Control device for commutatorless motor

Claim 1

An advance angle control apparatus for a commutatorless motor, comprising frequency converter means including a plurality of thyristors for converting a frequency in order to supply an AC power to armature windings of a synchronous motor, a position detector for detecting the position of the rotor of said synchronous motor, a speed detector for detecting an actual speed of said synchronous motor, a speed control means including a first gate pulse generator for controlling the firing phase of said thyristors in accordance with a signal obtained by comparing the actual speed with a command speed, a second gate pulse generator for generating signals controlling the gates of said thyristors in accordance with the output of said position detector, and an advance angle control command circuit applied with the output of said speed detector, for outputting to said second gate pulse generator a signal with a low value for an advance angle at a low speed of said synchronous motor and a high value for the advance angle at a high speed, said advance angle control command circuit comprising a comparator for comparing the actual speed value with a reference value provided by a speed setting circuit, and a change regulating circuit applied with the output of said comparator for regulating a change between advance angle control command signals at the low speed and the high speed during a predetermined time interval, and the output of which is applied to said second gate pulse generator as the advance angle control command signals, said comparator switching its output signal from a constant value to another constant value when the actual speed value reaches a predetermined speed value.