Apparatus and method for detection and control of circulating currents in a variable speed DC motor

A motor comprising:

• a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted to be energized in at least one preselected sequence;
• a power supply link for connecting the windings to a power supply, said power supply link including power switching devices for selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly, said power switching devices each having a conducting state and a nonconducting state;
• and
• a current regulation circuit comprising:
• a current sensing circuit for sensing current in the power supply link and for generating an overcurrent signal in response to the sensed current exceeding a peak current reference level;
• a timing circuit for defining periods during which each of the power switching devices may be nonconducting, said timing circuit comprising a current blanking circuit for inhibiting the overcurrent signal during a blanking interval triggered by the energization of the windings;
• and
• a control circuit for controlling the power switching devices so that each of the power switching devices is nonconducting in response to the overcurrent signal whereby the power switching devices are nonconducting during the defined periods except during the blanking interval.

A motor comprising:

• a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted to be energized in at least one preselected sequence;
• a power supply link for connecting the windings to a power supply, said power supply link including power switching devices for selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly, said power switching devices each having a conducting state and a nonconducting state;
• and
• a current sensing circuit for sensing current in the power supply link;
• a current blanking circuit for inhibiting the sensed current for a blanking interval triggered by the energization of the windings;
• and
• a control circuit for defining a first period during which each of the power switching devices may be nonconducting and for controlling the power switching devices so that each of the power switching devices is nonconducting when the sensed current exceeds a peak current reference level during the first period except during the predetermined blanking interval whereby current which circulates during periods when only one power switching device is conducting is reduced.

A motor comprising:

• a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted to be energized in at least one preselected sequence;
• a power supply link for connecting the windings to a power supply, said power supply link including power switching devices for selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly, said power switching devices each having a conducting state and a nonconducting state and comprising an inverter bridge, said inverter bridge having a positive rail and a negative rail supplied by the power supply;
• a pulse width modulation circuit for pulse width modulating the power being provided to at least one of the windings at a duty cycle having alternating on and off periods;
• a counter circuit for counting a predetermined number of off periods;
• a current sensing circuit for sensing current in one of the rails of the power supply link;
• and
• a current regulation circuit for controlling the power switching devices so that each of the power switching devices is nonconducting in response to the sensed current exceeding a first peak current reference level only after the predetermined number of off periods is counted whereby current which circulates during periods when only one power switching device is conducting is periodically reduced.

A motor comprising:

• a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted to be energized in at least one preselected sequence;
• a power supply link for connecting the windings to a power supply, said power supply link including power switching devices for selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly, said power switching devices each having a conducting state and a nonconducting state;
• a pulse width modulation circuit for pulse width modulating the power being provided to at least one of the windings at a duty cycle having alternating on and off periods;
• a current sensing circuit for sensing current in the power supply link and for generating an overcurrent signal in response to the sensed current exceeding a peak current reference level;
• a control circuit for defining a period during which each of the power switching devices may be nonconducting;
• a current sensing circuit for sensing current in the power supply link and for generating an overcurrent signal in response to the sensed current exceeding a peak current reference level, said control circuit including a current blanking circuit for inhibiting the overcurrent signal during a blanking interval triggered by the energization of the windings;
• and
• a current regulation circuit for controlling the power switching devices so that each of the power switching devices is nonconducting in response to the overcurrent signal during the defined period except during the blanking interval and after a predetermined number of off periods whereby current which circulates during periods when only one power switching device is conducting is periodically reduced.

A method of operating a system for driving a rotatable component, said system comprising a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted for energization in at least one preselected sequence, said rotatable assembly in driving relation to the rotatable component, said motor also having a power supply link for connecting the windings to a power supply, said power supply link including power switching devices each having a conducting state and a nonconducting state, said method comprising the steps of:

• selectively energizing the windings in the preselected sequence by connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly;
• sensing current in the power supply link;
• generating an overcurrent signal in response to the sensed current exceeding a peak current reference level;
• inhibiting the overcurrent signal during a blanking interval triggered by the energization of the windings;
• regulating current by defining periods during which each of the power switching devices may be nonconducting;
• and
• controlling the power switching devices so that each of the power switching devices is nonconducting in response to the overcurrent signal whereby the power switching device are nonconducting during the defined periods except during the blanking interval.

A system comprising:

• a rotatable component;
• a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted to be energized in at least one preselected sequence, said rotatable assembly being in driving relation to the rotatable component;
• a power supply link for connecting the windings to a power supply, said power supply link including power switching devices for selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly, said power switching devices each having a conducting state and a nonconducting state and comprising an inverter bridge, said inverter bridge having a positive rail and a negative rail supplied by the power supply;
• and
• a current regulation circuit including a timing circuit for defining periods during which each of the power switching devices may be nonconducting, a current sensing circuit for sensing current in only one of the rails of the power supply link and a control circuit for controlling the power switching devices so that each of the power switching devices is nonconducting only during portions of the defined periods during which the sensed current exceeds a peak current reference level.

