First we have the normally open timed closed notc contact.
Normally open relay means.
Normally closed nc contacts allow current through when the relay or contactor is not 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.
Normally open relays default in the open position meaning that when they re not in use there is no contact between the circuits.
The following is a description of the four basic types of time delay relay contacts.
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.
Of these contact forms the following are particularly common.
Relays and contactors have two types of contacts each suited for different applications.
Normally open switch contacts are in an open state at rest.
In other words when voltage is applied to the relay contactor terminals this contact closes.
Form a contacts make contacts are normally open 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.
What is open and closed.
Before we get into what normally open and normally closed are let s clarify what open and closed mean.
Meaning pronunciation translations and examples.
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.
Normally open no contacts allow current when the relay or contactor is energized.