Method and apparatus for controlling three-phase electric motor
A three-phase motor and phase current technology, applied in the starter of a single multi-phase induction motor, the deceleration device of an AC motor, motor control, etc., to achieve the effect of improving reliability and efficiency
Inactive Publication Date: 2019-02-05
POWER DRIVE EFFICIENCY LTD
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Problems solved by technology
[0022] The present invention solves problems particularly in situations where precise speed control is not required but in different Technical Problems in Reducing Energy Consumption in Three-Phase Motor Drives Operating Under Load
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[0048] Referring now to the accompanying drawings, figure 1 A three-phase motor 1 powered by a three-phase mains supply 2 and mechanically connected to a load 3 is shown schematically. The rotor of the electric machine 1 is connected to a mechanical load 3 via a transmitter 4 .
[0049] In the case of a rotating load, the inertia of the load 3 may require high torque from the motor 1 during the acceleration phase, but once the load reaches its rotational speed, the motor's torque requirement may decrease. As the load decelerates, the inertia of the load will continue to "drive" the motor during this deceleration phase.
[0050] A three-phase motor 1 has three stator windings and six terminals 5 on the motor body, each terminal being connected to a respective end of one of the stator windings. In the embodiment shown, three of the terminals 5 are connected to respective phases of the three-phase mains supply, and all terminals 5 are connected to the control unit 6 . Within t...
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Methods and control apparatus for operating a three-phase electric motor are described, in which the motor windings are switched between Star and Delta connections depending on torque requirements, and in which the motor windings are switched to a braking mode when braking torque is required. The electromagnetic torque of the motor is monitored, and a command to switch from Star to Delta is givenwhen the electromagnetic torque rises to reach or exceed a threshold. A command to switch from Delta to Star is given when the electromagnetic torque falls to reach a second threshold. The invention discloses a method of determining instantaneous values for the electromagnetic torque of the motor based on measurements of phase current and phase voltage at particular instants in the voltage cycle.The application further discloses a method of timing the switching operation between Star and Delta configurations, or switching from Star or Delta configuration to a dynamic braking mode, to minimiseinrush currents by monitoring the vector relationship between the EMF and the supply voltage and performing switching operations in each motor phase when EMF vector is aligned with the supply voltagevector. The application further discloses switching from Star to Delta or Delta to Star when the torque produced by the motor is substantially equal to the torque requirement of the load to maximiseefficiency.
Description
technical field [0001] The invention relates to the control of three-phase AC motors. In particular, the invention relates to apparatus and methods for controlling three-phase AC motors, especially asynchronous motors, to drive mechanical devices or mechanisms that do not require precise speed control. The invention is of particular utility in the field of motor drives with frequent starting and braking cycles and with variable loads. Examples of such machines are mixers, cranes, elevators, centrifugal casting machines and metal fabrication machines. The invention is also of utility in the field of continuously operating mechanisms that do not require precise speed control, examples being pumps, fans, compressors, conveyors, escalators, and ventilators. Background technique [0002] Three-phase alternating current (AC) motors used to drive industrial machines or facilities typically have three motor windings in the stator and operate on a three-phase electrical power suppl...
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IPC IPC(8): H02P1/32H02P25/18H02P3/24G01R21/06G01R31/34
CPCH02P25/184H02P1/32H02P2207/01G01R21/06G01R31/34H02P3/18H02P2205/05H02P3/24H02P25/18H02P29/40
Inventor 伊戈尔·亚历山大·图雷夫斯基摩西·海姆·奈曼阿蒂尔·奈曼
Owner POWER DRIVE EFFICIENCY LTD