Relays are automatic switching components with isolation functions, widely used in remote control, telemetry, and communication. In the previous article, we discussed time relays. To enhance your understanding of relays, this article will introduce safety relays, their functions, and usage. If you are interested in relays, please continue reading.
I. Safety Relay
A safety relay is a combination of several relays and circuits designed to complement each other's abnormalities and defects, achieving a complete relay function with accurate operation and low false alarms. The lower the error and failure rate, the higher the safety factor. Therefore, various safety relays need to be designed to protect different levels of machinery, with the main goal of protecting machinery operators exposed to different levels of hazards.
The so-called "safety relay" is not a "fault-free relay," but rather a relay that performs regular actions when a fault occurs. It has a forced-guided contact structure, which ensures safety even in the event of contact melting, which is completely different from a regular relay. As shown in Figure 1.
A safety relay is an essential control component in a safety circuit. It accepts safety inputs, makes judgments through its internal circuitry, and deterministically outputs a switching signal to the equipment's control circuit. Simply put, safety relays are dual-channel signal types; they can only function properly when both channels are functioning correctly. During operation, if either channel signal is interrupted, the safety relay will stop outputting until both channels are functioning correctly and reset.
II. Function of Safety Relays
A safety relay is a combination of several relays and circuits designed to compensate for each other's abnormalities, achieving a complete relay function with accurate operation and low false alarm rates. The lower the error and failure rate, the higher the safety factor. Therefore, various safety relays need to be designed to protect different levels of machinery, with the primary goal of protecting machinery operators exposed to different levels of hazards. Their main functions are as follows:
1. Expand the control range. For example, when the control signal of a multi-contact relay reaches a certain value, it can simultaneously switch, open, and close multiple circuits according to different forms of contact groups.
2. Amplification. For example, sensitive relays and intermediate relays can control circuits with very small control signals, even those with high power.
3. Integrated Signals. For example, when multiple control signals are input to a multi-winding relay in a specified manner, they are compared and integrated to achieve the intended control effect.
4. Automation, remote control, and monitoring. For example, relays in automatic devices, together with other electrical appliances, can form a program control circuit to achieve automated operation.
III. How to Use Safety Relays
When using safety relays, it is essential to pay attention to the correct operating methods. The key to using safety relays correctly lies in mastering the wiring method of the protection input circuit. Generally, there are three wiring methods for safety relays. After the safety relay is properly connected, it is used to protect mechanical safety and personal safety.
To ensure a safety relay functions correctly, it must be wired using the correct wiring method. One wiring method involves connecting the normally closed contact of the protective element in series with the safety relay's power supply. Then, short-circuit the input circuit of the safety relay itself. This method is relatively simple and convenient.
The second method involves connecting the normally closed contact of the protection element to the single-channel input contact of the safety relay, and then short-circuiting the dual-channel contacts. The third method involves connecting the normally closed contacts of the protection element to the dual-channel input circuit, and short-circuiting the single-channel input circuit.
Using a safety relay is actually not complicated. Once the power supply is connected correctly, it can be used normally in the control input circuit. As a control component that is essential in a safety circuit, the safety relay judges the input through its internal circuit. Most safety relays on the market are dual-channel signal type, so the safety relay can only work properly when both channels of the signal are normal.
If one of the signal channels of the safety relay disconnects during operation, the safety relay will stop outputting until both channels return to normal and are reset. Correct usage of the safety relay depends on proper wiring; correct wiring greatly ensures the safety relay functions correctly.
