Brushless adjustable speed drive

Claim 1

IN A VARIABLE-SPEED DRIVE SYSTEM FOR SUPPLYING POWER FROM A MULTI-PHASE AC POWER LINE TO A MOTOR INCLUDING FIXED ARMATURE WINDINGS AND A FIELD ROTATABLE WITH THE MOTOR SHAFT, THE SYSTEM INCLUDING PLURAL SEMICONDUCTOR CONTROLLED RECTIFIER DEVICES EACH HAVING A CONTROL ELECTRODE TO TRIGGER IT INTO CONDUCTION AND SAID CONTROLLED RECTIFIER DEVICES BEING CONNECTED FROM EACH OF THE PHASES OF THE POWER LINE TO EACH OF THE ARMATURE-WINDINGS IN TWO GROUPS HAVING OPPOSITE POLARITY DIRECTIONS, AND THE SYSTEM FURTHER INCLUDING SHAFT-POSITION SENSING MEANS DELIVERING SEQUENTIAL OUTPUTS DURING ROTATION OF THE SHAFT, IMPROVED MEANS FOR SELECTIVELY TRIGGERING THE CONTROLLED RECTIFIER DEVICES TO PASS POWER-LINE CURRENT THROUGH THE WINDINGS TO MAINTAIN ARMATURE FLUX ROTATING AT A RATE INDEPENDENT OF THE POWER LINE FREQUENCY, COMPRISING: (A) PLURALITY NORMALLY DISABLED FIRING CIRCUIT MEANS EACH CONNECTED TO THE CONTROL ELECTRODE OF AT LEAST ONE RECTIFIER DEVICE AND, WHEN ENABLED, DELIVERING A TRAIN OF TRIGGERING SIGNALS THERETO AT A RATE WHICH IS HIGH AS COMPARED WITH THE POWER LINE FREQUENCY; (B) GATE MEANS CONNECTED TO EACH FIRING CIRCUIT MEANS FOR ENABLING THE LATTER WHEN A FIRST AND SECOND INPUT TO THE GATE MEANS ARE BOTH ENERGIZED; (C) CIRCUIT MEANS CONNECTING EACH SHAFT-POSITION SENSING MEANS OUTPUT TO THE FIRST INPUTS OF ALL OF THE GATE MEANS WHICH ARE ASSOCIATED WITH THE SAME GROUP OF CONTROLLED RECTIFIER DEVICES; (D) PHASE-SENSING MEANS CONNECTED TO THE POWER LINE PHASES AND INCLUDING MEANS FOR DELIVERING SEPARATE OUTPUTS REPRESENTING EACH PHASE WHENEVER IT HAS A PREDETERMINED POLARITY AND AMPLITUDE; AND (C) CIRCUIT MEANS CONNECTING THE SECOND INPUT OF EACH GATE MEANS TO ONE OF SAID PHASE SENSING OUTPUTS.