ON MINIMAL INDUCTION OF THYRISTOR DRIVE SMOOTHING THROTTLE UNDER CONVERTER EDGE OPERATING CONDITIONS

Abstract

The smoothing throttle operations in the DC-motor circuit of a thyristor drive are studied. The main mathematical and graphic dependences of the smoothing throttle Lс inductance modification on the control angle, and on the number of the thyristor converter (TC) phases are given. The situation of the technological machine (TM) executing mechanism (EM) low conveying speed and of the armature pulsating current zone (PCZ) reduction is considered. In this case, it is reasonable to determine the minimal induction value of the smoothing throttle (Lс) at the boundary control angle αboun equal to 50—60 electric degrees for the increase in the mechanical characteristic rigidity of the DC motor. Then, the throttle magnetic conductor condition is defined by the branches of the specific limit asymmetric hysteresis cycle characterizing the electromagnetic processes in the magnetic conductor under the influence of the unipolar current pulses. Thus, the efficiency of the throttle core usage is defined through the incremental induction, i.e. through the difference in the residual induction B(0) levels, and the magnetic conductor material saturation induction. The airgap injection (δ) stabilizes the core equivalent magnetic capacity which can be broken by heating the throttle magnetic conductor with the armature current, by the environmental temperature fluctuations, and by the operation conditions of the thyristor drive. At the minimum inductance Lc of a smoothing throttle (for a boundary angle αboun), effects of the stabilizing factors of the core equivalent magnetic capacity (with airgap δ) decrease, PCZ is excluded. This permits to reduce electric losses in the power contour of the TC — DC-motor system, and also to form the required rigidity of the DC-motor mechanical characteristics, and the TM EM movement steadiness in the anchor low rotation frequency zones.