# Rieter

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Modern high-performance ring spinning machines need very good speed control, i.e. the speed must be independent of variations in load and mains voltage. Absolute observance of the speed ramps is a precondition for good running behavior, mainly during the dynamic start and stop operations. This requirement can be fulfilled easily and at low cost by using a normal asynchronous motor connected to a current-controlled frequency inverter. The additional advantages of this drive system are good overall efficiency, a wide range of motor speeds (0 - 6 000 rpm), simple change of direction of rotation, absence of demand for reactive volt-amperes from the mains supply $(cos\ \phi\cong 1.0)$ and only a small, i.e. normal load on the power supply system during machine start-up. However, the system needs a sophisticated electronic control system.