Current transformer arrangement for three-wire three-phase systems to detect the actual current value for controlled DC loads powered via power converters

A current transformer arrangement for three-wire three-phase systems to detect actual current value for controlled DC loads powered via power converters having rectifiers controlled via control pulses, comprising:

• a single current transformer comprising a bushing transformer with a primary side and a secondary, said bushing transformer being on a three-phase side of the three phase system and only two phase conductor wires of the three phase conductor wires are passed through the primary side of the current transformer, in order to avoid the occurrence of a zero resultant magnetic flux the two phase conductor wires pass through the current transformer with the same current flow direction and the same number of turns per unit length but with a current amount halved in a phase conductor by a shunt;
• a correcting circuit means connected to said secondary side for halving a double measuring voltage occurring on the secondary side as a result of resultant double magnetic flux, and said correcting circuit means including means for deriving correction control pulses for switching the correcting circuit means in and out from the control pulses for the rectifiers of the power converter.

A current transformer arrangement for three-wire three-phase systems to detect actual current value for controlled DC loads powered via power converters having rectifiers controlled via control pulses, comprising:

• a single current transformer comprising a bushing transformer with a primary side and a secondary, said bushing transformer being on a three-phase side of the three phase system and only two phase conductor wires of the three phase conductor wires are passed through the primary side of the current transformer, in order to avoid the occurrence of a zero resultant magnetic flux the two phase conductor wires pass through the current transformer with the same numbers of turns per unit length but in mutually opposite current flow directions;
• a correcting circuit means connected to said secondary side for halving a double measuring voltage occurring on the secondary side as a result of resultant double magnetic flux, and said correcting circuit means including means for deriving correction control pulses for switching the correcting circuit means in and out from the control pulses for the rectifiers of the power converter.