A study on electrical performance of modern VVVF drives for HVAC applications

As the “energy conservation” concept has been widely accepted by most engineers and building professionals, the power electronics variable speed drives have been very popular in the building industry, in particular, in the area of heating, ventilation and air-conditioning (HVAC) applications because this is the area where a substantial energy consumption exists in a modern commercial building. This paper first of all highlights the operating principle of the modern variable voltage variable frequency (VVVF) drives and discusses its impact on the electrical power distribution system in the buildings. A typical off-the-shelf VVVF drive for HVAC application was examined by a comprehensive testing arrangement in the “Electric Drive Laboratory” inside the Department of Building and Construction of City University of Hong Kong. The methods of assessment have been included in this paper together with the technical results. Furthermore, the records of a comprehensive site measurement of the drive are summarised in this paper as well to give the readers a clearer understanding of the real application. The argument of using “fundamental power factor” or “total power factor” to describe the power factor of a VVVF drive has also been highlighted in this paper as a means to raise discussion between various parties concerned