Control system for an electronically commutated motor

• US 4,449,079 A
• Filed: 08/27/1982
• Issued: 05/15/1984
• Est. Priority Date: 04/17/1980
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Erdman, David M.
• Primary Examiner(s): Rubinson, G. Z.
• Assistant Examiner(s): Moose, Richard M.
• Application Number:
  US06/412,421
• Time in Patent Office: 627 Days
• Field of Search: 318/138, 318/254, 318/331, 318/439, 318/434, 318/311, 318/317
• US Class Current: 318/400.31
• CPC Class Codes: F25B 2600/021 Inverters therefor
• CPC Class Codes: H02P 6/085 in a bridge configuration

Abstract

A circuit for controlling the energization of an electrical load from an AC source. The circuit has a pair of DC lines, and means is provided for rectifying the AC output of the source to apply a DC voltage across the DC lines in the form of a full wave rectified sinusoidal signal. Signal switching means for connection between the DC lines and the load establishes a conductive path therebetween during a variable time interval when the voltage applied by the full wave rectified sinusoidal signal exceeds the voltage across the load, and means including the switching means is provided for chopping the full wave rectified sinusoidal signal to apply pulses to the load during the variable time interval at a frequency which is high with respect to the frequency of the signal. Means connected to the chopping means for modulating the width of the pulses is responsive to an externally derived signal representative of the desired operation of the load, and means is responsive to the load current for modifying the externally derived signal to maintain the amplitude of the load current below a predetermined level whereby a high power factor is presented to the AC source during a predetermined range of operation of the load.

A laundering apparatus, a method of operating a laundry machine, a control system for an electronically commutated motor, and a method of operating an electronically commutated motor are also disclosed.

Claims

1. A system for controlling the energization of an electronically commutated motor having a stationary assembly with a plurality of winding stages and also having a rotatable assembly associated in magnetic coupling relation with the stationary assembly upon the energization of the motor, the system comprising:

means responsive to the angular position of the rotatable assembly for providing commutation signals;

a plurality of commutation switching means for connection with the winding stages, respectively;

means for applying the commutation signals in sequence to said commutation switching means to control the conductivity thereof;

circuit means for dissipating energy generated by the commutation of the winding stages and including a first common point connected to one terminal of each of the winding stages, and first diode means for separate connection between the other terminal of each of the winding stages and a second common point;

said commutation switching means being connected between a third common point and the other terminal of each of the winding stages;

an energy return circuit including capacitor means for connection between said first and second common points;

first impedance means, first transistor means and second diode means for connection in series combination between said first and second common points;

voltage divider means and second transistor means for connection in series combination substantially between said second and third common points, said voltage divider means including second and third impedance means for connection at a fourth common point;

means responsive to the voltage at said fourth common point for controlling the conductivity of said first transistor means;

means for deriving a control signal representative of the actual angular velocity of the rotatable assembly; and

means for applying the control signal to said second transistor means to decrease the conductivity thereof whenever the actual angular velocity of the rotatable assembly exceeds an externally determined variable limit with the decreased conductivity of said secnd transistor means being effective to increase the conductivity of said first transistor means and whereby energy generated upon the commutation of the winding stages is stored in said capacitor means for subsequent dissipation and a negtive torque is variably applied to the rotatable assembly in proportion to the amount by which the actual velocity exceeds the variable limit.

2. A system as set forth in claim 1 further including a fourth impedance means for connection in series combination with said voltage divider means and said second transistor means between said second and third common points.

3. A system as set forth in claim 1 wherein the first transistor means includes a first control terminal, said first control terminal being connected to said fourth common point, whereby the voltage on said first control terminal is governed by the conductivity of said second transistor means.

4. A system as set forth in claim 3 wherein the second transistor means includes a second control terminal, the voltage on said second control terminal controlling the conductivity of said second transistor means and thereby controlling the voltage at said fourth common point, said means for applying the angular velocity control signal being connected to said second transistor means to apply the control signal to said second control terminal.

5. A system for controlling the energization of an electronically commutated motor having a stationary assembly with a plurality of winding stages and also having a rotatable assembly associated in magnetic coupling relation with the stationary assembly upon the energization of the motor, the system comprising:

means responsive to the angular position of the rotatable assembly for providing commutation signals;

a plurality of commutation switching means for connection with the winding stages, respectively;

means for applying the commutation signals in sequence to said commutation switching means to control the conductivity thereof;

circuit means for dissipating energy generated by the commutation of the winding stages, said circuit means being connected to one terminal of each of the winding stages and including a first energy dissipating branch with a first control terminal, the signal on said first control terminal governing the amount of energy dissipated in said first energy dissipating branch, the energy dissipation in said first energy dissipating branch exceeding the energy to be dissipated due to commutation for some range of magnitudes of signals on said first control terminal, whereby when the energy dissipation in said first energy dissipating branch exceeds that dissipation required due to commutation a negative torque is variably applied to the rotatable assembly corresponding to the magnitude of the control signal, and a second energy dissipating branch with a second control terminal, the signal on said second control terminal governing the magnitude of the signal on said first control terminal;

means for deriving a control signal representative of the actual angular velocity of the rotatable assembly; and

means for applying the control signal to said second control terminal to govern the signal on said first control terminal to increase the energy dissipated in said first energy dissipating branch above that required due to commutation whenever the actual angular velocity of the rotatable assembly exceeds a predetermined limit, whereby a negative torque is variably applied to the rotatable assembly in proportion to the amount by which the actual angular velocity exceeds the predetermined limit.

