DERIVING AN AVERAGE VALUE OF A MOTOR CURRENT DRIVE WAVEFORM

摘要

An effective use of instrumentation in a test setup where asynchronous data is neither repeatablenor consistent is problematic when testing a unit to given test specifications. This defines theelectrical current data taken of a cyclical waveform on an oscilloscope during production testingof a six-step motor drive. The test specification required that a measurement of the total average‘on’ current of the waveform be taken and compared to pass-fail criteria. To resolve this, analgorithm for determining which data points are ‘on’ current versus those ‘off’ current, andaveraging these data points to provide the ‘on’ current values was developed. The data recordedconsisted of data points taken from an oscilloscope single shot picture of the waveform,representing time-varying current output versus time. The effects of noise within theinstrumentation and timing issues added to the complexity of processing the data. The valuesobtained through this algorithm for averaging current correlated well with measurementsobtained from the UUT (Unit Under Test) telemetry and provided consistent, repeatable results.