A chiller assembly, comprising: - a compressor, a condenser, an expansion device, and an evaporator connected in a closed refrigerant circuit; - a motor (104, 328) connected to the compressor to power the compressor; - a variable speed drive (110, 302) operable to provide a variable voltage to the motor (104, 328) and a variable frequency to power the motor (104, 328), the variable speed drive (110, 302) comprising: - a plurality of sensors; and - an input current estimator operable to determine an estimated RMS input current based at least in part on sensor data received from the plurality of sensors, wherein the sensor data comprises a DC link voltage value and a DC link current value, and wherein the input current estimator is operable to determine: - a DC link power value based at least in part on the DC link voltage value and the DC link current value; - a line-to-line input voltage value based at least in part on the DC link voltage value, an input line frequency value, a line inductance value, and the DC link current value; - an input current value based at least in part on the DC link power value and the line-to-line input voltage value; - an input current with distortion value based at least in part on the input current value and a determination of whether an active harmonic filter is operable; - a transformer current value based at least in part on the line-to-line input voltage value; and - a total input RMS current value based at least in part on the input current with distortion value and the transformer current value; and - a control panel to control operation of the variable speed drive (110, 302) and one or more components of the chiller assembly. - a compressor, a condenser, an expansion device, and an evaporator connected in a closed refrigerant circuit; - a motor (104, 328) connected to the compressor to power the compressor; - a variable speed drive (110, 302) operable to provide a variable voltage to the motor (104, 328) and a variable frequency to power the motor (104, 328), the variable speed drive (110, 302) comprising: - a plurality of sensors; and - an input current estimator operable to determine an estimated RMS input current based at least in part on sensor data received from the plurality of sensors, wherein the sensor data comprises a DC link voltage value and a DC link current value, and wherein the input current estimator is operable to determine: - a DC link power value based at least in part on the DC link voltage value and the DC link current value; - a line-to-line input voltage value based at least in part on the DC link voltage value, an input line frequency value, a line inductance value, and the DC link current value; - an input current value based at least in part on the DC link power value and the line-to-line input voltage value; - an input current with distortion value based at least in part on the input current value and a determination of whether an active harmonic filter is operable; - a transformer current value based at least in part on the line-to-line input voltage value; and - a total input RMS current value based at least in part on the input current with distortion value and the transformer current value; and - a plurality of sensors; and - an input current estimator operable to determine an estimated RMS input current based at least in part on sensor data received from the plurality of sensors, wherein the sensor data comprises a DC link voltage value and a DC link current value, and wherein the input current estimator is operable to determine: - a DC link power value based at least in part on the DC link voltage value and the DC link current value; - a line-to-line input voltage value based at least in part on the DC link voltage value, an input line frequency value, a line inductance value, and the DC link current value; - an input current value based at least in part on the DC link power value and the line-to-line input voltage value; - an input current with distortion value based at least in part on the input current value and a determination of whether an active harmonic filter is operable; - a transformer current value based at least in part on the line-to-line input voltage value; and - a total input RMS current value based at least in part on the input current with distortion value and the transformer current value; and - a DC link power value based at least in part on the DC link voltage value and the DC link current value; - a line-to-line input voltage value based at least in part on the DC link voltage value, an input line frequency value, a line inductance value, and the DC link current value; - an input current value based at least in part on the DC link power value and the line-to-line input voltage value; - an input current with distortion value based at least in part on the input current value and a determination of whether an active harmonic filter is operable; - a transformer current value based at least in part on the line-to-line input voltage value; and - a total input RMS current value based at least in part on the input current with distortion value and the transformer current value; and - a control panel to control operation of the variable speed drive (110, 302) and one or more components of the chiller assembly.