Analyzing the active power of variable frequency drives in manufacturing plants

In multi-axis machining centers the individual operating loads of axis and spindle drives are often unknown. Especially in serial production, drive systems are oversized including electric motors, frequency inverters and shaft drives. But also in special plant engineering, where multiple drive systems are connected to one intermediate circuit, the individual operating loads cannot be assessed. Subsequently, performance, operating points and energy efficiency are suboptimal. Economic disadvantages, such as the necessity of higher investments and increased operational costs, are associated. Therefore an approach to active power measurement behind the frequency inverter to separate the power consumption profiles of spindle and axis drives is necessary. In this paper two systems for an active power measurement for variable frequency drives are discussed. One of them has been developed by the authors themselves with the advantage of lower cost compared to commercially available systems. The systems were analyzed for performance, accuracy, installation effort and costs. The investigated active power measurement systems provide basic data for an optimal dimensioning of drive systems for industrial equipment manufacturers.