What is the difference between safety relay and general relay?
1) Larger appearance: the overall dimensions of the safety relay are different from those of the ordinary relay, and the safety relay is larger.
2) Module rather than component: safety relay is a module rather than an electronic component like ordinary relay.
3) Red and yellow: the safety relay has a special color, usually yellow, or red, or these two colors are the main colors (just as our explosion-proof safety design, dangerous side and intrinsically safe end are usually marked with blue). Of course, these are only superficial phenomena.
4) [core] safer: due to differences in design principles, ordinary relays cannot achieve high diagnostic coverage (DC) and can only be applied to machinery industries with lower safety levels, such as cat.b/1 and sil1 in process control industry. Therefore, it can be considered that ordinary relays are not safe enough. Through the requirements of relay and the auxiliary design of logic circuit, the diagnostic coverage of Anji is high, and some can reach 99.9%. Moreover, in some occasions with high safety requirements, it is also stipulated that the certified safety relay must be used to meet the safety requirements!
5) Mandatory guiding structure: "safety relay" is not a "relay without fault", but a regular action when a fault occurs. The safety relay has a forced guide contact structure (or other protection methods), which can ensure safety in case of contact melting and welding, which is completely different from the general relay.
6) From the perspective of relay, we can see the difference between safety relay and ordinary relay:
The core component of the safety relay is the forced pilot relay. From the perspective of the relay, we can see the difference between the safety relay and the ordinary relay.
Common relay: the fusion of contacts will make two pairs of contacts (no/nc) on at the same time.
Forced pilot relay: under the action of the internal forced pilot rod, even if the contact is fused, the two pairs of contacts (no/nc) will not be on at the same time. The forced guiding structure is a simple and effective way to detect the contact fusion fault.
In short: the safety relay is safer and more reliable, and is suitable for industrial safety occasions.