U433577.pdf (107.26 MB)
Static four-quadrant control of induction motors.
thesisposted on 2015-11-19, 08:58 authored by Richard Michael. Crowder
This work describes a method of controlling a slip-ring induction motor so as to provide characteristics suitable for hoist drive applications. The primary of the machine was supplied from a three-phase voltage regulator which in addition to producing a motoring torque can also provide plug braking by phase reversal and dynamic braking by d.c. injection. The hoist drive characteristics are of a constant torque nature and these were obtained by the control of a variable duty cycle forced commutated thyristor chopper in the secondary circuit of the motor. The operation of the voltage regulator has been examined for a load consisting of a delta wound induction motor. A simple model of the regulator has been developed from which speed-torque characteristics have been determined. Analysis of the operation of the motor and thyristor chopper was used to determine the appropriate relationship between duty cycle and speed necessary to produce a constant torque characteristic. This relationship was realized by a function generator which was used to control the thyristor chopper. Closed loop control of motor speed by the voltage regulator combined with open loop operation of the thyristor chopper as a function of speed gave the required constant torque characteristic. Logic circuits were incorporated in the design to allow automatic selection of the motoring and braking modes. The four-quadrant controller has been designed and successfully operated throughout the required speed range. The operation of the controller has been considered from both steady state and dynamic aspects.
Date of award1977-01-01
Awarding institutionUniversity of Leicester