Safety Relays

Relays are switches that open and close circuits. They control one electrical circuit by opening or closing contacts in another circuit. When a relay contact is normally open (NO), there is an open contact when the relay is not energized. When a relay contact is normally closed (NC), there is a closed contact when the relay is not energized. Applying electrical current to the contacts will change their state. Many relays use an electromagnet to mechanically operate a switch, but other operating principles such as solid-state relays are also used. Relays are used where it is necessary to control a circuit by a low-power signal or where several circuits must be controlled by one signal. Depending on the structural features and operating principle, relays are of different types such as monitoring, regulating, auxiliary and protective. Classification of the types of relays depend on the function for which they are used. 

Safety relays initiate safe and reliable responses in the event of a hazard to protect equipment and operators. Each safety relay monitors a specific function. Typical functions include initiating the controlled interruption of a device or machine in order to stop movements safely. For example, monitoring the position of moveable guards, interrupting their closure during access. They can also be used as an emergency shutdown mechanism by shutting off the power to specific systems or equipment. Multiple safety relays can be interconnected in order to fully monitor a machine or system.