Toshiaki Kurosawa

A New Speed Control System for DC Motors Using GTO Converter and its Application to Elevators

A dc motor control system using a new GTO converter, is developed for an intermediate-speed elevator (2.5-m/s rated speed and 1000-kg load). Its features include 1) a main circuit control system composed of pulsewidth and phase controls, 2) a circuit to suppress the overvoltage which occurs when the GTO is turned off, 3) direct digital control which is composed of an acceleration control to compensate for lag time in the field current response and a self-correcting function to compensate for landing error. Application of the control system provided a higher power factor and smaller power consumption than a conventional control system.

A New Speed-Control System for DC Motors and its Application to Elevators

A circuit with a unidirectional armature current and bidirectional field current was used in order to realize a high-reliability speed-control system for dc motors by simplifying the armature circuit construction in comparison with conventional Thyristor-Leonard speed-control systems. In making the new circuit feasible, we developed a system in which either armature current or field current is fixed and the other varies depending on the magnitude of the torque command; a high-reliability magnetically controlled three-phase thyristor amplifier; and minor feedback loops provided with a field current control circuit and armature current control circuit. By using these techniques, we developed a dc motor control system that features higher reliability and smaller power consumption than conventional control systems. The new system was applied to elevator control with good results.

Horizontal vibration suppression method suitable for super-high-speed elevators

Horizontal vibrations of elevator cars mainly occur because a car swings as roller guides installed at corners of a car frame move on a winding guide rail at high speeds. Rider comfort in high-speed elevators is worsened by these vibrations. Conventional active dampers suppressing horizontal vibrations using ac servomotors make cars heavier so driving power becomes larger, and they are not easily applied to existing elevators. An active damping control method suited to super-high-speed elevators is described which can solve these problems. The method suppresses vibrations by generating only enough magnetic force needed to suppress them only when vibrations of the car frame are produced. The vibrations are detected using acceleration detectors and magnets installed on the left and right sides of the car frame. A computer simulator was made to analyze phenomena of car vibrations and to verify effects of the proposed magnetic damping controller. It was found that the vibrations generated on the cabin floor were remarkably large when the left and right sides at the upper and lower parts of the car frame were swung by sine waves with the same phase. The vibrations had two resonant modes. Results obtained with the computer simulator and a full-scale running simulator showed that the acceleration on the cabin floor, even at the resonant frequencies, could be reduced by the magnetic damping control to around 0.1 m/s2 which would provide a comfortable ride.