6. A system as set forth in claim 5 wherein said first energy dissipating branch is connected in parallel with the winding stages and includes first transistor means connected in series combination with a first impedance means.

7. A system as set forth in claim 6 wherein said first transistor means includes a base terminal which comprises said first control terminal, the magnitude of the signal on said base terminal determining the amount of energy dissipated in said first impedance means.

8. A system as set forth in claim 6 wherein said second energy dissipating branch includes voltage divider means and a second transistor means, said voltage divider means having second and third impedance means for connection at the first control terminal, and wherein a decrease in the conductivity of said second transistor means is effective to increase the conductivity of said first transistor means so as to increase the energy dissipated in said first impedance means.

9. A system for controlling the energization of an electronically commutated motor having a stationary assembly with a plurality of winding stages and also having a rotatable assembly associated in magnetic coupling relation with the stationary assembly upon the energization of the motor, the system comprising:

means responsive to the angular position of the rotatable assembly for providing commutation signals;

a plurality of commutation switching means for connection with the winding stages, respectively;

means for applying the commutation signals in sequence to said commutation switching means to control the conductivity thereof;

circuit means for dissipating energy generated by the commutation of the winding stges, said circuit means being connected to one terminal of each of the winding stages and including first impedance means and first transistor means for connection in series combination substantially in parallel with the winding stages, said first transistor means having a first control terminal, the magnitude of the signal on said first control terminal determining the amount of energy dissipated in said first impedance means, the energy dissipation in said first impedance means exceeding the energy to be dissipated due to commutation for some range of magnitudes of signal on said first control terminal, whereby when said energy dissipation in said first impedance means exceeds that dissipation required due to commutation a negative torque is variably applied to the rotatable assembly corresponding to the magnitude of the control signal, voltage divider means, and second transistor means, said voltage divider means having second and third impedance means for connection at said first control terminal, a decrease in the conductivity of said second transistor means being effective to increase the conductivity of said first transistor means;

means for deriving a control signal representative of the actual angular velocity of the rotatable assembly; and

means for applying the control signal to said second transistor means to increase the energy dissipated in said first impedance means above that required due to commutation whenever the actual angular velocity of the rotatable assembly exceeds a predetermined limit, whereby a negative torque is variably applied to the rotatable assembly in proportion to the amount by which the actual angular velocity exceeds the predetermined limit.

10. A system for controlling the energization of an electronically commutated motor having a stationary assembly with a plurality of winding stages and also having a rotatable assembly associated in magnetic coupling relation with the stationary assembly upon the energization of the motor, the system comprising:

means responsive to the angular position of the rotatable assembly for providing commutation signals;

a plurality of commutation switching means for connection with the winding stages, respectively;

means for applying the commutation signals in sequence to said commutation switching means to control the conductivity thereof;

circuit means for dissipating energy generated by the commutation of the winding stages, said circuit means being connected to one terminal of each of the winding stages at a first common point, said circuit means including first diode means for separate connection between the other terminal of each of the winding stages and a second common point;

said commutation switching means being connected between a third common point and the other terminal of each of the winding stages;

said circuit means further including an energy return circuit including capacitor means for connection between said first and second common points;

said circuit means including first impedance means and first transistor means for connection in series combination between said first and second common points, said first transistor means having a first control terminal, the voltage on said first control terminal determining the amount of energy dissipated in said first impedance means, the energy dissipation in said first impedance means exceeding the energy to be dissipated due to commutation for some range of voltages on said first control terminal, whereby when the energy dissipation in said first impedance means exceeds that dissipation required due to commutation a negative torque is variably applied to the rotatable assembly corresponding to the voltage of the control signal;

said circuit means also including voltage divider means and second transistor means, said voltage divider means including second and third impedance means for connection at said first control terminal, a decrease in the conductivity of said second transistor means being effective to increase the conductivity of said first transistor means;

means for deriving a control signal representative of the actual angular velocity of the rotatable assembly; and

means for applying the control signal to said second transistor means to decrease the conductivity thereof whenever the actual angular velocity of the rotatable assembly exceeds an externally determined variable limit thereby to increase the conductivity of said first transistor means, whereby energy generated upon commutation of the winding stages is stored in said capacitor means for subsequent dissipation and a negative torque is variably applied to the rotatable assembly in proportion to the amount by which the actual anglular velocity exceeds the variable limit.