Normally Open Relay Contact Symbol

The contacts open when the relay activates to break the circuit.

Normally open relay contact symbol.

Form a contacts make contacts are normally open contacts. Now let s go through a real world example of normally open and normally closed contacts that we are all familiar with. Rarely are these familiar examples good for learning but a 3 way switch is an excellent example of using normally open and normally closed switches. Of these contact forms the following are particularly common.

First we have the normally open timed closed notc contact. Normally closed nc contacts allow current through when the relay or contactor is not energized. Normally open no contacts allow current when the relay or contactor is energized. Relays and contactors have two types of contacts each suited for different applications.

In other words when voltage is applied to the relay contactor terminals this contact closes. 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. The relay are switching devices activated by signals. 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.

Most of the time a small voltage or current is used to switch other voltages or higher currents that may be electromechanical or fully electronic type. The following is a description of the four basic types of time delay relay contacts.