Systems and methods for driving a compressor with a motor

Claim 1

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF) in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; a control circuit responsive to the BEMF signal for generating a commutation signal, the control circuit including a commutation counter counting at a rate, the commutation counter incrementing its count when the BEMF signal is of the first polarity and decrementing its count when the BEMF signal is of the second polarity, and generating a corresponding commutation signal when the count reaches a commutation delay value; and power switching devices responsive to the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly.

Claim 2

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF) in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; a control circuit responsive to the BEMF signal for generating a commutation signal, the control circuit including a commutation counter counting at a rate, the commutation counter incrementing its count when the BEMF signal is of the first polarity and decrementing its count when the BEMF signal is of the second polarity, and generating a corresponding commutation signal when the count reaches a commutation delay value; and power switching devices responsive to the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly.

Claim 13

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF) in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; a control circuit response to the BEMF signal for generating a commutation signal, the control circuit including a commutation counter counting at a rate, the commutation counter increasing its count when the BEMF signal is of the first polarity and decreasing its count when the BEMF signal is of the second polarity, and generating a corresponding commutation signal when the count reaches a commutation delay value, the commutation signal including a series of commutation pulses and the control circuit measuring an interval between commutation pulses; power switching devices responsive to the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly; a speed regulation circuit for comparing the measured interval to a reference interval, the reference interval corresponding to a desired motor speed, and for generating a difference signal between the compared measured interval and the reference interval defining a speed errors, and a processor for integrating the speed error and for generating an integrated speed error signal in response thereto, the processor including a speed error precounter for accumulating the speed error and altering the integrated speed error signal when the speed error accumulates to, an amount selected from a predefined set of values, the speed regulation circuit including a speed regulation counter responsive to the integrated speed error signal and the difference signal for generating a peak current reference signal, and the speed regulation circuit regulating the current in the windings as a function of the peak current reference signal thereby to regulate the speed of the motor.

Claim 14

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF) in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; a control circuit response to the BEMF signal for generating a commutation signal, the control circuit including a commutation counter counting at a rate, the commutation counter increasing its count when the BEMF signal is of the first polarity and decreasing its count when the BEMF signal is of the second polarity, and generating a corresponding commutation signal when the count reaches a commutation delay value, the commutation signal including a series of commutation pulses and the control circuit measuring an interval between commutation pulses; power switching devices responsive to the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly; a speed regulation circuit for comparing the measured interval to a reference interval, the reference interval corresponding to a desired motor speed, and for generating a difference signal between the compared measured interval and the reference interval defining a speed errors, and a processor for integrating the speed error and for generating an integrated speed error signal in response thereto, the processor including a speed error precounter for accumulating the speed error and altering the integrated speed error signal when the speed error accumulates to, an amount selected from a predefined set of values, the speed regulation circuit including a speed regulation counter responsive to the integrated speed error signal and the difference signal for generating a peak current reference signal, and the speed regulation circuit regulating the current in the windings as a function of the peak current reference signal thereby to regulate the speed of the motor.

Claim 17

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto the stationary assembly including windings adapted to be energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; a control circuit responsive to the BEMF signal for generating a commutation signal the control circuit including a commutation counter counting at a rate, the commutation counter increasing its count when the BEMF signal is of the first polarity and decreasing its count when the BEMF signal is of the second polarity, and generating a corresponding commutation signal when the count reaches a commutation delay value; power switching devices responsive to the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly; a microcomputer in serial communication with the control circuit: and a microcomputer watchdog circuit for resetting the microcomputer when a data signal from the microcomputer is absent for a predetermined interval of time, the microcomputer watchdog circuit generating a reset signal having a predetermined duration for resetting the microcomputer.

Claim 18

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto the stationary assembly including windings adapted to be energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; a control circuit responsive to the BEMF signal for generating a commutation signal the control circuit including a commutation counter counting at a rate, the commutation counter increasing its count when the BEMF signal is of the first polarity and decreasing its count when the BEMF signal is of the second polarity, and generating a corresponding commutation signal when the count reaches a commutation delay value; power switching devices responsive to the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly; a microcomputer in serial communication with the control circuit: and a microcomputer watchdog circuit for resetting the microcomputer when a data signal from the microcomputer is absent for a predetermined interval of time, the microcomputer watchdog circuit generating a reset signal having a predetermined duration for resetting the microcomputer.

