At present, there are many choices of hot water kettle, even remote control. Just because the electric kettle is plugged in does not mean that it will automatically boil water, because it has its own anti-electricity device, which brings a convenient and safe environment for users who need different water temperatures. The principle of automatic power cut has several aspects:

1. According to the principle that objects expand when heated and contract when cooled.

Thermal expansion and cold contraction are characteristics of objects, but different objects have different degrees of thermal expansion and cold contraction. The contacts are made of copper sheet metal. Because copper is sensitive to thermal expansion and contraction, when the temperature does not reach the set value, the copper metal sheet will bend. At this point, its contacts are closed and connected. When the water is heated to the set temperature, the heat of the water will be conducted to the copper sheet in the thermostat, and the copper sheet will bounce off the contact to the power-off state because of being straightened by the heat. When the temperature drops, the copper sheet will return to its original state, so that the contact will be powered on and heated. Both sides of the bimetal are conductors of different substances, so that the bimetal will bend due to different expansion and contraction degrees at changing temperatures, and touch the set contacts or switches, so that the set circuit starts to work. This is more direct and timely, and can accurately sense the water temperature.

2. Automatic temperature control circuit

There is an automatic temperature control circuit in the kettle when the water in the kettle is boiled dry. The circuit is connected in series with the temperature sensor. The boiling point of water is 100 degrees. When the water boils dry, the temperature sensor will break the circuit. Simple temperature sensor is bimetal, which is often used in electric irons, water heaters and other electrical appliances. There are many kinds of temperature sensors, as well as semiconductor temperature sensors. This structure is simple, safe and reliable.

3. Steam temperature of water

The automatic power-off function is generally realized by a bimetallic thermostat located at the upper part of the water cup and the inside of the handle (or at the bottom of the cup, which requires a long air duct). There is no relay or thermistor inside, and it feels the temperature of steam released by water, so it is indirect. Generally, only after the water boils can the steam temperature reach the disconnection point of the thermostat. So, if you open the lid to boil water, it won't automatically disconnect.