Variable frequency drives (VFD) are a type of power controller that will normally use pulse width modulation technology to drive an electric motor at frequencies of choice.
While this technology brings the advantage of versatile motor speed control without the need for mechanical gearing of conventional motor systems plus the additional benefits of higher efficiency, lower weight and size, the signals involved are highly distorted.
Since useful mechanical energy produced by a motor is primarily derived only from the fundamental frequency of a modulated supply voltage, frequency components of a distorted drive waveform are a significant source of motor losses. It follows that meaningful power efficiency measurement requires a much wider frequency range than has conventionally been used in motor testing.
Additionally, these applications usually involve asynchronous frequency stages, where conventional digital sampling is not ideal. Using windowing techniques that are initially counterintuitive, PPA series analyzers achieve superior measurement stability and efficiency accuracy than can be achieved with conventional digital sampling methods.
A meaningful understanding of power conversion efficiency within an electric vehicle is more complex than generally recognised, because it involves multiple power stages of very different nature.
From DC power that will often include a ripple voltage induced by variable speed drives, then the inverter losses associated with switching and distortion of the drive output and finally conversion to mechanical power, all present measurement challenges that most power measurement systems will not easily handle optimally.
Industrial Machines, pumps, and fans
The ongoing change from fixed speed motors and gearing to variable speed drives brings an associated need for wideband power analysis that is correctly synchronised with the drive speed. This becomes particularly important as motor users experience very different motor performance and efficiency, depending upon which specific drive design they use. The complex nature of losses in a VFD to motor combination requires more complex analysis of losses, so that the most effective combination of drive design for any motor type can be established.
White Goods and power tools
Compact variable speed drives allow white goods and power tools much greater flexibility of motor speed control and associated efficiency.
These benefits come however with an added challenge of stricter conducted and radiated emissions standards than are required for commercial and industrial applications.
N4L power analyzers provide the functionality and accuracy required both for precision power measurement and compliant testing to Harmonic and Flicker standards.