Safety Relays. Also called “All–or–Nothing Relays with Positively Driven Contacts”. Relays of this type have contacts that are mechanically connected together, such that if a normally open (NO) or make contact remains closed, a normally closed (NC) or break contact can not re–close. Safety relays can detect faults at the input contacts in the safety circuit in the event of an earth fault. The safe function is guaranteed by specific internal circuits and relay technology. Safety relay modules and safety controllers are devices used in the safety-related part of control systems to perform control so that the machine operation is permitted only when safety is confirmed.
The main difference between safety relays and ordinary relays is that “safety relays” are not “relays without faults”, but make regular actions when failures occur. From studying the safety relay working principle, we can know that a safety relay is safer. A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
Safety Relays have forcibly guided contacts to prevent NO and NC contacts from operating at the same time during contact welding, which enables detection of contact welding in the Safety Relay itself. This can be used in building safety circuits. This means if you have an emergency stop pushbutton on a machine that has moving components or a process that could injure people, a safety relay will be required in order to maintain the safety rating of that component.
