Further Study on Total Power Factor of a Lift System

摘要

The electrical parameter "Total Power Factor" (TPF in short) is extremely important in checking how good a power supply is supplying its load. This term has been used for more than a century with some changes in the method of evaluation in the sixties when power electronic drives started to become popular. For a standard single phase or 3-phase 4-wire (3P4W) or 3-phase balanced system, the existing definition of TPF is perfect. However, most lift systems are operating on a 3-phase 3-wire (3P3W) power supply while the 3-phase voltages and currents are not 100% balanced based on our site measuring experience. In other words, the existing definition of TPF does not normally apply to any lift system, and meters available in the market also cannot give a correct TPF for lift systems. A new definition of TPF mainly for lift systems was proposed and further study on this definition was recently carried out. A new method to convert the measurable three line voltages into non-measurable three phase voltages of a 3P3W system was suggested. An APP was developed for on-site engineers to easily get the correct value of TPF based on simple and easy measurements. This article serves to provide a summary on works done by us on this issue, hoping that the problem has ultimately been solved, and codes are round the world could properly adopt this new method.