Control of motor soft starter using power electronic switching devices
AssigneeEaton Intelligent Power Limited
InventorsJin Li, Xin Zhou, Steven A. Dimino, Kaijam Maurice Woodley
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Abstract
Systems and methods for soft starting a motor (40) using solid-state switching devices are disclosed. The system (10) includes a soft starting switch (53) that is made of a plurality of solid-state switches (62, 63). The system (10) also includes a controller (86) that is programmed to regulate currents and voltages delivered to the motor (40) during a start-up operation of the motor by cycling the solid-state switches (62, 63) ON and OFF during the start-up operation.
Claims11
A method of soft starting a motor, the method comprising:
- providing a soft starting switch that is electrically connected between a power source and an alternating current (AC) motor, wherein:
- the soft starting switch comprises one or more phases, each of which comprises:
- a power electronic switching device that comprises a plurality of solid-state switches electrically connected in series or in parallel with each other;
- and
- by a controller, cycling the solid-state switches ON and OFF during a start-up operation to regulate currents and voltages delivered to the AC motor during the start-up operation,
- wherein cycling the solid-state switches ON and OFF during the start-up operation comprises, by the controller:
- receiving current data from one or more current sensors, and detecting a plurality of Current zero crossings in the current data over a plurality of current cycles;
- receiving voltage data from one or more sensors, and detecting a plurality of current zero crossings in the voltage data over a plurality of voltage cycles;
- and
- for each phase:
- determining a firing angle for a present voltage cycle,
- using the detected voltage zero-crossings and the firing angle for the present voltage cycle to determine a time to command that phase's solid-state switches to gate ON, and
- using the detected current zero-crossings info and a current zero-crossing detection tolerance threshold to determine a time to command that phase's solid-state switches to gate OFF.
A system for soft starting a motor, the system comprising:
- a soft starting switch comprising:
- a line side for connecting to a power source and a load side for connecting to a motor, and
- a power electronic switching device that is positioned between the line side and the load side, and that comprises a plurality of solid-state switches electrically connected in series or in parallel with each other;
- a controller configured to regulate currents and voltages delivered to the motor during a start-up operation of the motor by cycling the solid-state switches ON and OFF during the start-up operation;
- one or more current sensors;
- one or more voltage sensors;
- and
- programming instructions that are configured to cause the controller to:
- receive current data from the one or more current sensors,
- detect a plurality of current zero crossings in the current data over a plurality of current cycles,
- receive voltage data from the one or more voltage sensors,
- defect a plurality of voltage zero crossings in the voltage data over a plurality of voltage cycles, and
- for each phase:
- determine a firing angle for a present voltage cycle;
- use the detected voltage zero-crossings and the firing angle for the present voltage cycle to determine a time to command that phase's solid-state switches to gate ON;
- and
- use the detected current zero-crossings information and a current zero-crossing detection tolerance threshold to determine times to command that phase's solid-state switches to gate OFF.
Dependencies are inferred from the claim text.