Claim 19

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF) in the windings, said windings having an inductive current producing a field collapse voltage in advance of the back EMF; a control circuit responsive to the BEMF signal for generating a commutation signal; power switching devices responsive to the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly; and a circuit for inhibiting switching events of the power switching devices in advance of the back EMF during periods when the field collapse voltage is present whereby switching events during field collapse voltage are inhibited when the motor is operating below approximately 1/2 no load speed.

Claim 20

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF) in the windings, said windings having an inductive current producing a field collapse voltage in advance of the back EMF; a control circuit responsive to the BEMF signal for generating a commutation signal; power switching devices responsive to the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly; and a circuit for inhibiting switching events of the power switching devices in advance of the back EMF during periods when the field collapse voltage is present whereby switching events during field collapse voltage are inhibited when the motor is operating below approximately 1/2 no load speed.

Claim 21

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF) in the windings; a control circuit responsive to the BEMF signal for generating a commutation signal having a series of commutation pulses and for measuring an interval between commutation pulses; power switching devices responsive to the commutation pulses of the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly; a speed regulation circuit for comparing the measured interval to a reference interval, the reference interval corresponding to a desired motor speed, and for generating a difference signal between the compared measured interval and the reference interval defining a speed error; a processor for integrating the speed error and for generating an integrated speed error signal in response thereto, the processor including a speed error pre-counter for accumulating the speed error and altering the integrated speed error signal when the speed error accumulates to an amount selected from a predefined set of values; and wherein the speed regulation circuit includes a speed regulation counter responsive to the integrated speed error signal and the difference signal for generating a peak current reference signal, and wherein the speed regulation circuit regulates the current in the windings as a function of the peak current reference signal thereby to regulate the speed of the motor.

Claim 22

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF) in the windings; a control circuit responsive to the BEMF signal for generating a commutation signal having a series of commutation pulses and for measuring an interval between commutation pulses; power switching devices responsive to the commutation pulses of the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly; a speed regulation circuit for comparing the measured interval to a reference interval, the reference interval corresponding to a desired motor speed, and for generating a difference signal between the compared measured interval and the reference interval defining a speed error; a processor for integrating the speed error and for generating an integrated speed error signal in response thereto, the processor including a speed error pre-counter for accumulating the speed error and altering the integrated speed error signal when the speed error accumulates to an amount selected from a predefined set of values; and wherein the speed regulation circuit includes a speed regulation counter responsive to the integrated speed error signal and the difference signal for generating a peak current reference signal, and wherein the speed regulation circuit regulates the current in the windings as a function of the peak current reference signal thereby to regulate the speed of the motor.

Claim 23

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF) in the windings; a control circuit responsive to the BEMF signal for generating a commutation signal having a series of commutation pulses and for measuring a commutation interval between consecutive commutation pulses; power switching devices responsive to the commutation pulses of the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly; a current detector circuit for sensing current in each of the windings; and a variable off time circuit for discontinuing for a predetermined period of time power being provided to each of the windings in which the current reaches a peak current reference level for regulating current in the motor, the predetermined period of time selected from a predefined set of values as a function of the measured commutation interval for minimizing losses and for providing smooth torque production.

Claim 24

A system for driving a rotatable component comprising: a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component; a circuit for generating a BEMF signal representative of a back electromotive force (EMF) in the windings; a control circuit responsive to the BEMF signal for generating a commutation signal having a series of commutation pulses and for measuring a commutation interval between consecutive commutation pulses; power switching devices responsive to the commutation pulses of the commutation signal for selectively connecting a power supply to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly; a current detector circuit for sensing current in each of the windings; and a variable off time circuit for discontinuing for a predetermined period of time power being provided to each of the windings in which the current reaches a peak current reference level for regulating current in the motor, the predetermined period of time selected from a predefined set of values as a function of the measured commutation interval for minimizing losses and for providing smooth torque production.

