BRUSHLESS DC ADJUSTABLE SPEED DRIVE WITH STATIC REGENERATIVE DC MOTOR CONTROL

• US 3,678,358 A
• Filed: 07/14/1970
• Issued: 07/18/1972
• Est. Priority Date: 07/14/1970
• Status: Expired due to Term

• Current Assignee: Edwin E. Kolatorowicz
• Original Assignee: Edwin E. Kolatorowicz
• Inventors: Kolatorowicz, Edwin E.
• Primary Examiner(s): Simmons, G. R.
• Application Number:
  US05/054,703
• Time in Patent Office: 735 Days
• Field of Search: 318/138,254,439,696,685
• US Class Current: 318/400.22
• CPC Class Codes: H02P 6/24 Arrangements for stopping

Abstract

For a brushless direct current motor there is provided a static adjustable speed control circuit including an SCR converter for controlling the average voltage applied to the motor windings by phase control of current flowing directly from a multi-phase power source and for commutating the current through the motor winding to maintain the proper current flow direction and torque. The SCR converter is controlled as a function of rotor position, a-c line input conditions, phase advance and SCR converter voltage output. A voltage feedback signal from the converter output is compared to a reference voltage to derive a comparison signal used to adjust the phase advance and thereby control the average voltage applied to the motor terminals. The polarity of the comparison signal determines whether motoring action or regeneration is to occur. Current feedback from the input lines is used to prevent combinations of SCRs from '"'"''"'"''"'"''"'"'turning on'"'"''"'"''"'"''"'"' and short circuiting the load.

Claims

1. In an adjustable speed drive system including a plurality of controllable rectifiers for coupling a polyphase a-c electric power source and a polyphase motor including a rotor for rotation within and relative to stationary armature windings, rotor position sensing means coupled to the rotor for developing sequential position signals indicative of the angular position and direction of rotation of the rotor, phase-sensing means coupled to the a-c electric power source for generating sequential phase signals each indicating that a respective one of the phases has attained a predetermined polarity and magnitude, improved control means for controlling drive system operation throughout a full reversible range of motoring and regenerative operation, said improved control means comprising:

a command signal source for generating a reference signal having a polarity and magnitude indicative of a desired level of motor performance within a range of permissible performance, a performance signal source coupled to the motor and said command signal source for generating a performance signal having a polarity opposite to that of the reference signal and a magnitude indicative of the actual level of motor performance within the range of permissible performance, the absolute magnitude of the performance signal for any given level of actual performance being substantially equal to the absolute magnitude of the reference signal indicative of said given level of motor performance, first means coupled to the command signal source and the performance signal source and being responsive to a reference signal and a performance signal for generating a comparison signal having a magnitude proportional to the sum of the reference and performance signals, second means coupled to said first means, said command signal source, and said rotor position sensing means for receiving therefrom as input signals the comparison signal, the reference signal, and the position signals for generating in response thereto a first output signal when the input signals are consistent with drive system operation in either the forward motoring mode or the reverse regenerative mode and for generating in response thereto a second output signal when the input signals are consistent with drive system operation in either the forward regenerative mode or the reverse motoring mode, and firing signal generation means coupled to said second means and being responsive to first and second output signals therefrom to generate and supply firing signals to the controllable rectifiers in a first sequence in response to the first output signal and to generate and supply firing signals to the controllable rectifiers in a second sequence in response to the second output signal, said firing signal generation means also being coupled to said first means, said phasesensing means, and said rotor position sensing means for receiving therefrom the comparison signal, the phase signals, and the position signals and being responsive thereto to control the rate of power transfer between the a-c power source and the motor.

2. An adjustable speed drive system as defined by claim 1 further including current sensing means coupled to the a-c power source for generating feedback signals representative in magnItude of the current flow through selected ones of the controllable rectifiers, the feedback signals being coupled to said second means to permit changes in firing signal sequence only when the current flow is at a level at which the change in sequence may be made without damaging changes in current flow.

3. An adjustable speed drive system as defined by claim 2 including, additionally, a reactor having a center-tapped winding per motor armature winding, the center tap of each of the windings being connected to a respective one of the motor armature windings, a first end tap of each center-tapped winding connected to a plurality of controllable rectifiers poled in a first direction and a second end tap of each center-tapped winding connected to a like plurality of controllable rectifiers poled in the opposite direction, the plurality of controllable rectifiers in each instance being equal to the number of phases comprising the a-c electric power source, each reactor winding thereby conducting electric power in a first direction with respect to the motor between the center tap and the first end tap, and in a second direction with respect to the motor between the center tap and the second end tap as governed by the firing of the oppositely poled controllable rectifiers associated therewith and introducing a current limiting impedance between the oppositely poled controllable rectifiers as added protection therefor in the event of a malfunction.