Dynamic current limiting

In a system issuing commands for current, the improvement comprising:

• dynamically determining a first level of current that will not overheat a first component;
• dynamically determining a second level of current that will not overheat a second component;
• and
• preventing the commands from requesting current in excess of any of the first and second dynamically determined levels.

In a system issuing commands for motor current in a motor, the improvement comprising:

• dynamically determining a first limit as a function of measured motor current and as a function of a measured temperature proximate the motor;
• dynamically determining a second limit as a function of measured transistor current and as a function of measured temperature proximate the transistor;
• and
• preventing the commands for current from exceeding any of the first and second dynamically determined limits.

A computer program product for use in controlling commands for motor current, the computer program product comprising a computer usable medium having computer readable code thereon, the computer readable program code including:

• program code for dynamically determining a first limit as a function of estimated temperature of a motor winding;
• program code for dynamically determining a second limit as a function of estimated temperature of a power transistor;
• and
• program code for preventing the commands for motor current from exceeding any of the first and second dynamically determined limits.

A computer program product for use in controlling commands for motor current, the computer program product comprising a computer usable medium having computer readable code thereon, the computer readable program code including:

• program code for dynamically determining a first limit as a function of measured motor current and as a function of a measured temperature proximate the motor;
• program code for dynamically determining a second limit as a function of measured transistor current and as a function of measured temperature proximate the transistor;
• and
• program code for preventing the commands for current from exceeding any of the first and second dynamically determined limits.

A control circuit for a motor comprising:

• motor windings;
• at least three power transistors providing current to said motor windings;
• a current sensor measuring at least one motor current;
• a temperature sensor measuring temperature of a heat sink in proximity to the motor;
• a processor responsive to the measured current and the measured temperature to calculate estimated temperature of the one of the at least three power switches, said processor further calculating estimated temperature of the motor winding and dynamically determining a current command limit as a function of estimated power switch temperature, a second current command limit as a function of estimated motor winding temperature and a lowest limit from among the first current command limit, the second current command limit and a fixed limit;
• and
• limiting current commands to said motor to no more than the dynamically determined lowest limit.

A control circuit for a motor comprising:

• motor windings;
• at least three power transistors providing current to said motor windings;
• a current sensor measuring at least one power transistor current;
• a temperature sensor measuring temperature of a heat sink near at least one of the power transistors;
• a processor responsive to the measured current and the measured temperature to calculate estimated temperature of the one of the at least three power switches, said processor further calculating estimated temperature of the motor winding and dynamically determining a current command limit as a function of estimated power switch temperature, a second current command limit as a function of estimated motor winding temperature and a lowest limit from among the first current command limit, the second current command limit and a fixed limit;
• and
• limiting current commands to said motor to no more than the dynamically determined lowest limit.