Undervoltage release the power supply voltage is equal to the rated working voltage release

The MCB has delayed or disconnected without delay a trip, when the supply voltage drops (or even slow down) to the rated working voltage of 70 to 35 percent range, under voltage release should operate under voltage release the power supply voltage is equal to  air circuit breaker  35% of rated voltage when undervoltage release should be able to prevent the MCB is closed; supply voltage is equal to or greater than 85%  mcb circuit breaker  release the rated  electric meter , should guarantee MCB reliable closure. Therefore, when the power supply voltage by the protection circuit in a voltage drop occurs, automatically open the MCB cut off, so that the electrical load of the following MCB or electrical equipment from damage due to voltage.