An application specific integrated circuit (ASIC) for use with a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted for energization in at least one preselected sequence, said motor further having a power supply link for connecting the windings to a power supply, said power supply link including power switching devices for selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly, said power switching devices each having a conducting state and a nonconducting state and comprising an inverter bridge, said inverter bridge having a positive rail and a negative rail supplied by the power supply, said ASIC comprising:

• a timing circuit for defining periods during which each of the power switching devices may be nonconducting;
• a circuit for sensing current in only one of the rails of the power supply link;
• and
• a control circuit for controlling the power switching devices so that each of the power switching devices is nonconducting only during portions of the defined periods during which the sensed current exceeds a peak current reference level.

A current regulation circuit for controlling excessive circulating currents in a power supply link of a motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted for energization in at least one preselected sequence, said power supply link connecting the windings to a power supply and including power switching devices for selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly, said power switching devices each having a conducting state and a nonconducting state and comprising an inverter bridge, said inverter bridge having a positive rail and a negative rail supplied by the power supply, said current regulation circuit comprising:

• a timing circuit for defining periods during which each of the power switching devices may be nonconducting;
• a circuit for sensing current in only one of the rails of the power supply link;
• and
• a control circuit for controlling the power switching devices so that each of the power switching devices is nonconducting only during portions of the defined periods during which the sensed current exceeds a peak current reference level whereby current which circulates during periods when only one power switching device is conducting is reduced.

A method of operating a motor, said motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted for energization in at least one preselected sequence, said motor also having a power supply link for connecting the windings to a power supply, said power supply link including power switching devices each having a conducting state and a nonconducting state and comprising an inverter bridge, said inverter bridge having a positive rail and a negative rail supplied by the power supply, said method comprising the steps of:

• selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly;
• regulating current by defining periods during which each of the power switching devices may be nonconducting;
• sensing current in only one of the rails of the power supply link;
• and
• controlling the power switching devices so that each of the power switching devices is nonconducting only during portions of the defined periods during which the sensed current exceeds a peak current reference level.

A method of operating a motor, said motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted for energization in at least one preselected sequence, said motor also having a power supply link for connecting the windings to a power supply, said power supply link including power switching devices each having a conducting state and a nonconducting state, said method comprising the steps of:

• selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly;
• sensing current in the power supply link;
• inhibiting the sensed current for a blanking interval triggered by the energization of the windings;
• defining a period during which each of the power switching devices may be nonconducting;
• and
• controlling the power switching devices so that each of the power switching devices is nonconducting when the sensed current exceeds a peak current reference level during the defined period except during the blanking interval whereby current which circulates during periods when only one power switching device is conducting is reduced.

A method of operating a motor, said motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted for energization in at least one preselected sequence, said motor also having a power supply link for connecting the windings to a power supply, said power supply link including power switching devices each having a conducting state and a nonconducting state and comprising an inverter bridge, said inverter bridge having a positive rail and a negative rail supplied by the power supply, said method comprising the steps of:

• selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly;
• pulse width modulating the power being provided to at least one of the windings at a duty cycle having alternating on and off periods;
• counting a predetermined number of off periods;
• sensing current in one of the rails of the power supply link;
• and
• controlling the power switching devices so that each of the power switching devices is nonconducting in response to the sensed current exceeding a peak current reference level only after the predetermined number of off periods is counted whereby current which circulates during periods when only one power switching device is conducting is periodically reduced.

A method of operating a motor, said motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted for energization in at least one preselected sequence, said motor also having a power supply link for connecting the windings to a power supply, said power supply link including power switching devices each having a conducting state and a nonconducting state and comprising an inverter bridge, said inverter bridge having a positive rail and a negative rail supplied by the power supply, said method comprising the steps of:

• selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly;
• defining by an application specific integrated circuit periods during which each of the power switching devices may be nonconducting;
• sensing current in only one of the rails of the power supply link;
• and
• controlling the power switching devices so that each of the power switching devices is nonconducting only during portions of the defined periods during which the sensed current exceeds a peak current reference level.

A method of regulating current for controlling excessive circulating currents in a power supply link of a motor, said motor having a stationary assembly and a rotatable assembly in magnetic coupling relation thereto, said stationary assembly including windings adapted for energization in at least one preselected sequence, said power supply link connecting the windings to a power supply and including power switching devices for selectively energizing the windings in the preselected sequence by selectively connecting the power supply link to the windings to produce an electromagnetic field for rotating the rotatable assembly, said power switching devices each having a conducting state and a nonconducting state and comprising an inverter bridge, said inverter bridge having a positive rail and a negative rail supplied by the power supply, said method comprising the steps of:

• defining periods during which each of the power switching devices may be nonconducting;
• sensing current in only one of the rails of the power supply link;
• and
• controlling the power switching devices so that each of the power switching devices is nonconducting only during portions of the defined periods during which the sensed current exceeds a peak current reference level whereby current which circulates during periods when only one power switching device is conducting is reduced.