POLYPHASE CONTROLLED RECTIFIER BRIDGE SYSTEMS AND TO ALTER NATING CURRENT GENERATOR EXCITATION ARRANGEMENTS EMPLOYING SUCH SYSTEMS

摘要

1326732 Rectifying; A.C. generators with D.C. excitation C A PARSONS & CO Ltd 4 Sept 1970 [4 Sept 1969] 43815/69 Headings H2A and H2F A poly-phase rectifying system comprises a bridge of controlled rectifiers, each branch of the bridge having at least one master controlled rectifier M1 and at least one slave controlled rectifier ST1A, a saturable core being provided for each branch having a pulse control winding 1A, a biasing winding 1B, a control winding 1C for the master rectifier M1 and a control winding 1S1 (wound in opposition) for the slave rectifier ST1A. The controlled rectifiers may be of the mercury arc type or, in a rotating-rectifier excitation system for a turbo alternator, may be thyristors or triacs and diodes. In the turboalternator described, main and control exciters are mounted on the same shaft which is provided with a flange for the mounting of the thyristors M1... M6 and ST1A.. . ST6 together with the control circuit cores. The rotor of the alternator is excited by the output of the thyristor bridge shown which rectifies the three-phase output of the main exciter rotor. The output of the rotor of the control exciter is rectified by a diode bridge D1 ... D6 and is used to provide control pulses and biasing current for the control circuit cores. At the end of each control pulse, one core becomes un-saturated so that a voltage induced in one control winding e.g. 1C, triggers one of the master thyristors M1 which then by-passes the current in winding 1C so that the resulting change of flux induces a voltage in control winding 1S1 which triggers the corresponding slave thyristor ST1A. The alternator output is retroactively controlled by varying the conduction angle of the thyristors under control of quadrature stator field windings 7, 8 in the control exciter. Short-circuit protection of the alternator output is achieved by substituting a stand-by manual control system for the automatic voltage regulator. The stationary main exciter field is supplied with D.C. from a permanent magnet generator.