Normally Open Relay Contact Symbol

The following is a description of the four basic types of time delay relay contacts.

Normally open relay contact symbol.

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. Changeover contact this is the changeover contact of a relay that is closed or connected with one terminal known as normally closed terminal when the relay is deactivated the other terminal. Of these contact forms the following are particularly common. 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.

Normally open no contacts allow current when the relay or contactor is energized. First we have the normally open timed closed notc contact. The contacts open when the relay activates to break the circuit. Relays and contactors have two types of contacts each suited for different applications.

Now let s go through a real world example of normally open and normally closed contacts that we are all familiar with. 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.

It is the contact of relay that is in closed position when there is no power supplied. Normally closed nc contacts allow current through when the relay or contactor is not energized.