Current limit for an electric machine

A method for limiting current and voltage in a PM electric machine comprising:

• receiving a voltage command indicative of a desired position control;
• computing a first voltage threshold for said electric machine based on a selected operating condition;
• and
• if said voltage command exceeds said first voltage threshold, establishing a modified voltage command as substantially equivalent to said first voltage threshold, otherwise establishing a modified voltage command as substantially equivalent to said voltage command;
• computing a second voltage threshold for said electric machine based on another selected operating condition, said second voltage threshold corresponding to a selected minimum voltage for said electric machine at said another selected operating condition;
• and
• if said voltage command is less than said second voltage threshold, establishing said modified voltage command as substantially equivalent to said second voltage threshold, otherwise establishing said modified voltage command as substantially equivalent to said voltage command.

A system for limiting current and voltage in a PM electric machine comprising:

• a PM electric machine;
• a position sensor configured to measure a position of said electric machine and transmit a position signal;
• a controller in operable communication with a voltage source and said electric machine and said position sensor, said controller computing a voltage command responsive to a desired position control;
• wherein if said voltage command exceeds a first voltage threshold, said controller establishes a modified voltage command as substantially equivalent to said first voltage threshold, otherwise said controller establishes a modified voltage command as substantially equivalent to said voltage command, wherein at least one of said voltage command, said first voltage threshold, and said second voltage threshold being based on temperature.

A system for limiting current and voltage in a PM electric machine comprising:

• a PM electric machine;
• a position sensor configured to measure a position of said electric machine and transmit a position signal;
• a controller in operable communication with a voltage source and said electric machine and said position sensor, said controller computing a voltage command responsive to a desired position control;
• wherein if said voltage command exceeds a first voltage threshold, said controller establishes a modified voltage command as substantially equivalent to said first voltage threshold, otherwise said controller establishes a modified voltage command as substantially equivalent to said voltage command;
• and
• if said voltage command is less than a second voltage threshold, said controller establishes said modified voltage command as substantially equivalent to said second voltage threshold, otherwise said controller establishes said modified voltage command as substantially equivalent to said voltage command, said second voltage threshold corresponding to a selected minimum voltage for said electric machine at a first selected operating condition.