System and method for detecting phase loss and diagnosing DC link capacitor health in an adjustable speed drive

A method for detecting a phase loss in an adjustable speed AC drive comprising:

• identifying a DC link current of the adjustable speed AC drive;
• providing a state observer having a state space model representation of the adjustable speed AC drive;
• inputting the identified DC link current into the state observer;
• extracting a DC link capacitor current of the adjustable speed AC drive using the state observer;
• comparing at least one component of the DC link capacitor current to a predefined fault range;
• and
• outputting a phase loss indicator if the at least one component of the DC link capacitor current is within the predefined fault range.

A non-transitory computer readable storage medium having stored thereon a computer program comprising instructions which, when executed by at least one processor, cause the at least one processor to:

• acquire a DC link current of an adjustable speed drive (ASD);
• transmit the DC link current to a state observer formulated to represent the ASD;
• extract at least one component of a DC link capacitor current of the ASD from the state observer using the DC link current, wherein extracting the at least one component comprises extracting at least one of a second harmonic component of the DC link capacitor current and a sixth harmonic component of the DC link capacitor current;
• compare the amplitude of the at least one extracted component of the DC link capacitor current to a fault range;
• and
• if the amplitude of the at least one extracted component of the DC link capacitor current is within the fault range, generate an indication of a phase loss.