COMPARISON OF CHARACTERISTICS OF FREQUENCY CONVERTERS IN THE SYSTEM OF AUTOMATIC CONTROL OF AN ELECTRIC DRIVE BASED ON SIEMENS S-1200

Abstract

This study provides a comprehensive experimental analysis and comparative evaluation of two widely used frequency converters — Siemens SINAMICS G120 (with PM240-2 power module) and SEW-Eurodrive Movimax MDX61B. The research is driven by the increasing industrial demand for energy efficiency and high-performance automated electric drives, which account for a significant portion of global electricity consumption. The core objective of the work is to assess energy efficiency, parameter stability, and dynamic qualities of these converters when controlling a three-phase asynchronous motor in idle (no-load) mode.The experimental setup was built around a RAVEO RT1A 562-4 induction motor controlled by a Siemens S7-1200 (CPU 1214C) programmable logic controller (PLC). Data acquisition and monitoring were facilitated through a SIMATIC KTP700 Basic PN HMI panel and integrated hardware tools within the converters, connected via a PROFINET network for synchronous data exchange. The testing methodology involved operating the motor across a wide speed range (100 to 1500 rpm) with a fixed acceleration and deceleration time of 2 seconds.The findings reveal significant differences in performance across three main operational modes:Standby Mode: The Siemens SINAMICS G120 demonstrated superior energy efficiency with a loss current of 0.0015–0.0024 A, compared to a stable 0.004 A for the SEW MDX61B. This suggests a more efficient design of power switches and driver control circuits in the Siemens model, making it preferable for systems with long idle periods.Steady-State Idle Mode: Contrary to standby results, the SEW MDX61B proved more efficient during active rotation, showing 8% to 19% lower idle currents across the entire speed range. The study attributes this to a complex adaptive flux control algorithm that optimizes energy consumption by reducing steel losses. In contrast, the SINAMICS G120 follows a classic V/f characteristic with higher, more speed-dependent currents (0.619 A to 0.548 A).Dynamic Regimes: During a 2-second ramp-up to 300 rpm, the SINAMICS G120 exhibited "tougher" dynamics with peak currents reaching 0.74 A, indicating rapid energy saturation for high-inertia mechanisms. The SEW MDX61B provided "softer" dynamics with peak currents not exceeding 0.56 A, which reduces mechanical stress on bearings and belts while preventing power grid surges.In conclusion, the research highlights that the choice of a frequency converter must align with specific technological requirements. The SINAMICS G120 is recommended for applications requiring high dynamics and having long standby intervals, whereas the SEW MDX61B is ideal for processes prioritizing steady-state energy savings and mechanical longevity. Future research will focus on performance under variable mechanical loads and harmonic analysis.