What is zero pressure relay?
Under normal circumstances is achieved with SCR, the detection of AC voltage zero when the open SCR, the current zero off when the zero. This can reduce the electromagnetic interference to other devices.
Crane zero protection refers to the crane connected to the power, the controller rear handle must pass zero, the crane to start. Zero is a supplement to the loss of pressure protection, it can prevent the crane connected to power after the malfunction. Pressure protection and zero protection, usually by the zero-voltage relays, the main contactor, electrical contacts, manual reset the master controller or cam controller and other control circuit to achieve its function
In the three-phase circuit at the midpoint of zero and ground access to a relay, when the three-phase circuit is not balanced when the zero line voltage, the relay action, play a protective role.
The voltage relay is a commonly used electromagnetic relay, and the Mirenle S2 series voltage relays are used for voltage protection and control of electric drive systems. The coil connected in parallel to the main circuit, sensing the main circuit of the line voltage; contact connected to the control circuit for the implementation of components. According to the size of the pull-in voltage, the Mirenle S2 series voltage relays can be divided into overvoltage relays and undervoltage relays. Overvoltage relay (UV) for the line over-voltage protection, the suction set value for the protection line rated power 1.05 ~ 1.2 times. When the protected circuit voltage is normal, the armature does not move; when the voltage of the protected circuit is higher than the rated value, when the setting value of the overvoltage relay is reached, the armature pulls, the contact mechanism moves, the control circuit is de-energized, Timely cut off the protected circuit. Undervoltage relay (OV) for the line undervoltage protection, the release setting value for the line rated voltage of 0.1 to 0.6 times. When the protected circuit voltage is normal, the armature reliable pull; when the protected circuit voltage drops to the undervoltage relay release setting value, the armature release, contact mechanism reset, control contactor in time to break the protected circuit. Zero voltage relay is released when the circuit voltage is reduced to 5% ~ 25% UN, the circuit to achieve zero voltage protection. For the line of pressure protection. The intermediate relay is essentially a voltage relay. It is characterized by a large number of contacts, the current capacity can be increased, play the middle of the amplification (the number of contacts and current capacity) role.
