| 摘要 |
<p>PURPOSE:To smooth change-over by a mechanism wherein thyristors ON-OFF controlled taking time lag at a half-period of an AC power source are operated after a discriminator deciding the saturation of a thyristor, whose phase is controlled, generates output. CONSTITUTION:When a motor M is driven by means of a thyristor device Th1, whose phase is controlled, and thyristor devices Th2, Th3 ON-OFF controlled, the lapping of the reference pulses of a reference pulse generating circuit BP and output from a phase shifter PS is detected by means of a comparator CD, and the reaching of the output from the phase shifter PS to the maximum flow rate is memorized to a memory circuit alphaM. The memorized output is added to an ON-OFF instruction circuit CE, and the thyristor device Th1 is closed through the phase shifter PS while the thyristor devices Th2, Th3 ON-OFF controlled are worked through delay circuits TD1, TD2. Thus, overshoot, etc. in case of change-over can be eliminated, and the transient variation of the currents of the motor can be prevented.</p> |
