Abstract: A wiring board includes: a ceramic board including a ceramic insulator layer composed mainly of ceramic, and a wiring disposed at the ceramic insulator layer; a first resin board and a second resin board each of which includes a resin insulator layer composed mainly of resin, and a wiring disposed at the resin insulator layer; and a metal member mounted to the second resin board. The first resin board is superposed to a first surface of the ceramic board. The second resin board is superposed to a second surface of the ceramic board opposite to the first surface of the ceramic board. The second resin board includes a joint pad at its first surface opposite to its second surface facing the ceramic board, the joint pad made of metal. The metal member is joined to the joint pad by brazing or soldering.

Abstract: A wiring board includes: a ceramic board including a ceramic insulator layer composed mainly of ceramic, and a wiring disposed at the ceramic insulator layer; a first resin board and a second resin board each of which includes a resin insulator layer composed mainly of resin, and a wiring disposed at the resin insulator layer; and a metal member mounted to the second resin board. The first resin board is superposed to a first surface of the ceramic board. The second resin board is superposed to a second surface of the ceramic board opposite to the first surface of the ceramic board. The second resin board includes a joint pad at its first surface opposite to its second surface facing the ceramic board, the joint pad made of metal. The metal member is joined to the joint pad by brazing or soldering.

Abstract: A variable-speed driving system for 3-phase induction motor by potential-dividing D.C. power from a D.C. power supply into two D.C. powers, converting these two D.C. powers into 3-phase A.C. powers by means of series-connecting 3-phase inverters and delivering the 3-phasse A.C. powers to respective windings of the 3-phase induction motor. In order to equalize the output powers of the series-connected 3-phase inverters, circuits are provided which are operative in accordance with the voltage difference between the voltages input to said 3-phase inverters so as to control the modulation factors of the 3-phase inverters in the variable voltage/variable frequency mode and to control the voltages input to the 3-phase inverters in the constant voltage/variable frequency mode.