초록 ▼

For starting a rotatable 3-phase a-c electrical machine of the synchronous type, the stator windings of the machine are connected to an electric storage battery via a controllable electric power converter, and the d-c field winding is connected in series with the stator windings by inserting it in t

For starting a rotatable 3-phase a-c electrical machine of the synchronous type, the stator windings of the machine are connected to an electric storage battery via a controllable electric power converter, and the d-c field winding is connected in series with the stator windings by inserting it in the load current path between the converter and battery. Field weakening resistance is connected in parallel with the field winding. The converter includes a plurality of electric valves (thyristors) that are cyclically turned on in a predetermined sequence in synchronism with alternating voltages developed at the line terminals of the stator windings.

대표청구항 ▼

In a system for starting a rotatable a-c electrical machine of the synchronous type having a stator, a rotor adapted to be coupled to a mechanical load, a set of 3-phase a-c windings on said stator, and a d-c field winding on said rotor, the improvement comprising: a. an electric storage battery; b.

In a system for starting a rotatable a-c electrical machine of the synchronous type having a stator, a rotor adapted to be coupled to a mechanical load, a set of 3-phase a-c windings on said stator, and a d-c field winding on said rotor, the improvement comprising: a. an electric storage battery; b. an electric power converter having a pair of d-c terminals and three a-c terminals which are respectively connected to different phases of said stator windings; c. means for providing a path for load current between said d-c terminals and said battery; d. connecting means for inserting said field winding in said load current path while the rotor of said machine is at rest, said connecting means being effective when said rotor is rotating faster than a predetermined rate for disconnecting said field winding from said path and for reconnecting it to a different source of excitation; e. control means associated with said converter and operative in a “cranking”mode to cause said converter to supply said stator windings with alternating current which tends to increase in frequency and decrease in magnitude as said rotor accelerates from rest, said cranking mode of operat1on commencing on command and concluding in response to rotor speed attaining said predetermined rate; f. resistance means connected in parallel circuit relationship with said field winding in said load current path, the ohmic value of said resistance means having a predetermined initial magnitude; and g. means for reducing the ohmic value of said resistance means to a lower magnitude on command.