In the Master thesis a method for determining the efficiency of an electric drive system (EDS) operating with variable speed is presented. The method is based on data of operating points measured on existing EDS, which needs modernization due to low efficiency.
EDS, which provides cooling water in an industrial process, was analysed. EDS consists of an electric motor, a centrifugal pump, and a frequency converter. An analysis of the system is given, where the existing components of EDS will be replaced with new and optimally dimensioned ones.
At the EDS input, electrical parameters (frequency, voltage, current, power) were measured with a power analyser, and at the EDS output, hydraulic parameters (pressure, flow) were measured with a differential pressure gauge and an ultrasonic flow meter. With gathered measurements, the efficiency of EDS and the amount of consumed electricity were calculated through the ratio of hydraulic and electrical power.
The process of modelling the efficiency characteristics for EDS components is presented. Several different combinations of EDS components are studied and analysed. We compared the efficiency of electric motors of various power and efficiency classes controlled by a frequency converter and loaded with centrifugal pumps of different diameters. A comparison of the efficiency of the new EDS combinations is given, as well as the financial savings compared to the old, existing system.
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