Coil Input Precautions
1. Rated voltage ensures relay reliability. While the relay can still operate if the coil voltage exceeds the operating voltage, it may malfunction under strong impacts. Exceeding the maximum operating voltage can cause coil insulation degradation, inter-turn short circuits, and burnout.
2. The relay coil resistance changes by approximately 0.4% °C due to ambient temperature variations and the relay's own heating. Therefore, increased coil temperature will raise both the operating and breaking voltages.
3. Automotive relays are battery-powered. High loads can cause a drop in power supply voltage, affecting relay lifespan. Pay attention to the impact of power supply voltage fluctuations on relay reliability.
4. Maximum Continuous Coil Voltage: Besides relay stability, the maximum continuous coil voltage is primarily limited by the insulation performance of the enameled wire. The insulation class of the enameled wire should be understood. In practical use, for Class F insulation at an ambient temperature of 40 °C, the temperature rise can be limited to a maximum of 115 °C as measured by the resistance method. However, due to the non-uniformity between the inner and outer coils, a value of 105 °C is recommended.
5. Coil Electrolytic Corrosion: Automotive relays operate in environments with fluctuating temperatures and humidity for extended periods. When the coil is continuously connected to the positive terminal of the power supply (with the negative terminal disconnected), electrolytic corrosion can occur, leading to wire breakage. Therefore, the relay coil should not be connected to a high potential; the relay coil and moving reed must be disconnected from the positive terminal of the power supply.
Contact Usage Precautions: The contacts are the most critical components of a relay. Their reliability is affected by the contact material, contact voltage and current (especially the switching voltage and current waveforms), load type, switching ratio, and environmental conditions. Contact Voltage: Inductive loads generate very high reverse voltages. Higher voltages result in greater energy, accelerating contact electrolytic corrosion and metal transfer. Caution should be exercised. Contact Current: The current during contact closure and opening significantly impacts the contact. When the load is a motor or headlight, the inrush current during closure is large, leading to greater contact wear and metal transfer. Contact transfer can cause contact adhesion failure; verification testing should be performed.
Contact Protection Reverse Voltage: When disconnecting a relay coil series circuit or inductive loads such as motors and electromagnets, surge absorption using diodes or similar devices must be employed to protect the contacts. Disconnecting an inductive load generates a reverse voltage of hundreds to thousands of volts, exacerbating contact corrosion and reducing contact lifespan. Furthermore, when the inductive load current is less than 1A, the arc generated by the reverse voltage decomposes the organic gases volatilized from the relay's internal coil and plastic, forming black oxides and carbon deposits on the contacts, leading to poor contact. Contact Metal Transfer: Contact metal transfer is the unidirectional transfer of contact material under DC current. With increasing switching frequency, pits form on the anode contacts and bulges on the cathode contacts. These bulges and pits can easily cause mechanical locking, leading to contact adhesion. Anti-transfer contact materials or protective circuits should be selected. Contact Protection Absorption Circuit: Using contact protection components or circuits can reduce reverse voltage, but improper use can have negative effects.
Relay Usage Precautions
1. To prevent contamination of the lead surfaces, do not directly contact the leads; otherwise, solderability may decrease.
2. The lead positions should align with the holes on the printed circuit board. Any improper fit may cause dangerous stress on the relay, damaging its performance and reliability. Please refer to the drilling diagram in the sample for drilling.
3. After inserting the relay into the circuit board, do not bend the leads to avoid affecting the relay's sealing or other performance characteristics.
4. Do not apply excessive pressure to the relay housing during insertion to avoid housing breakage or changes in operating characteristics.
5. The insertion and removal force for the quick-connect pins is 10 kgf. Excessive insertion and removal force will damage the relay; insufficient pressure will affect contact reliability and current carrying capacity.
6. It is particularly important to emphasize that if the relay is accidentally dropped or impacted during installation, although the electrical parameters may be within acceptable limits, its mechanical parameters may change significantly, posing a serious hazard. Such relays should be avoided if possible.
7. Do not use silicone-containing resins and preservatives, as they can cause contact failure, even in molded relays.
8. Ensure the coil and contact power supplies are connected according to the specified polarity. Generally, the moving spring is connected to the positive (+) terminal.
9. Avoid applying voltage to the coil exceeding the maximum permissible voltage or causing the coil temperature rise to exceed the insulation class of the enameled wire.
10. Rated load and lifespan are under specified standard conditions and cannot cover all the usage requirements of automotive relays. Actual contact load and lifespan can vary significantly due to load type, environmental conditions, operating frequency, and other factors.
