| 摘要 |
<p>The invention relates to a power conversion device including an inverter which converts a voltage of a direct current power source 2 to an alternating current voltage of any magnitude and frequency using semiconductor switches 4, and supplies the voltage to a load such as an electric motor 5, wherein a switch unit 3 is provided in the direct current portion of the inverter. In the invention, a capacitor 1 is connected, via the switch unit 3, between a positive electrode and a negative electrode of the direct current power source 2, and a constant voltage element wherein when a fixed voltage or higher is reached, an electrical resistance decreases abruptly, current flows, and voltages between both ends are limited to specific voltage, is connected in parallel to the capacitor 1. Herein, a varistor 6, a zener diode 7, or an avalanche diode is used, or alternatively, a combination of the zener diode 7 and a self-turn-off semiconductor element (an IGBT, a MOSFET, or the like), or the like, is used, as the constant voltage element. Owing to the heretofore described configuration, each part configuring the power conversion device is protected against overvoltage, thus avoiding an increase in the capacitance and volume of the capacitor 1.</p> |