Claim 31

A method of operating a system for driving a rotatable component, the system comprising a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; generating a commutation signal in response to the BEMF signal; increasing a count of a commutation counter counting at a rate when the BEMF signal is of the first polarity and decreasing the count when the BEMF signal is of the second polarity; generating a corresponding commutation signal when the count reaches a commutation delay value; and selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly.

Claim 32

A method of operating a system for driving a rotatable component, the system comprising a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; generating a commutation signal in response to the BEMF signal; increasing a count of a commutation counter counting at a rate when the BEMF signal is of the first polarity and decreasing the count when the BEMF signal is of the second polarity; generating a corresponding commutation signal when the count reaches a commutation delay value; and selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly.

Claim 47

A method of operating a system for driving a rotatable component, the system comprising a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings, said windings having an inductive current producing a field collapse voltage in advance of the back EMF; generating a commutation signal in response to the BEMF signal; selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly; and inhibiting switching events of the power switching devices in advance of the back EMF during periods when the field collapse voltage is present whereby switching events during field collapse voltage are inhibited when the motor is operating below approximately 1/2 no load speed.

Claim 48

A method of operating a system for driving a rotatable component, the system comprising a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings, said windings having an inductive current producing a field collapse voltage in advance of the back EMF; generating a commutation signal in response to the BEMF signal; selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly; and inhibiting switching events of the power switching devices in advance of the back EMF during periods when the field collapse voltage is present whereby switching events during field collapse voltage are inhibited when the motor is operating below approximately 1/2 no load speed.

Claim 49

A method of operating a system for driving a rotatable component, the system comprising a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings; generating a commutation signal in response to the BEMF signal, the commutation signal including a series of commutation pulses; measuring an interval between commutation pulses; selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly; comparing the measured interval to a reference interval, the reference interval corresponding to a desired motor speed; generating a difference signal between the compared measured interval and the reference interval defining a speed error; integrating the speed error and generating an integrated speed error signal in response thereto; accumulating the speed error; altering the integrated speed error signal when the speed error accumulates to an amount selected from a predefined set of values; and generating a peak current reference signal responsive to the integrated speed error signal and the difference signal, and wherein the current in the windings is regulated as a function of the peak current reference signal thereby to regulate the speed of the motor.

Claim 50

A method of operating a system for driving a rotatable component, the system comprising a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings; generating a commutation signal in response to the BEMF signal, the commutation signal including a series of commutation pulses; measuring an interval between commutation pulses; selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly; comparing the measured interval to a reference interval, the reference interval corresponding to a desired motor speed; generating a difference signal between the compared measured interval and the reference interval defining a speed error; integrating the speed error and generating an integrated speed error signal in response thereto; accumulating the speed error; altering the integrated speed error signal when the speed error accumulates to an amount selected from a predefined set of values; and generating a peak current reference signal responsive to the integrated speed error signal and the difference signal, and wherein the current in the windings is regulated as a function of the peak current reference signal thereby to regulate the speed of the motor.

Claim 51

A method of operating a system for driving a rotatable component, the system comprising a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings; generating a commutation signal in response to the BEMF signal, the commutation signal including a series of commutation pulses; measuring a commutation interval between consecutive commutation pulses; selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly; sensing current in each of the windings; and discontinuing for a predetermined period of time power being provided to each of the windings in which the current reaches a peak current reference level to regulate current in the motor, the predetermined period of time selected from a predefined set of values as a function of the measured commutation interval for minimizing losses and for providing smooth torque production.

Claim 52

A method of operating a system for driving a rotatable component, the system comprising a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the rotatable component, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings; generating a commutation signal in response to the BEMF signal, the commutation signal including a series of commutation pulses; measuring a commutation interval between consecutive commutation pulses; selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly; sensing current in each of the windings; and discontinuing for a predetermined period of time power being provided to each of the windings in which the current reaches a peak current reference level to regulate current in the motor, the predetermined period of time selected from a predefined set of values as a function of the measured commutation interval for minimizing losses and for providing smooth torque production.

