Microprocessor speed controller

• US 4,843,297 A
• Filed: 09/02/1986
• Issued: 06/27/1989
• Est. Priority Date: 11/13/1984
• Status: Expired due to Fees

• Current Assignee: Unico, Inc.
• Original Assignee: Zycron Systems Incorporated
• Inventors: Ramadei, Michael J., Landino, Paul J.
• Primary Examiner(s): Smith, Jr., David
• Application Number:
  US06/902,501
• Time in Patent Office: 1,029 Days
• Field of Search: 318/806, 318/798, 318/807-811
• US Class Current: 318/811
• CPC Class Codes: H02P 23/0077 Characterised by the use of a particular software algorithm
• CPC Class Codes: H02P 27/08 with pulse width modulation

Abstract

An AC Motor Speed Controller used to control the Speed, Torque and Horsepower of an AC motor. It allows the speed of the motor to be adjusted to the desired level and is calibrated to develop the desired torque, either automatically through load feedback or through a predetermined or preset level. It also allows for excessive torque to be developed under starting and acceleration conditions while providing for controlled deceleration with proportional braking of the inertia load.

Claims

1. In a speed and torque controller for an AC motor having at least one winding and wherein power from a source of high DC voltage power is applied to the winding through power switches whose conduction intervals are controlled by pulse duratoin variable pulses with the power switches coupled to the winding and with the enabling of the power switches being controlled by a square wave whose frequency is representative of a desired speed of the AC motor and with the duration of the variable pulses, during which current is supplied to the winding by the power switches, being representative of a desired output voltage to the winding of the AC motor, the improvement comprising:

means which is DC coupled to said AC motor winding for producing a feedback signal representative of the output voltage to said AC motor winding;

means for producing and storing a plurality of values representative of output voltages as a function of said feedback voltage and producing a feedback signal that is linearized with respect to frequency in response to said feedback voltage;

means responsive to the linearized feedback signal for establishing a desired duration of the duration variable pulses, commensurate with the frequency of the square wave signals and a desired voltage per hertz relationship at the AC motor winding;

means for determining whether the AC motor speed is within a low speed boost region and producing a low speed signal indicative thereof; and

means responsive to the low speed signal for generating a boost signal representative of a desired output voltage to the AC motor winding, said boost signal generating means including means for producing a plurality of look-up tables composed of values for the boost signal at predetermined speed ranges of the AC motor.

2. A speed and torque controller for an AC motor having windings, comprising:

means for producing a source of high DC voltage electrical power across a high voltage buss and a return buss, said DC voltage source being sufficient to derive therefrom an AC power drive for said AC motor windings;

controllable switch means interposed between the busses and the AC motor windings and electrically coupled thereto so as to alternately deliver electrical power in opposite directions through the AC motor windings;

said switch means comprising a first part operatively coupled between the high voltage buss and ends of the windings and a second part operatively coupled between the return buss and ends of the windings, with each part formed of a plurality of switches respectively coupling the high voltage buss to a different end of said windings and coupling the return buss to said same winding ends;

means for generating square wave signals with a frequency commensurtae with a desired speed of the AC motor and with a phase relationship adapted to the phase of the AC motor windings, said square wave signals having equal duration on-segments and off-segments;

first means coupling the square wave signals to switches in the first part of the switch means so as to render said latter switches conductive during the on-segment and non-conductive during the off-segment of the square wave signals in a sequence that is commensurate with the phase of said windings;

means for generating a plurality of equal duration controlled pulses during one-half of respective square wave signals, with the duration of the pulses being commensurate with a desired output voltage to the AC motor windings; and

second means for coupling, in phase with the first coupling means, duration-controlled pulses to those switches in the second part of the switch means to enable current flow through the windings coupled to the high voltage buss by those switches that are rendered conductive by the square wave signals, whereby current is delivered to said AC motor windings and the voltage thereto is regulated by only pulsing a portion of the switch means at the high rate of the duration-controlled pulses;

means, which is DC coupled to ends of the AC motor windings, for producing a feedback signal representative of a combination of the voltages applied to a plurality of output windings by said power switches;

means for producing and storing a plurality of values representative of output voltages as a function of said feedback voltage and producing a feedback signal that is linearized with respect to frequency in response to said feedback voltage;

means responsive to the linearized feedback signal for establishing a desired duration of the duration-controlled pulses, commensurate with the frequency of the square wave signals and a desired voltage per hertz relationship at the AC motor windings;

means for generating a deceleration signal representative of a selected deceleration rate for the AC motor;

means responsive to the deceleration signal for generating a train of pulses whose individual durations are proportional to the selected deceleration rate; and

means responsive to the latter train of pulses for absorbing electrical energy from the high DC voltage buss during deceleration of the AC motor.

3. In a voltage control for an AC motor speed and torque controller having at least one winding to which electrical power is delivered from a high voltage buss and a low voltage buss which are coupled to a high voltage DC power source by power switches that are interposed so as to deliver opposite current flows alternately through the winding, the improvement comprising:

means, which is DC coupled to the winding, for producing a feedback signal representative of the voltage applied to the winding;

means for producing and storing a plurality of values representative of output voltages as a function of said feedback voltage and producing a feedback signal that is linearized with respect to frequency in response to said feedback voltage; and

means responsive to the linearized feedback signal for establishing a desired duration of the duration-controlled pulses, commensurate with the frequency of the square wve signals and a desired voltage per hertz relationship at the AC motor windings.