Normally Open Relay Contact

Relays and contactors have two types of contacts each suited for different applications.

Normally open relay contact. Form a contacts make contacts are normally open contacts. Normally open no contacts allow current when the relay or contactor is energized. When power is introduced an electromagnet pulls the first circuit into contact with the second thereby closing the circuit and allowing power to flow through. In other words when voltage is applied to the relay contactor terminals this contact closes.

Normally open and normally closed electrical contacts make up electrical switches relays circuit breakers and most any other electrical component that switches something on off or can be switched on off. Relays control one electrical circuit by opening and closing contacts in another circuit. Normally closed nc contacts allow current through when the relay or contactor is not energized. Time delay relay contacts must be specified not only as either normally open or normally closed but whether the delay operates in the direction of closing or in the direction of opening.

Of these contact forms the following are particularly common. As relay diagrams show when a relay contact is normally open no there is an open contact when the relay is not energized. We can tell this switch is a normally open no switch because it is drawn in an open position. Normally open single pole single throw spst relay in figure 1 no dc voltage is applied to points a and b therefore no current flows through the coil of the relay the contact stays in the opened position and the fan will not be switched on because it s disconnected from the 220v.

First we have the normally open timed closed notc contact. The national association of relay manufacturers and its successor the relay and switch industry association define 23 distinct forms of electrical contact found in relays and switches. The following is a description of the four basic types of time delay relay contacts.