Digital speed and phase control system for three-rotor type neutron choppers

Abstract

Three-rotor type neutron beam choppers have been successfully phase-controlled when driven by 400 W d.c. motors. A novel, simple and accurate method for the control of the speed and the phase difference of three motors is described. The first motor is accurately speed controlled by a digital speed controller, while the second and the third motor are pahse controlled by digital phase controllers so as to follow the first motor keeping arbitrary phase differences among them. This new chopper drive system is simpler to operate, less expensive and more accurate than the ordinary system, using synchronous motors. In this system digital techniques are adopted to the essential parts of the control system and the monitor system, so this system is especially suitable for program control and data processing by a central digital computer and high absolute accuracy and no drift are guaranteed by the digital system. All components used in this chopper controller are solid state devices and high reliability can be expected. Experimental results are as follows: speed error: 3 × 10 −3% and phase error: 0.6°.