This paper proposes an analytical model of maximum operating frequency of class-D zero-voltage-switching (ZVS) inverter. The model includes linearized drain-source parasitic capacitance and any duty ratio. The nonlinear drain-source parasitic capacitance is equally linearized through a charge-related equation. The model expresses the relationship among frequency, shunt capacitance, duty ratio, load impedance, output current phase, and DC input voltage under the ZVS condition. The analytical result shows that the maximum operating frequency under the ZVS condition can be obtained when the duty ratio, the output current phase, and the DC input voltage are set to optimal values. A 650 V/30 A SiC-MOSFET is utilized for both simulated and experimental verification, resulting in good consistency.

We proposed a method for suppressing arc ignition in mechanical contact devices using a transient current switch and a capacitor. We applied the method to conventional reed switches. For the electric circuit analysis, we clarified the momentary voltage-current characteristics at breaking operation of reed switches by FEM analysis. We could also estimate the capacitance of the contact electrodes at the metal bridge rupture by FEM analysis, and would derive the non-arcing condition using SPICE simulation. The suitable capacitor value in the transient current circuit for arc ignition suppression would be depend on the load impedance, the power supply, the time depending contact resistance R(t)s, the contact capacitance, and the minimum arc voltage and current.

We propose a new electric contact device that greatly improves arc discharge characteristics. Electric contact functions are divided into an energizing operation and a switching operation. A capacitor is connected in series to a contact for switching contact. Using two conventional relay contacts, no arc operation is confirmed for a 42 V/3 A break operation. Contact resistances are measured over many operations, and the surfaces of electrodes are observed. A chip capacitor is arranged at one side of the contact electrodes of a twin relay, confirming the possibility of miniaturization.

A LiNbO3 piezoelectric actuator controls the Au-Au contact gap. The control accuracy of the actuator is within the sub-micron range. Contact voltage, contact current, displacement of electrodes and driving voltage of the actuator were continuously and synchronously recorded by an A/D converter and send to a computer. The measured oscillograph data for 1500 contact operation were processed by the computer. Factors of discharge and bridge phenomena were derived at a contact operation. The delay time between displacement and driving signal of the actuator increased when one side of electric contact were vibrated. The resonance was seen in the actuator, and the dependency to the current and the amplitude was seen.

We proposed a new electric contact device that suppresses the arc phenomena. The functions of electric contacts are divided into energizing and switching for arc suppression. Switching contacts consist of multielectrodes and each electrode current is suppressed by the series resistance. For realization of multicontacting, cantilever beam array electrodes were formed on a silicon substrate using micro-electromechanical systems (MEMS) technology. The finite element method was used to optimize the structure. The fabrication process of the cantilever was examined. Au-Au contact current of 0.97 A was broken without arc ignition.

We propose a new electric contact device for arc discharge suppression. The functions of conventional electric contacts are categorized into energizing switch contacts and transient current switch contacts. A capacitor is connected in series to a transient current switch. Suppression of power consumption and arc discharge at breaking contacts are proposed, experimentally measured, and theoretically analyzed. The transient V-I characteristics at breaking contacts are controlled by the transient current switch and the capacitor. The transient responses at contacts were numerically derived by SPICE, and the energizing switch contacts voltage could be controlled to less than the minimum arc voltage. Using 2 conventional relays, no arc ignition at breaking contacts was confirmed for 50 V/25 A.