| CPC H02P 6/21 (2016.02) | 15 Claims |
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1. A method of operating an electric motor system to provide a motor load, the electric motor system comprising:
a motor comprising:
a rotor having a magnet mounted thereto;
a motor stator that comprises one or more phases or windings for driving rotation of the rotor when the phases or windings receive an input voltage from an electrical power supply, the input voltage having a variable frequency; and
a controller that is operable to determine a back EMF induced in the motor stator;
the method comprising:
during a start-up cycle in which the input voltage frequency is progressively increased:
initially operating the motor in an open loop mode in which an open loop rotor angle is estimated based on the input voltage frequency;
operating the motor during a transition period where the rotor angle is determined based on both the open loop rotor angle of the open loop mode and a closed loop rotor angle of a closed loop mode, wherein the transition period is defined between a first input voltage frequency threshold and a second input voltage frequency threshold; and
after the input voltage frequency reaches the second input voltage frequency threshold, operating in the closed loop mode,
wherein the closed loop rotor angle is determined based on the back EMF determined by the controller.
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