Abstract: An inverter arrangement for generating a three-phase AC output voltage is provided with three pulse-controlled, free-running single-phase inverters. The inverters are connected at their inputs to a DC voltage source, and at their outputs to respective low-pass filters. The low-pass filters are connected to corresponding single-phase transformers, each having an output winding. The output windings of the single-phase transformers are connected to one another in a Y-circuit configuration to produce the output AC voltages, having a grounded neutral terminal. Each of the single-phase inverters is controlled by an associated pulse control device which contains a vector-oriented control device and a control unit. A vector oscillator generates signals corresponding to a symmetrical three-phase system of reference vectors for the vector-oriented control devices.

Abstract: The measured rolling rate of a ship and a measured liquid level difference in a liquid contained in a stabilizing tank are supplied to frequency dependent members having identical frequency response to obtain a derived roll angle and derived level difference after which a circuit is provided to measure the phase difference between the quantities developed and to develop an output analog voltage representing the difference between a desired relationship between the phases of the two and the actual phase relationship.