Gate-Turn-Off thyristor commutation of DC machines : The development of a rotating DC machine with static commutation of armature coil current using Gate-Turn-Off thyristor devices.

摘要

The thesis Is concerned with the development of a separatelyudexcited DC machine In which gate turn-off thyristor devices withudtheir associated firing and protective circuits are used to provideudthe static commutation of armature coil current. The developedudmachine has Its armature winding with 24 tapping points located onudthe stator and Interconnected In "Lop" configuration. TheudInitiation of the conduction periods of armature switching devicesudIs defined by a digital control logic circuit. In conjunction withudan Incremental rotary encoder which provides the necessary feedbackudInformation relating to shaft speed and shaft angular position.udThis Is arranged such that, under normal running conditions of theudmachine, the axis of the radial field of the armature windingudmaintains the normal space-quadrature relationship with that of theudmain field winding, giving the optimal torque angle of 000.udProvision Is made, however, within the digital control circuit forudcontrolled departure of the armature switch tapping points from theudquadrature axis positions, and the effect of this, In Improvingudcommutation Is Investigated. The effect of Interpoles Is alsoudexplored. On the basis of the analysis carried out, a proposal Isudmade for the future development of the machine employing a reducedudnumber of armature switching devices without the need for Interpoleudwindings.