I. Analysis of Common Relay Problems
When using a relay, please refer to the (relay manufacturer's) instruction manual for common application issues and operational guidelines. Do not exceed the rated voltage or load current. Excessive discharge voltage may cause partial short circuits between the relay coil cores, leading to improper relay operation. It may also cause issues such as incorrect surge protection of the relay's diodes.
Therefore, there are quite a few issues to pay special attention to with relays. Below, we will discuss and analyze some common problems related to relays:
1. Never exceed the rated voltage of the load current during the application of a relay. Excessive voltage may cause a partial short circuit between the relay coil cores and result in poor relay operation. It may also lead to malfunctions such as incorrect surge protection of the relay's diodes.
2. Poor insulation between relay outputs is mainly due to the arcing generated between relay contacts being distorted by external electromagnetic fields or the electromagnetic field generated by the operating coil, reaching the coil terminals and causing a short circuit. However, the carbon or contact powder deposits generated by the arcing between contacts under load are a direct cause of poor insulation, leading to reduced insulation performance or voltage withstand capability.
3. Relays sometimes experience increased loop resistance in power supply circuits. This is mainly due to the damage caused by organic compounds adhering to the surface of the relay contacts. To remove the natural gas emitted from the molded components of the relay beforehand, a baking process (heating under high vacuum) is performed. Molded components that significantly reduce natural gas emissions have also been developed and are gradually being used in various products.
4. Secondly, relays have higher requirements for small and medium-sized, highly sensitive equipment, therefore the coil core wire is becoming increasingly thinner. Because relays are mounted on a printed steel plate, even after cleaning, ultrasonic waves can sometimes concentrate on the coil core wire, causing it to break. The key is that relays generally cannot be cleaned with tap water to remove dust and dirt; otherwise, the use of water will create a strong standing wave, which may cause the coil core wire to break. Therefore, it is essential to determine this beforehand.
5. The current decreases as the coil temperature of the AC-operated relay rises (approximately 0.4% decrease for every 1°C increase). Avoid incorrect diode connections within the relay to prevent misoperation. Otherwise, the relay may vibrate and disconnect, and in severe cases, it could even damage the relay.
II. How to use relays correctly
When using relays, it is essential to follow the instruction manual correctly and ensure that each parameter is within its specified range to guarantee safety. Furthermore, the operating time and load capacity of a relay cannot be guaranteed; they will vary depending on the surrounding environment and the specific load conditions.
When using relays, a rectangular wave should be used if the relay is used indoors. If an AC relay is used indoors, a sine wave should be used. To ensure the relay functions properly, it must not be damaged or subjected to impacts, otherwise its internal components will be damaged.
When using a relay, it's crucial to ensure the ambient temperature is neither too high nor too low, and the humidity is moderate. Furthermore, the air must be free of harmful substances, as these can easily affect the relay's performance. If it's a polarized relay, the voltage characteristics of its coil must be determined to ensure its proper operation.
