Normally Open Relay Contact

Form a contacts make contacts are normally open contacts.

Normally open relay contact.

First we have the normally open timed closed notc contact. The following is a description of the four basic types of time delay relay contacts. 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 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.

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. We can tell this switch is a normally open no switch because it is drawn in an open position. Relays and contactors have two types of contacts each suited for different applications. 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.

Of these contact forms the following are particularly common. Relays control one electrical circuit by opening and closing contacts in another circuit. Relays are switches that open and close circuits electromechanically or electronically. In other words when voltage is applied to the relay contactor terminals this contact closes.

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 closed nc contacts allow current through when the relay or contactor is not energized. As relay diagrams show when a relay contact is normally open no there is an open contact when the relay is not energized.