Claim 53

A method of operating a refrigeration system having a compressor for circulating a refrigerant through an evaporator and a motor for driving the compressor, the motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the compressor, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; generating a commutation signal in response to the BEMF signal; increasing a count of a conmutation counter counting at a rate when the BEMF signal is of the first polarity and decreasing the count when the BEMF signal is of the second polarity; generating a corresponding commutation signal when the count reaches a commutation delay value; and selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly.

Claim 54

A method of operating a refrigeration system having a compressor for circulating a refrigerant through an evaporator and a motor for driving the compressor, the motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the rotatable assembly being in driving relation to the compressor, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; generating a commutation signal in response to the BEMF signal; increasing a count of a conmutation counter counting at a rate when the BEMF signal is of the first polarity and decreasing the count when the BEMF signal is of the second polarity; generating a corresponding commutation signal when the count reaches a commutation delay value; and selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly.

Claim 55

A method of operating a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; generating a commutation signal in response to the BEMF signal; increasing a count of a commutation counter counting at a rate when the BEMF signal is of the first polarity and decreasing the count when the BEMF signal is of the second polarity; generating a corresponding commutation signal when the count reaches a commutation delay value; and selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly.

Claim 56

A method of operating a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings, the BEMF signal having first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the back EMF, the first polarity being representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity being opposite the first polarity; generating a commutation signal in response to the BEMF signal; increasing a count of a commutation counter counting at a rate when the BEMF signal is of the first polarity and decreasing the count when the BEMF signal is of the second polarity; generating a corresponding commutation signal when the count reaches a commutation delay value; and selectively connecting a power supply to the windings in the preselected sequence by switching power switching devices in response to the commutation signal to produce an electromagnetic field for rotating the rotatable assembly.

Claim 57

A method of operating a refrigeration system having a compressor for circulating a refrigerant through an evaporator and a motor for driving the compressor, the motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence during operation of the compressor, the rotatable assembly being in driving relation to the compressor, said system including a refrigerant that is in a gaseous state during compressor operation and that may be in a liquid state during periods when the compressor is not being operated, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings with a back EMF circuit; disabling the back EMF circuit and generating a sump heat signal; generating first and second commutation signals in response to the sump heat signal and the BEMF signal, respectively, the first commutation signal having a commutation rate corresponding to a motor speed exceeding that at which inertia of the rotatable assembly permits rotation; and supplying electrical energy to at least part of the motor windings in response to the first commutation signal so that heat is generated within such part of the motor windings and so that the rotatable assembly is not caused to commence rotation for a period of time sufficient to cause liquid refrigerant in the compressor to change state to a gaseous state; and thereafter supplying electrical energy to the motor windings in the preselected sequence in response to the second commutation signal thereby causing the rotatable assembly to commence rotation with respect to the stationary assembly.

Claim 58

A method of operating a refrigeration system having a compressor for circulating a refrigerant through an evaporator and a motor for driving the compressor, the motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, the stationary assembly including windings selectively energized in at least one preselected sequence during operation of the compressor, the rotatable assembly being in driving relation to the compressor, said system including a refrigerant that is in a gaseous state during compressor operation and that may be in a liquid state during periods when the compressor is not being operated, the method comprising: generating a BEMF signal representative of a back electromotive force (EMF) in the windings with a back EMF circuit; disabling the back EMF circuit and generating a sump heat signal; generating first and second commutation signals in response to the sump heat signal and the BEMF signal, respectively, the first commutation signal having a commutation rate corresponding to a motor speed exceeding that at which inertia of the rotatable assembly permits rotation; and supplying electrical energy to at least part of the motor windings in response to the first commutation signal so that heat is generated within such part of the motor windings and so that the rotatable assembly is not caused to commence rotation for a period of time sufficient to cause liquid refrigerant in the compressor to change state to a gaseous state; and thereafter supplying electrical energy to the motor windings in the preselected sequence in response to the second commutation signal thereby causing the rotatable assembly to commence rotation with respect to the stationary assembly.