Overvoltage and overcurrent protection circuit

Overvoltage and overcurrent protection circuit

Unstable grid voltage can easily damage electrical equipment in your home. The use of overvoltage and overcurrent protection circuits can prevent harm caused by unstable grid voltage
, and can also limit the load power output of household appliances to prevent overcurrent and short circuit protection. The circuit is as shown in the figure.
    When the battery voltage is within the rated range - relay K1 does not operate and K2 operates to close. LED2 (green light) lights up to indicate that the load is connected
and working.
    When the grid voltage exceeds the rated value, the secondary side output of transformer T1 also increases. The thyristor VTH1 is
turned on through the resistors R2, Ra and RP1, and the relay Kl is closed. LED1 green light lights up to indicate, Kl normally closed contact disconnects the load.
    When the load circuit is short-circuited or exceeds the rated output power, the induced voltage at the W2 terminal of the current transformer T2 increases. Rectified by VD1, resistors
R,, R, RP3. The thyristor VTH1 is turned on, the relay is activated, and the load circuit is disconnected.
    Debugging: Use a voltage regulator to adjust the voltage to 180V, then connect a human circuit to adjust RP2. Make the thyristor VTH2 conduct, and the relay K2 pulls in
(to ensure that vsz can cut off when it is lower than 175V, and K2 is disconnected)} Adjust the voltage regulator again to make the output voltage to 240V, adjust RP1, make
VTH1 conduct, and the relay Kl pulls in ( When it is lower than 235V, VTH1 is guaranteed to be cut off and relay Kl can be released). The
    over-current protection adjustment t is connected to a load of 3000W, and RP3 is adjusted until the relay Kl can be closed. Household electrical power is generally
below 3000W. If a large load is required, RP3J can be adjusted to change the rated load.
  Component selection: The transformer uses an MX0-2000 magnetic ring, and Wl is wound with 5 turns of @1. 2mm enameled wire. W2 is wound with 600 turns with < pO. 2mm.
The thyristor is MCR1008. Relays Kl and K2 use electromagnetic relays above 24V/10A.