When the ironing machine is at room temperature, the contacts at both ends of the bimetallic strip contact the contacts on the elastic copper strip. When the soldering iron head is connected to the power supply, the current flows through the copper sheet and bimetallic sheet in contact with the heating wire. The heating wire generates heat and transfers it to the metal base plate at the bottom of the ironing machine. People can use a heated floor to iron clothes. With the increase of power on time, when the temperature of the bottom plate rises to the set temperature, the bimetallic sheet fixed on the bottom plate is heated and bent downward, and the contact on the top of the bimetallic sheet is separated from the contact on the elastic element. Copper plate. The circuit is damaged. At this time, the temperature of the bottom plate is no longer increased, and it is reduced due to the heat dissipation of the bottom plate; The deformation of the bimetallic strip gradually recovers. When the temperature drops to the specified value, the bimetallic sheet and the elastic copper sheet contact again, the circuit is connected again, and the temperature of the bottom plate starts to rise again. In this way, when the temperature is higher than the required temperature, the circuit is disconnected, and when the temperature is lower than the required temperature, the circuit is connected, and the temperature can be kept within the specified range.

When the temperature control knob is adjusted upward, the upper and lower touch points will move upward accordingly. Bimetallic contacts can be separated by bending slightly. Obviously, the temperature of the bottom plate is low at this time, and the bimetal can control the constant temperature of the bottom plate at a lower temperature. When the temperature control knob is put down, the upper and lower contacts will move down accordingly, and the bimetallic contact can be separated only when it is bent at a greater angle. Obviously, the temperature of the bottom plate is high at this time, and the bimetal can control the constant temperature of the bottom plate at a higher temperature. In this way, it can adapt to different temperature requirements of the fabric.

In the range of positive temperature coefficients, the current flowing through the element increases, the power increases, and the temperature of the element increases, which increases the resistance value, which leads to a decrease in current and a decrease in power. When the temperature rise caused by electricity is balanced with heat dissipation, the temperature and resistance will not change. This automatic control function of PTC module is usually used for current control and temperature control of electronic equipment, and also used to manufacture thermostatic heaters, such as electronic soldering iron, dryer and mosquito killer. The volt ampere characteristics of PTC components can be derived from the resistance temperature characteristics.

If the current flowing through the PTC module suddenly increases for some reason, the suddenly increased electrical power will quickly make the module have high resistance, so that the current will drop to near zero, and play a "self limiting" role and temperature on the current. Therefore, PTC components can be used for overcurrent protection and overheating protection of electronic equipment, such as motor overheating protection. The current time characteristics of PTC elements show that the current delay process is from large to small. This delay function is usually used to start the motor and refrigerator compressor. PTC elements are connected in series in the starting winding. When the power is turned on, the PTC element is in a low resistance state, so a large current flows through the starting winding group. After starting, the PTC element is in a high impedance state, so the current is very small, and there is only a large current in the running winding. In short, the structure and parameters of PTC components are different and can be used in different occasions.