How A Rice Cooker Works

The main structure of an ordinary rice cooker is composed of a heating plate, a temperature limiter, a heat preservation switch, a lever switch, a current limiting resistor, an indicator light, and a socket.

hot plate

This is the main heating element of the rice cooker. It is an aluminum alloy disc with a built-in electric heating tube, the inner pot is placed on it, and you can see it when you remove the inner pot.

temperature limiter

Also called a magnet. It is equipped with a permanent magnetic ring and a spring, which can be pressed and located in the center of the heating plate. When cooking rice, when the cooking switch is pressed, the lever switch is driven by the suction force of the magnetic steel to keep the power contacts connected. When the rice is cooking, the temperature of the bottom of the pot increases continuously, and the suction force of the permanent magnetic ring increases with the temperature. When the water in the inner pot is evaporated and the temperature of the bottom of the pot reaches 103 ± 2°C, the suction force of the magnetic ring is less than the elastic force of the spring on it, the temperature limiter is pushed down by the spring, and the lever switch is driven to cut off the power. 

keep warm switch

Also called a thermostat. It consists of a spring sheet, a pair of normally closed contacts, a pair of normally open contacts, and a bimetallic sheet. During cooking, the temperature in the pot rises, and the bimetallic sheet is bent upward due to the different thermal expansion and contraction rates of the two metal sheets constituting the bimetallic sheet. When the temperature reaches above 80°C, under the push of the upwardly bent bimetallic sheet, the spring sheet drives the normally open and normally closed contacts to switch, thereby cutting off the power supply of the heating tube and stopping the heating. When the temperature in the pot drops below 80°C, the bimetallic sheet gradually cools down and recovers, the normally open and normally closed contacts are switched again, and the heating tube power is turned on for heating. Repeat this to achieve the thermal insulation effect.

lever switch

The switch is completely mechanical, with a normally open contact. When cooking rice, press this switch to connect the power to the heating tube, and at the same time supply power to the heating indicator to light it. When the meal is ready, the temperature limiter pops down and drives the lever switch to disconnect the contacts. After that, the heating tube is only controlled by the heat preservation switch.

Current limiting resistor

The appearance is golden yellow or white, and the size is like a 3W resistor. It is pressed between the heating tube and the power supply to protect the heating tube. The commonly used current limiting resistor is 185C 5A or 10A (depending on the power of the rice cooker). The current limiting resistor is the key element to protect the heating tube and cannot be replaced by a wire.