AC motor driving circuit and electric vehicle driving circuit

#This application claims priority to and the benefit of Japanese Patent Application No. 2008-126042, filed May 13, 2008, the disclosure of which is incorporated herein by reference in its entirety.

#1. Field of the Invention

#The invention relates to an AC motor driving circuit for driving an AC motor by using an AC generator and a DC power source including a storage battery and a capacitor, and to an electric vehicle driving circuit using the AC motor driving circuit.

#FIG. 1 is a circuit diagram showing an embodiment of an AC motor driving circuit according to the invention;

#FIG. 2 is a circuit diagram showing a first specific example of the bidirectional switch used in the driving circuit shown in FIG. 1;

#FIG. 3 is a circuit diagram showing a second specific example of the bidirectional switch used in the driving circuit shown in FIG. 1;

#FIG. 1 is a circuit diagram showing an embodiment of an AC motor driving circuit according to the invention.

#As is shown in FIG. 1, in the embodiment, to the output side of a three-phase AC generator 1, a current source rectifier 2 is connected, on the output side of which a first voltage source inverter 3 is provided to be connected thereto through a pair of positive and negative DC input terminals. On the output side of the first voltage source inverter 3, with the three-phase AC output thereof, variable-speed driving of a three-phase AC motor 4 is carried out. To each of the three-phase AC output terminals of the first voltage source inverter 3, one of terminals of a bidirectional switch 6 is connected, the other terminal of which is connected to the positive terminal of a storage battery 5. The negative terminal of the storage battery 5 is connected to the negative DC input terminal of the first voltage source inverter 3. For the storage battery 5, there can be used a capacitor or a DC power source system which is connected to a storage battery or a capacitor through a DC to DC converter such as a DC chopper capable of bidirectional power conversion.

#With the configuration shown in FIG. 1, the electric power conversion between the AC output of the AC generator 1 and the AC input to the AC motor 4 is actualized by once converting the AC output of the AC generator 1 into a DC output with the current source rectifier 2 before converting the DC output into an AC output with the first voltage source inverter 3. Moreover, in FIG. 1, the section surrounded by a dot-dash line is a second voltage source inverter 31 formed with the three bidirectional switches 6 and three lower arms of the first voltage source inverter 3 (one arm is formed with a switching device 3a and a diode 3b connected in inverse parallel therewith). The second voltage source inverter 31 has the output of the storage battery 5 as its DC input and, with its output, carries out variable-speed driving of the AC motor 4.