| 摘要 |
PROBLEM TO BE SOLVED: To suppress the element loss of an inverter in case that the operation time of the inverter has passed a specified time or more, in each region of dipolar modulation, partial bipolar modulation, and unipolar modulation excluding one pulse modulation. SOLUTION: This controller is provided with an up/down counter part, a time delay part, and a sampling convertor part, and in each modulation region excluding one pulse modulation, this performs up-counting at operation of the inverter, and performs down-counting when the count value comes to a specified detection level or over, and also sets a switching frequency drop detection signal having a time delay of the time until the count value becoming zero, and lowers the switching frequency of the inverter to a specified value by this detection signal. At the same time, this returns the switching frequency to the initial value when this detection signal is cleared, using this detection signal as the trigger of the down count action of the counter part. |
