Normally Open Relay Contact

We can tell this switch is a normally open no switch because it is drawn in an open position.

Normally open relay contact.

Relays and contactors have two types of contacts each suited for different applications. Form a contacts make contacts are normally open contacts. First we have the normally open timed closed notc contact. Relays are switches that open and close circuits electromechanically or electronically.

Normally closed nc contacts allow current through when the relay or contactor is not energized. 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. The lamp will energize only if someone presses the switch holding its normally open contacts in the closed position normally open switch contacts are sometimes referred to in the electrical industry as form a contacts.

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. 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. 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. 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. 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. Normally open no contacts allow current when the relay or contactor is energized.