New power interruption technology based on Mott device

Korean researchers have developed an innovative power interruption technology based on a Mott metal-insulator transition (Mott MIT) device.

The device is said to reduce the size and enhance the performance of traditional electromagnetic switches and circuit breakers. The Mott MIT signifies the phenomenon that a Mott insulator can be abruptly converted into a metal — or vice versa — without the structural phase transition. 

Dr Hyun-Tak Kim of Korea’s Electronics and Telecommunications Research Institute led the team that developed the device. The research team previously developed a Mott MIT critical temperature switch (CTS) (or MIT device) which generates a control current (or signal) at a critical temperature between 67°C and 85°C as the unique characteristic of vanadium dioxide. 

After that, the MIT devices were applied to types of electromagnetic switches that interrupt an electric current in case of overcurrent.

A traditional electromagnetic switch — which takes the role of interrupting electricity through the mechanical switching when it conducts an overcurrent — is composed of both an electromagnet called the magnetic contactor, which connects or disconnects signals of main power, and the thermal overload relay, with an on-off switching function controlled by temperature. 

The overload relay is composed of both an expensive delicate mechanical switch with a large size and a bimetal that is made of two separate metals with different thermal expansion coefficients joined together. The bimetal has the characteristic of bending in any direction when heat is applied. The bending force of the bimetal controls the mechanical switch inducing the on-off switching. However, the bimetal undergoes a change in this bending characteristic during long-term usage; therefore, the accuracy of the overload relay drops. Finally, the performance of the electromagnetic switch deteriorates; this is a fatal problem with the traditional electromagnetic switch.

In order to solve the problem, the research team used the MIT-CTS instead of the bimetal as a sensor for the on-off switch. In this case, the mechanical switch is replaced by a simple electrical circuit controlling the electromagnet, which means that the mechanical switching is changed into the electronic one. Therefore, the MIT overload relay becomes small in size by removing the large mechanical switch and has accuracy irrespective of environmental temperature. Accordingly, the MIT electromagnetic switch has a reliable and accurate electronic switching characteristic.