Normally Open Relay Contact

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 relay contact.

Of these contact forms the following are particularly common. The no normally open spst single pole single throw relay has an opened circuit state when no current is applied to its coil so basically it disconnects the power to the load in the inactive state. The circuit is connected when the relay is inactive. The state conditions normally open no and normally closed refer how the contacts sit when the switch is off relay coil voltage is 0 etc.

If it is a switch then it is off. Normally closed nc contacts disconnect the circuit when the relay is activated. Form a contacts make contacts are normally open contacts. As relay diagrams show when a relay contact is normally open no there is an open contact when the relay is not energized.

If it is a relay then it is not energized. When a relay contact is normally closed nc there is a closed contact when the relay 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. If it is a high limit such as a temperature alarm then the current temperature is below the limit.

In other words when voltage is applied to the relay contactor terminals this contact closes. When voltage is applied this contact opens and interrupts current. Normally closed nc contacts allow current through when the relay or contactor is not energized. When current is applied to its coil the generated magnetic field switches the armature and closes the contact so you can say that it turned on the load fan light bulb etc.

Unlike open contacts with normally closed contacts signal will interrupt a contact or turn a relay off. When the energizing force is present the contact will close. Normally open is a contact. Normally open no contacts connect the circuit when the relay is activated.

The contacts are open when the energizing force magnet or relay solenoid is not present. A form a would mean the contacts are normally open when the coil of the relay is not energized or the there is no magnetic field nearby in a reed switch. Normally open contacts would represent relay contacts that would perform a connection upon receipt of a signal. Normally open no contacts allow current when the relay or contactor is energized.

A form b would mean the contacts are normally closed when the coil of the relay is not energized or the there is no magnetic field nearby in a reed switch. Relays control one electrical circuit by opening and closing contacts in another circuit. The circuit is disconnected when the relay is inactive. A form c would.