Abstract:
A motor control system for a hoist drive having an electric motor (2) operationally connected to a hoisting member (4) for hoisting a load (6), the motor control system being adapted to generate a final angular frequency reference (ω*s) for control of the electric motor (2), the motor control system comprising a power limiter means (8) adapted to generate a correction term (ωs,COr) for angular frequency reference. The power limiter means (8) comprises an integrating controller means (10), the power limiter means (8) being adapted to generate the correction term (ωs,COr) for angular frequency reference using output signal Ip of the integrating controller means (10), initial data of the integrating controller means (10) including information relating to actual value of the power of the electric motor (2) and a power related limit value of the electric motor (2).
Abstract:
A system and method are disclosed for turning off the voltage to a pump jack electric motor during predetermined periods of time to save energy. In the method, the motor's response to closed-loop control may be evaluated over several pump strokes. The periods of the pump stroke when it is feasible to turn off the motor may be identified. The consistency of the measurements over several strokes may be evaluated. The motor may be turned off during predetermined periods on subsequent pump strokes when each pump stroke shows sufficiently similar behavior to that predicted during the closed-loop control process. The system may return to the closed-loop control process after a predetermined period of time to adjust to any changes in the system.