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.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:452669 |
| Date | January 1977 |
| Creators | Crowder, Richard Michael |
| Publisher | University of Leicester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/2381/34755 |
Page generated in 0.0019 seconds