HYJ-IV-220VAC series three-phase power supply monitor is mainly used in three-phase AC 50 / 60Hz, rated voltage 150-300V circuit. It is a protecting relay that protect against over voltage or under voltage, open-phase , or reverse-phase. When the three-phase power supply is normal,the relay picks up, the normal-open contacts close, normal-close contacts cutoff, and the LED lamp shows ON. If any abnormal conditions occured for the power supply, the relay gets disconnected, normal-open contacts cut off, normal-close contacts close, the working LED lamp turns OFF, and the corresponding fault lamp is lit. Normal-open contact is linked in series circuit in the contactor coil loop, which can make the contactor lose of power, and cut off the motor power supply, thus to protect the motor from the damage.

2.Working principle

(1)Three-phase voltage unbalanced (phase loss) protection: The voltage unbalanced means that the negative sequence part is too large. Generally 1% of the voltage imbalance can cause 3% -11% phase current imbalance.Negative sequence part can not do work, and all will be converted to heat.So severe power supply voltage imbalance can cause the motor overheating and burned. At this condition,the ordinary equipped overload protector can not provide protection in time. When the voltage unbalance rate is higher than 8%, the protector operates ( time delay <1s).

Whether the equipment in running or not in running , any one phase open will go to the extreme condition of three-phase voltage imbalance.The three-phase voltage unbalance rate is 100% for static phase lack, and it will be more than 20% for dynamic phase loss. (If the phase loss occurs in the motor running, due to the EMF that generated from the running motor, the voltage won’t be zero at this phase. The way of protection will be decided by detecting the imbalance rate of the three-phase voltage ). If phase loss happens,the protector will take protective action quickly.In this condition,the NORMAL LED turns OFF, PHASE LOSS LED is ON, and the relay releases. And no detection will be carried on wrong phase and undervoltage fault!

(2)Wrong phase protection: If R,S,T are connected in right order, the NORMAL LED shows ON, and the relay picks up. Conversely, if R, S, T are connected in wrong order,the NORMAL LED shows OFF, and REVERSAL LED shows ON.

(3)Over voltage and under voltage protection: Three phase induction motor works at best under rated voltage. If the power supply voltage is too high, it will increase no-load excitation current in the motor. Hence the motor working efficiency will decrease, and it can also cause overheat in the motor. If the voltage is too low, the output power of motor will be decreased, which will cause overloads for the motor and may cause motor locked as severe cases. The voltage range for over-voltage and under-voltage protection can not be very narrow,otherwise it may make the protector act (ON /OFF)frequently. When the three phase average voltage is too high or too low and the OVER VOLTAGE or UNDER VOLTAGE LED shows ON,the relay won’t release unless the high voltage or low voltage lasts more than 8 seconds.

3.Electrical specification:

The protection function of the three-phase power supply monitor is not influenced by the line current, load current, surge current, unbalanced current, or the load property. It is able to work long hours with full performance under different climates.

♦Over voltage point:220VAC+12%*220VAC(tolerance 7V)

Reset voltage:10V less than the over voltage point

Time of protection:<3S

Time of recovery: <3S

♦Under-voltage point:220VAC-12%*220VAC(tolerance 7V)

Reset voltage:10V more than the under-voltage point

Time of protection:<3S

Time of recovery: <3S

♦Time of open phase protection:<3S

Time of recovery:<3S

♦ Unbalanced voltage:8%-10%

Recovery of unbalanced voltage: 25VAC

Time of unbalanced voltage protection:<3S

Time of recovery:<3S

♦Time of reverse-phase protection:<3S

Time of recovery:<3S

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