Normally Open Contact Symbol

Normally open is a contact that does not flow current in its normal state.

Normally open contact symbol.

Relays and contactors have two types of contacts each suited for different applications. Normally open switch contacts are sometimes referred to in the electrical industry as form a contacts. 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. The following is a timing diagram of this relay contact s operation.

Normally open no contacts allow current when the relay or contactor is energized. In other words when voltage is applied to the relay contactor terminals this contact closes. Normally open contacts are designated by the lines not touching while normally closed contacts are designated with a diagonal line bridging between the two lines. In a schematic diagram the switch symbol appears to be a toggle switch with a flag hanging below.

Energizing it and switching it on will close the contact causing it to allow current flow. Usually at about 75 speed of motor. These terminals are usually labelled as normally open common and normally closed no c nc. This type of push switch is normally closed on it is open off only when the button is pressed.

The given symbol indicates a normally open contact. Some of the most common and widely used symbols are given below 1. 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. On off switch spst spst single pole.

Next we have the normally open timed open noto contact. This is the switch used to operate a doorbell. If we had used a normally closed pushbutton switch instead the behavior would be exactly opposite. 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. 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. Normally closed nc contacts allow current through when the relay or contactor is not energized. This symbol is used to indicate normally close contact.

Note the following symbols.