The application of ceramic PTC auxiliary electric heater in air duct machine
Commercial air conditioners use electric heating tube heaters as auxiliary heating tools. Its advantage is that the electric heating tube is a pure resistive load, and the power is easy to determine. The disadvantage is that it can only achieve on and off control, not automatic temperature control, and the surface load is limited. , In a limited structure, the power cannot be too high, and the temperature rises slowly under a low room temperature, which caused some customers to complain that the heating effect is not obvious. In addition, in the new generation of air duct machines developed by the company, the shell is structurally compressed as small as possible, and a foam drain pan is used, which makes the distance between the auxiliary electric heater and the drain pan about 2 to 3 cm. In this way, when the simulated temperature limiter fails and the dry burn test is not working properly, when the fuse is blown and the electric heating circuit is disconnected, the foam has been severely deformed and even volatilized. Ceramic PTC (positive temperature coefficient, positive temperature coefficient) is a kind of thermal element based on the phase change of Ba TiO3 ceramic crystal at high temperature. The ceramic PTC heating element is made of aluminum tube as the shell, ceramic PTC sheet as the heating element, with lead rods at one or both ends, and aluminum corrugated sheet as the heat sink, which is fixed as an integral element by silicone bonding. Its characteristic is that the resistance is very small at room temperature, and the resistance increases step by step with the increase of temperature after power-on, rapidly rising to the Curie temperature point Tc, and then running stably in the range of Tc ~ Tp. When the surface temperature of dry burning increases, due to the increase of resistance, its sensitivity to temperature will automatically adjust the power and finally reduce the temperature to the equilibrium point.