Pump Three Phase Voltage Monitoring Relay , Under Voltage Over Voltage Protection Relay

principle of low protection

Low voltage protection of the motor This protection is often used in the motor control loops that drive the more important devices. The power of these motors is generally larger than other motors on the bus. The principle is to connect a low voltage relay in parallel with the motor trip circuit.

The normally closed contact, and the coil of the low voltage relay is connected in parallel between the two phases of the bus that provides the three-phase power for the motor. During normal operation, the power bus voltage is normal, and the low voltage relay coil is charged and returned in a return state. When the normally closed contact is open, the trip circuit will not be connected. When the bus loses power or a fault such as grounding occurs, the bus voltage drops to the low voltage relay action value, the relay will act, the normally closed contact will close, and the trip will be turned on. Circuit, remove the motor from the busbar. When the bus voltage recovers, the low-voltage relay returns and the normally closed contact is opened so that the trip circuit is also disconnected before the motor can be restarted. Because many devices are connected to the power bus, the loss of power to the bus or the voltage drop will cause many contactor coils to be de-energized and the devices controlled by the contactors will stop running. If the bus fault release voltage gradually recovers, many devices are After a sudden outage, particularly important equipment, DC power supply controlled circuit breakers are generally used to start and stop. After the AC power supply disappears, the DC power supply is normal, so after the trip, the closing operation can still be performed again.

If these devices are started at the same time, it is possible. Cause the bus voltage to reduce again, is not conducive to restore the normal operation of the equipment as soon as possible, so in these important large-scale equipment direct current control loop installs the low-voltage protection, first, after can guarantee the bus line breakdown eliminates, after the voltage return to normal can make these important The equipment is quickly restored to start, that is, the trip circuit is allowed to close after the trip circuit is open. Otherwise, the trip circuit is always on and is not allowed to start. Second, due to the installation of low-voltage protection, these large power devices cannot be started before the bus voltage does not return to normal. This can speed up the recovery of the bus voltage, which helps to shorten the fault time and reduce the other losses.

Features:

• Compact modular size
• Three-phase monitoring of phase sequence,phase loss,over-and undervoltage and phase unbalance
• Adjustable ober and undervoltage threshold(for JVRW)
• Powered by the measuring circuit
• 1C/O contact
• 5LEDs for status indicators

Protective Functions

• Phase Loass(Failure)
• Phase sequence( Reversal)
• Phase unbalance(Asymmetry)
• Undervoltage
• Overvoltage

Applications

• Pumps
• Fans
• Refrigeration Units
• Blowers
• Motors
• Compressors
• Lifts,Elevators
• Cranes
• Mining excavators and conveyors