Low-cost power meter for the characterisation of inverter-fed electrical machines

This paper describes a versatile though low cost power meter that was specifically conceived for the characterisation of inverter-fed electrical machines. The power meter has been designed to perform a measurement of the electrical quantities associated to the first harmonics that are obtained with an uncertainty of less than 0.1%. The power meter is simple and cheap thanks to the restriction of the measurement capabilities to the first harmonics, which allows low cost converters to be used. The wattmeter employs a Digital Signal Processor to obtain a measuring rate in excess of 2 Hz; a conventional personal computer is used for the graphical interface. The power meter characterisation is obtained by means of a specially designed generator that allows distorted though known waveforms to he generated