| 摘要 |
A snubber circuit as a conventional protection circuit for inverters, which is composed of an anode reactor, a Si diode and a resistance, needs to keep junction temperature of the Si diode at 125° C. or lower during operation and therefore requires mounting of a large-size heat sink, which causes a large number of component parts and difficulty in downsizing. As a diode of a snubber circuit for circulating electomagnetic energy of the anode reactor, a wide gap semiconductor (SiC) diode, which does not need a heat sink or requires only a small-size heat sink, is used. When the current density of SiC diode is made 20 to 30 times larger than the current density during normal temperature operation, ON resistance increases, and therefore it becomes possible to substitute the ON resistance for the resistance of the snubber circuit. The increase in current density increases the temperature of the SiC diode. However, since the SiC diode can operate at temperature near 300° C. without any problems, a large-size heat sink is not necessary.
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