Troubleshooting of automatic heat preservation of rice cooker.

The circuit board of the rice cooker cannot automatically enter the stewing and heat preservation state. It may be that the contact can't be disconnected due to ablation, the main thermostat is abnormal or the main circuit board is damaged, so it is necessary to replace the main thermostat or the main circuit board.

Heating circuit principle

The heating circuit is mainly composed of heat-sensitive soft magnets and permanent magnets. The temperature-sensitive soft magnet is fixed with the heating surface, and the heat at the bottom of the inner pot is directly transferred to it through the heating surface. When the temperature is lower than 103℃, the temperature-sensitive soft magnetic has the same magnetism as the permanent magnet, and when the temperature is higher than 103℃, the temperature-sensitive soft magnetic will suddenly lose its magnetism.

Starting switch principle

When cooking, press the start switch by hand, and the transmission rod attracts the permanent magnet and the soft magnet. The attractive force is greater than the elastic force of the spring and the self-weight of the permanent magnet, so the permanent magnet will not fall, the contact is closed, the circuit is connected, and the heating plate begins to heat.

Principle of temperature limiting action

When the rice is cooked, the temperature continues to rise. When it reaches 103℃, the soft magnet suddenly loses its magnetism, and the permanent magnet falls under its own gravity and spring force. The contacts are separated by the transmission rod, the circuit is disconnected, and the heating plate stops heating. This will play a role in limiting the temperature.

Thermal insulation principle

When the temperature drops, the bimetal gradually recovers. When the temperature is lower than the insulation temperature, the position of the moving plate is lower than the fulcrum. Under the action of the energy storage elastic sheet, the contact is closed and the circuit is connected. In this way, although the temperature limiter has been disconnected, the continuous function of the heat insulator can achieve the purpose of heat preservation.