Refrigerator automatic protector

The circuit is shown in the figure below, BT33 forms a delay circuit. When the power is first turned on, relay J1 does not work and contact J1-2 is disconnected. After five minutes, due to the increase in the charging voltage of capacitor C1, BT33 is turned on, relay J1 is closed, contact J1-2 is closed, and the refrigerator is powered on. , and is self-protected by the J1-1 normally open contact. Under normal voltage conditions, D2 and BG2 are on and D3, D4 and BG3 are off, so relay J2 does not work. When an overvoltage occurs, the voltage regulator tube D4 breaks down and conducts, BG3 conducts at the same time, the relay J2 is closed, the contact J2-1 is disconnected, the relay J1 is de-energized and released, and the refrigerator is powered off, which plays a role in protecting the refrigerator. When the power supply voltage is lower than the allowable value of the refrigerator (180V), D2 and BG2 will change from conduction to cutoff. The collector voltage of BG2 rises, causing D3 and BG3 to conduct, and the relay J2 will close, which will also cause the refrigerator to malfunction. Power outage.