A safety relay is an automation component that is part of a machine’s safety system, thus contributing to the safety of people around it. The safety relay is a unique device. It has many differences from a normal relay.
Differences between a safety relay and a normal relay are described below.
1. Contact types
Unlike other relays, the safety relay has the function to detect its welding state and allows determination by the control circuit if contacts are welded together because it has guided contacts. This type of contact is mechanically connected. If a normally open (NO) or make contact remains closed, a normally closed (NC) or break contact cannot reclose. Additionally, if a normally closed (NC) contact fails to open upon energizing the relay, the NO contacts shall not close.
Normal relay has only mechanical contacts for switching.
The dimension of a safety relay is bigger than a normal relay. A safety relay is the product of advanced technology. It has many complicated circuits inside its construction.
A mechanical relay has a simple circuit. That’s why it is compact.
The safety relay has various switching, protection, and indication functions. For example, the safety relay protects people. It controls a user’s action to ensure that this does not lead to anything that may damage his health, either voluntarily or accidentally. Besides, when a machine may be dangerous for the user, it monitors all hazardous operations and detects the slightest anomaly. Normal relay is generally used for just switching in control circuits.
A normal relay is produced in different colors. (Mostly white) You can easily recognize a safety relay from its yellow color.
A safety relay is used for the combination of switches. Normal relay is used for linkage of contacts.
Safety relays are excellent for usage in safety applications. The most common applications for safety relays are e-stop circuits, safety gates, two-hand control, light curtains, safety mats, foot-operated switches, and interlocked gates.
But a normal relay can be used in almost any automation application. That is why the market size of a normal relay is huge.
8. Contact welding
In a safety relay application, if contacts are welded, the machine stops. But in a normal relay application, the machine would continue running until the operator pressed an emergency button.