US Patent 7492119 Circuit arrangement for generating motor characteristic curves

A circuit arrangement (1) for generating motor characteristic curves, in particular for stabilizing the pull-out torque of a two-phase synchronous motor (2) by using a series-connected element (14). The series-connected element (14) is connected between a first line conductor (12.1) formed as a neutral conductor and the common phase (11) of the synchronous motor (2), and a second line conductor (12.2) implemented as a conductor is connected with a phase of the synchronous motor (2). A transistor-diode combination (3) is employed as a voltage-controllable series-connected element (14), whereby for obtaining an approximately constant sinusoidal AC voltage amplitude and/or AC current amplitude through the synchronous motor (2), the transistor (4) designed for the maximum peak voltage of the oscillating line voltage and having an operating point controllable by an analog control signal is a non-switched bipolar transistor or field effect transistor (FET), and the diodes (6) are implemented as a rectifier bridge (5).