Normally Open Contact Symbol

The given symbol indicates a normally open contact.

Normally open contact symbol.

Note the following symbols. This symbol is used to indicate normally close contact. The contacts are nc normally closed and open when the back emf is high enough to pull the contacts open and take the start capacitor out of the circuit. Energizing it and switching it on will close the contact causing it to allow current flow.

If we had used a normally closed pushbutton switch instead the behavior would be exactly opposite. Normally open switch contacts are sometimes referred to in the electrical industry as form a contacts. This is the switch used to operate a doorbell. There is also a generic symbology for any switch contact using a pair of vertical lines to represent the contact points in a switch.

Push switch push to make a push switch allows current to flow only when the button is pressed. This type of push switch is normally closed on it is open off only when the button is pressed. 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. Normally closed nc contacts allow current through when the relay or contactor is not energized.

In other words when voltage is applied to the relay contactor terminals this contact closes. Normally open no contacts allow current when the relay or contactor is energized. Usually at about 75 speed of motor. 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.

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. Some of the most common and widely used symbols are given below 1. Normally open is a contact that does not flow current in its normal state. Next we have the normally open timed open noto contact.

On off switch spst spst single pole. There is a common electrical connection between a contact of each pair that results in only three connection terminals. In a schematic diagram the switch symbol appears to be a toggle switch with a flag hanging below. These terminals are usually labelled as normally open common and normally closed no c nc.

The following is a timing diagram of this relay contact s operation.