Circuit arrangement for feeding a measurement variable transformer

摘要

For the DC isolation of analogue direct-current signals, it is known to use an isolating transformer into the secondary winding of which an auxiliary direct voltage is fed via a chopper circuit. The secondary feed circuit is connected in series with the output circuit so that there is no DC isolation between the auxiliary power circuit and the output circuit. A feed circuit for a measurement transformer is provided which manages with one isolating transformer and ensures DC isolation between auxiliary power, input and output circuit. The transformer exhibits a primary winding for the feed circuit, a first secondary winding for the input circuit and a second secondary winding for the output circuit. The feed current is a constant current.