Normally Open Contact Symbol

Energizing it and switching it on will close the contact causing it to allow current flow.

Normally open contact symbol.

Normally open switch contacts are sometimes referred to in the electrical industry as form a contacts. There is a common electrical connection between a contact of each pair that results in only three connection terminals. The following is a timing diagram of this relay contact s operation. Like the notc contact this type of contact is normally open when the coil is unpowered de energized and closed by the application of power to the relay coil.

This is the switch used to operate a doorbell. In other words when voltage is applied to the relay contactor terminals this contact closes. Push switch push to make a push switch allows current to flow only when the button is pressed. This symbol is used to indicate normally close contact.

On off switch spst spst single pole. Normally open is a contact that does not flow current in its normal state. Normally open no contacts allow current when the relay or contactor is energized. There is also a generic symbology for any switch contact using a pair of vertical lines to represent the contact points in a switch.

These terminals are usually labelled as normally open common and normally closed no c nc. Normally closed nc contacts allow current through when the relay or contactor is not energized. Relays and contactors have two types of contacts each suited for different applications. Next we have the normally open timed open noto contact.

The given symbol indicates a normally open contact. Usually at about 75 speed of motor. Also now is a good time to remind you that this is article is talking about the electrical normally open and normally closed symbols which while may look the same as the. If we had used a normally closed pushbutton switch instead the behavior would be exactly opposite.

Some of the most common and widely used symbols are given below 1. 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. In a schematic diagram the switch symbol appears to be a toggle switch with a flag hanging below. If the contact is normally open it would not allow any current to pass through it and hence there will be an open circuit at this contact.

Note the following symbols.