.
