Method for sensorless operation of an ECM, and motor for carrying out
Assigneeebm-papst St. Georgen GmbH & Co. KG
InventorKonstantin Dornhof
Life of this patent
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Abstract
An electronically commutated motor (ECM) often employs a Hall sensor for reliable operation. Even when a Hall sensor is omitted from a motor having a plurality of stator winding phases (24, 26) and a permanent-magnet rotor (22), one can reliably detect direction of rotation of the rotor by the steps of: (a) differentiating a voltage profile obtained by sampling either (1) induced voltage in a presently currentless phase winding or (2) voltage drop at a transistor, through which current is flowing to a presently energized phase winding, and (b) using such a differentiated signal (du—24″/dt, du—26″/dt) to control current flow in an associated phase winding. In this manner, one obtains reliable commutation, even if the motor is spatially separated from its commutation electronics.
Claims7
A method of sensing the direction of rotation in an electronically commutated motor (ECM) having a stator with a plurality of phases (24, 26) and a permanent-magnet rotor (22), which rotor (22), during its rotation, induces voltages in the motor winding phases (24, 26) of the stator,
- comprising the steps of:
- a) commutating the motor at a first time point, and at a second time point subsequent to said first time point, a time interval between said first and second time points defining a commutation period;
- b) sampling, at a plurality of characteristic points during said commutation period, either the profile of induced voltage in a presently currentless motor winding phase or the profile of a voltage drop at a transistor through which current is flowing to a presently energized motor winding phase, and storing measured values thereof;
- and
- c) deriving, from the measured values, rotor rotation direction;
- wherein there exists a predetermined time span (Tp) between two zero transitions of the induced voltage occurring in a currentless phase, or between two zero transitions of the voltage drop at the transistor through which current is flowing to the presently energized phase;
- and
- sampling is performed, to store a first measured value, at a time interval after a zero transition that is equal to approximately 20 to 30% of that predetermined time span (Tp).
A method of sensing the direction of rotation in an electronically commutated motor (ECM) having a stator with a plurality of phases (24, 26) and a permanent-magnet rotor (22), which rotor (22), during its rotation, induces voltages in the motor winding phases (24, 26) of the stator,
- comprising the steps of:
- commutating the motor at a first time point, and at a second time point subsequent to said first time point, a time interval between said first and second time points defining a commutation period;
- sampling, at a plurality of characteristic points during said commutation period, either the profile of induced voltage in a presently currentless motor winding phase or the profile of a voltage drop at a transistor through which current is flowing to a presently energized motor winding phase, and storing measured values thereof;
- shortly before and shortly after the sensing of a measured value (SM1;
- SM2), sensing at least one respective value (NM1, NM2) characterizing the operating voltage (UB);
- from those sensed values, deriving a value which characterizes the noise voltages that are superimposed on the operating voltage, and
- using said derived value to correct a temporally adjacent measured value;
- and
- deriving, from the measured values, rotor rotation direction.
A method of sensorless control of commutation in an electronically commutated motor, which motor comprises a stator having at least two phases (24, 26, 28) and a permanent-magnet rotor (22), said rotor inducing, during its rotation, a voltage in said at least two phases, each phase having, associated with it, a respective transistor (40, 42, 43) to control current in the phase, and each phase having, associated with it, a respective terminal (24″, 26″, 28″), each terminal being connected to the phase and to the transistor,
- comprising the steps of:
- a) differentiating over time, for a plurality of phases (24, 26, 28), respective voltage signals tapped at said respective terminals to produce derivatives over time;
- and
- b) comparing said derivatives over time with one another to control current flow in an associated phase (24, 26, 28) of the stator.
A method of sensorless control of commutation in an electronically commutated motor, which motor comprises a stator having at least one winding phase (24, 26) and a permanent-magnet rotor (22), said rotor inducing, during its rotation, a voltage in said at least one winding phase (24, 26),
- comprising the steps of:
- a) differentiating the induced voltage in the at least one phase, or the voltage drop at a transistor through which current is flowing to the presently energized phase, to produce a differentiated signal;
- b) using that differentiated signal to control current flow in an associated winding phase (24, 26) of the stator;
- c) calculating a derivative over time for the at least one phase, and during a first portion of the rotation of the rotor (22), measuring a time interval (Tk′) from a first zero transition (180) of that derivative to a second zero transition (176) thereof;
- and
- d) using that measured time interval (Tk′) to control commutation during a subsequent second portion of the rotation of the rotor (22).
Dependencies are inferred from the claim text.