Introduction
Safety relays play an important role in modern automation systems. They are designed to protect the safety of personnel and equipment. Compared with ordinary relays, safety relays have more advanced functions and technologies, can detect faults and provide double safety protection. This article will introduce the basic concepts of safety relays, including their working principles, characteristics and application areas.
1. Basic knowledge of relays
A relay is an electromechanical switching device that uses electrical energy to operate its mechanical contacts, separating two circuits and acting as a contact between them. A standard relay consists of an input circuit, which consists of positive and negative potentials, and an output circuit, which consists of common (COM), normally open (NO), and normally closed (NC) terminals.
2. Requirements for safety relays
In the field of automation and instrumentation, safety is a key factor in designing systems. Ordinary relays have the risk of mechanical contacts welding or sticking, which can cause system failure, especially in environments that require safety protection. In order to meet safety requirements, safety relays came into being. Safety relays have built-in self-monitoring functions that can detect contact failures and automatically shut down the circuit. They can be combined with other safety relays to provide comprehensive safety protection.
3. Characteristics of safety relays
1. Built-in self-monitoring function: It can detect the welding or jamming of contacts and automatically close the circuit.
2. Fault detection capability: It can detect the fault of input circuit to ensure the normal operation of safety functions.
3. Forced guided contacts: Even if the contacts are welded or jammed, they can be forced and mechanically guided to change position to ensure normal operation.
4. Communication interface: Integrated communication port facilitates the exchange of electrical data with other control devices.
5. Multiple applications: It is widely used in key equipment such as light curtains, safety mats, three-position devices, two-hand control devices, magnetic switches, emergency stop buttons, non-contact safety sensors, interlocking safety switches, etc.
4. Application of safety relays
Safety relays are suitable for field devices that require strict safety monitoring. They are able to detect problems such as line disconnection, faulty contactors, fail-safe actuators, short circuits, etc. By sending electrical pulses and measuring current flow, safety relays can quickly and accurately detect faults and take appropriate measures to ensure safety.
Use safety relays. Compared with ordinary relays, safety relays are more advanced and technologically advanced in operation. This ensures that it can be used in fail-safe environments. Safety relays are defined and manufactured to meet various SIL (Safety Integrity Level) applications.
Selecting a safety relay requires a good understanding of risk assessment factors and technology. Design can be viewed in ISO 12100 related standards.
Summary
Safety relays are important components for ensuring the safety of personnel and equipment in modern automation systems. Compared with ordinary relays, safety relays have built-in self-monitoring functions, forced guided contacts and fault detection capabilities, which can provide double safety protection.
Safety relays are widely used in scenarios that require strict safety monitoring, such as light curtains, safety mats, three-position devices, two-hand control devices, magnetic switches, emergency stop buttons, non-contact safety sensors, interlock safety switches, etc.
They can detect faults and ensure safety by taking corresponding measures. Safety relays play an important role in automation systems and provide an additional layer of protection for personnel and equipment.