| 摘要 |
PURPOSE:To prevent an erroneous detection of an overload state of a motor by detecting only a ripple of the motor from a pulse of a reverse phase corresponding to a variation amount of a power source voltage only during a period when the variation amount of the power source voltage exceeds a set value, in addition to a waveform corresponding to a motor current. CONSTITUTION:When a substantially periodical voltage variation exceeding a set value occurs in a battery at the time of driving a motor M, switching means SM1 is closed by an output pulse from a comparator, extended for a predetermined time by time holding means 44. Then, the pulse is input to a band pass amplifier 46 as remaining in a reverse phase, combined with a ripple waveform of the motor, superposed with the voltage variation to cancel the voltage variation, and only the ripple is detected and monitored by ripple detecting means 40. Then, when the motor M is restricted, an overload detection signal from the means 40 is output to a central processing unit 16, and a predetermined safety operation is executed. Thus, an erroneous detection of presence or absence of the ripple can be prevented. |
