| 摘要 |
PURPOSE:To protect a snubber resistor against burning due to overheating, under continuous operation with a low speed, by limiting temperature rise of the resistor during operation in a speed region exceeding an average switching frequency. CONSTITUTION:Temperature of a snubber resistor may exceeds the maximum allowable level 41, in a speed region exceeding an average switching frequency for which the capacity of the snubber resistor is designed. Temperature of the snubber resistor is monitored continuously by means of a snubber resistor temperature sensor 40 such as a thermocouple, and an inverter is stopped when thus monitored temperature exceeds a maximum allowable temperature 41. A comparator 42 is provided with a hysteresis 43, as required, and the inverter is brought into operable state only after sufficient droppage of the resistor temperature. By such arrangement, the snubber resistor constituting the inverter circuit can be protected against overheat resulting in economical designing of the resistor capacity. |
