How To Distinguish Between Normally Open And Normally Closed Contacts Of Current Relays?

How to distinguish between normally open and normally closed contacts. Relays are actually divided into normally open and normally closed contacts. Normally closed contacts are the two ends when the resistance value is zero, but this value is generally a few ohms, which can be measured with a multimeter and the resistance can be measured.

When selecting a current relay, you must consider the input voltage, current, output load, and peak voltage. The figure below shows the DC input 12V to control the AC load. At this time, if the output is 220V, the general current is 50%. But, a little conservative can use 70%, that is, 5A and 7A.

Current relay contacts normally open to normally closed when power is on, and normally closed to normally open when there is no power

After the current relay is connected to the power supply, the normally open is closed, and the normally closed is open. Instead of what you said, "As long as there is current, the normally closed point of the current relay should not open and become a normally open point." Normally open and normally closed refer to the state of the contacts when the current relay coil is not energized. As for the normally closed connection as a protection circuit, for example, the motor forward and reverse control circuit does not allow the forward contactor and the reverse contactor to be attracted at the same time. It is necessary to string the normally closed auxiliary contacts of the forward contactor to the coil circuit of the reverse contactor, and string the normally closed auxiliary contacts of the reverse contactor to the coil circuit of the forward contactor. In this way, the normally closed auxiliary contact is disconnected when the forward contactor is closed, so that the coil circuit of the reverse contactor is open and cannot be connected. vice versa. This plays a protective role.

String the normally closed auxiliary contact of the forward contactor to the coil circuit of the reverse contactor, and string the normally closed auxiliary contact of the reverse contactor to the coil circuit of the forward contactor. In this way, the normally closed auxiliary contact is disconnected when the forward contactor is closed, so that the coil circuit of the reverse contactor is open and cannot be connected. vice versa. This plays a protective role.