Normally Open Contact Means

When it comes to electrical switches and contacts many people seem to be confused by the terms normally open no and normally closed nc the root of the problem seems to start with the fundamental concept of what it means to be open or closed this post attempts to clarify those concepts.

Normally open contact means.

Normally open switch contacts are in an open state at rest. Normally open contacts or switches with the normally open switching function are well known in daily life such as with light switches. These terminals are usually labelled as normally open common and normally closed no c nc. 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.

What is open and closed. Normally open relays default in the open position meaning that when they re not in use there is no contact between the circuits. A light switch is generally a normally open contact which on actuation closes a circuit and thus allows the current to flow to the series connected light bulb see fig. Meaning pronunciation translations and examples.

Normally open no contacts allow current when the relay or contactor is energized. There is a common electrical connection between a contact of each pair that results in only three connection terminals. But what exactly defines normal for a switch. Form c contacts change over or transfer contacts are composed of a normally closed contact pair and a normally open contact pair that are operated by the same device.

As with so many topics that we try to simplify by associating with something we are familiar with associating electrical current flow with water flow causes a tremendous amount of misunderstandings. Normally open vs normally closed electrical switch contacts. When replacing an existing contact you also need to know if the contact being replaced was normally open or closed especially if more than one contact is wired into a zone. In other words when voltage is applied to the relay contactor terminals this contact closes.

When buying contacts look for form c spdt single pole double. Electrical switch contacts are typically classified as either normally open or normally closed referring to the open or closed status of the contacts under normal conditions. Relays and contactors have two types of contacts each suited for different applications. Before we get into what normally open and normally closed are let s clarify what open and closed mean.