Principles and methods of non-contact DC contactors calculation for alternative power systems

Abstract

It is shown that the principle of control and power supply of a non-contact bi-directional DC contactor by the electrical line voltage is implemented by connecting the electronic control circuit by one output between two opposite powered gate-controlled thyristors of the bilateral switch to the first pole of the contactor and the second one – to the output clamp. As a result, the electrical line voltage is fed to the electronic circuit only for a short time (up to ms), that is determined by the charge time of the switching capacitor to the breakdown voltage of the threshold zener diode. The peculiarities of the heating process of the power semiconductor contactor in different operating conditions were determined, that allowed to develop a methodology that with sufficient accuracy determines such important parameters as rated and operational current of the contactor. In addition, it was found that in order to reduce significantly the capacity of the switching capacitor, and consequently the size and cost, it is necessary while turning on of the switching thyristor the discharging current of the switching capacitor was equal to the current of its charging circuit, and their values should not be less than the maximum allowable current of turning off the gate-controlled thyristor. It is allows to define justified the parameters of the elements that provide a secure turning off the bilateral switch. The researches have also shown that the non-contact contactors due to the introduction of the network voltage control as compared with existing ones have peculiarities which rise competitive abilities. In particular, they are more reliable, they do not need to supply an additional power source, they exclude standard drivers, and minimize energy consumption. Thus, an exemplary aspect of using the obtained scientific result is the ability to create competitive reliable non-contact DC contactors for voltage up to 1000 V and currents of 100-600 A for alternative energy. Key words – non-contact bi-directional DC contactor, switching capacitor, switching thyristor, power semiconductor switch, alternative energy.