| 摘要 |
PROBLEM TO BE SOLVED: To remove an excessive current spike from a first switch by controlling as functions of detected regenerative operation and motor speed a duration for which the closed first switch is temporarily opened and a specified length of delay when the first switch is opened for a specified time after the specified delay following a time at which a second switch is opened. SOLUTION: A comparator 50 compares the polarity of a speed error and that of a speed feedback signal, and feeds its output to an AND gate 55. A device 58 feeds an output signal to the AND gate 55 only when the actual feedback speed of a rotor exceeds the threshold speed. The AND gate 55 provides an adjustable pulse generator 56 with its output signal, and the adjustable pulse generator is also fed with a feedback speed signal from the rotor. A pulse generator 56 provides a switching logic circuit 48 with an appropriate signal representing a command to temporarily open one of the switches on the upper row for a specified duration after a specified time following the start of pulse. |
