Torque current comparison for current reasonableness diagnostics in a permanent magnet electric machine

A diagnostics system for ascertaining status of an electric machine, the system comprising:

• said electric machine coupled to a polyphase bus, including a position encoder coupled to said electric machine to detect rotational position;
• an inverter having an input coupled to a direct current bus, and an output coupled to said polyphase bus, responsive to commands from a controller;
• said controller coupled to said inverter and to said position encoder;
• a sensor to detect a current from said direct current bus;
• said controller capturing a torque current;
• said controller calculating a current error
• said controller establishing a bound limit for said torque current;
• said controller comparing said current error value to said bound limit;
• said controller determining whether a fault exists by evaluating if said bound limit has been exceeded and generating a current error;
• said controller incrementing a fault counter by a first predetermined count if said fault exists;
• said controller decrementing said fault counter by a second predetermined count if no fault exists;
• said controller providing a fault indication to declare a failure if said fault counter exceeds a predeterrnined limit.

A storage medium encoded with a machine-readable computer program code for ascertaining status of an electric machine coupled to a polyphase bus, said storage medium including instruction for causing a controller to implement a diagnostics method comprising:

• detecting a rotational position of said electric machine with a position encoder coupled to said electric machine;
• controlling an inverter comprising a plurality of switching devices, said inverter having an input coupled to a direct current bus and an output coupled to said polyphase bus, said inverter responsive to commands from a controller coupled to said inverter and to said position encoder;
• measuring a current from said direct current bus;
• capturing a torque current;
• calculating a current error
• establishing a bound limit for said torque current;
• comparing said current error value to said bound limit;
• determining whether a fault exists by evaluating if said bound limit has been exceeded and generating a current error;
• incrementing a fault counter by a first predetermined count if said fault exists;
• decrementing said fault counter by a second predetermined count if no fault exists;
• and
• indicating a failure if said fault counter exceeds a predetermined limit.

A computer data signal embodied in a carrier wave for ascertaining status of an electric machine coupled to a polyphase bus, said data signal comprising code configured to cause a controller to implement a diagnostics method comprising:

• detecting a rotational position of said electric machine with a position encoder coupled to said electric machine;
• controlling an inverter comprising a plurality of switching devices, said inverter having an input coupled to a direct current bus and an output coupled to said polyphase bus, said inverter responsive to commands from a controller coupled to said inverter and to said position encoder;
• measuring a current from said direct current bus;
• capturing a torque current;
• calculating a current error
• establishing a bound limit for said torque current;
• comparing said current error value to said bound limit;
• determining whether a fault exists by evaluating if said bound limit has been exceeded and generating a current error;
• incrementing a fault counter by a first predetermined count if said fault exists;
• decrementing said fault counter by a second predetermined count if no fault exists;
• and
• indicating a failure if said fault counter exceeds a predetermined limit.