Patent ID: 9535107
Date: 2017-01-03
CPC Classifications: G01R

Claim:
1. A diagnosis apparatus for diagnosing deterioration of a DC link capacitor of an inverter having the DC link capacitor and an inverter part comprising a plurality of switching devices generating three phase AC voltages to a load connected to the diagnosis apparatus, the diagnosis apparatus comprising: a current detector configured to detect a current supplied to a motor in the inverter part; a switching mode power supplier (SMPS) configured to supply a DC voltage and to be coupled to the DC link capacitor; and a controller configured to control the DC voltage supplied from the SMPS to the motor to have a predetermined level, the controller being arranged to estimate the change of a ratio of a deteriorated capacitance to an initial capacitance of the DC link capacitor by considering power consumption of the motor, power consumption of the SMPS and a switching loss of the inverter part, wherein the estimation includes, in response to the voltage of the DC link capacitor reaching a predetermined final level: determining a first factor, k_old, based on a ratio of the power consumption of the SMPS and switching loss to power consumption of the motor using the deteriorated capacitance of the DC link capacitor, determining a second factor, k_int, based on a ratio of the power consumption of the SMPS and switching loss to power consumption of the motor using the initial capacitance of the DC capacitor, determining a first product by multiplying the first factor, k_old, with a rate of the power consumption of the motor using the deteriorated capacitance of the DC link capacitor, determining a second product by multiplying the second factor, k_int, with the rate of the power consumption of the motor using the initial capacitance of the DC link capacitor, determining a quotient of the first and second products to diagnose the DC link capacitor, and controlling the plurality of switching devices in a preset manner such that the controller detects the capacitance of the DC link capacitor.