Abstract: The invention relates to roller unit consisting of an inductively heated roller, a drive motor, an inductor and a frequency converter. According to the invention not only the converter but also the temperature regulator for the induction heater and monitoring devices for the roller, heater and/or motor are integrated into the roller unit. The power electronics and the regulator are mounted on a common cooling unit which is cooled by a coolant which at the same time also cools the motor, the bearings and the inductor.

Abstract: For monitoring the appropriate operation of a plurality of control loops having the same setpoint, the control ratio is measured at each controller, is normalized and an alarm signal is generated if said normalized control ratio exceeds a predetermined alarm band.

Abstract: For heating synthetic yarns and fibers an elongated vessel filled with saturated steam is provided through which the yarn is continuously drawn. The steam condensates on the yarn and transfers its condensation heat to the yarn. For sealing the vessel (3) at the inlet (2) and the outlet (4), several apertures (6-9, 13-16) are provided in a pair of tubes (5,12) surrounding the traveling path of the yarn (1). The space between the first aperture and the opening adjacent the steam vessel (3) is connected to a blocking liquid supply pipe (30) and the space between the last aperture (9,16) and the inlet hole (10) and the outlet hole (17), respectively, for the yarn is connected to a blocking liquid return pipe (31). The blocking liquid supply pipe is kept under a pressure which is somewhat higher than the pressure within the steam vessel (3).