Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
2002-09-19
2004-05-25
Masih, Karen (Department: 2837)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S434000, C318S132000
Reexamination Certificate
active
06741046
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of starting a sensorless and brushless direct current motor, in which the stator windings are supplied with power from a multiphase converter circuit.
BACKGROUND INFORMATION
German Published Patent Application No. 39 40 568.9 describes a circuit configuration for operating a multiphase synchronous motor on a direct current system. The phases are connected successively to the direct current voltage, and commutation switches are controlled according to the rotor position so that they overlap in time for commutation of successive phases, and at least one of the commutation switches is cycled in the commutation range so that the average current in the phase commuted up increases and the average current in the phase commuting down decreases. A lower switching power loss and noise reduction are achieved due to this overlapping and cycling of the switching signals in the commutation signal edges.
The position of the rotor in a sensorless and brushless direct current motor is purely coincidental at standstill and may not be determined. One possibility of starting up such a sensorless and brushless motor is to impose a stator rotational field via a starting oscillator. The frequency of the stator rotational field is adjusted so that the rotor is allowed to rotate with its inertia in a defined interval of time in synchronization with the imposed stator rotational field. This requires a complicated adjustment, e.g., when the mass inertia connected to the motor changes.
It is an object of the present invention to provide a reliable starting performance in the case of a multiphase sensorless and brushless direct current motor in a predetermined direction of rotation and within an overall predetermined allowed range of the direct current voltage feed applied at the converter circuit.
SUMMARY
The method according to the present invention for starting a sensorless and brushless direct current motor may provide the advantage that the rotor is pulled into a defined starting position within the shortest possible amount of time without any interfering vibration, and from this starting position it may be started quickly and reliably in the desired direction of rotation. The method according to the present invention is to a large extent insensitive to changes in the moment of inertia of the rotor, This may have the additional advantage that when used in fan applications, for example, the same direct current motor may be equipped with different fans without having to alter the control of the direct current motor.
In the method according to the present invention, the rotor is in principle first rotated into a defined starting position for startup in an alignment operation by simultaneously feeding power to at least two phases of the stator winding and then initiating an energization state of the stator windings which applies a sufficient torque in the desired direction of rotation, whereupon then the additional energization states of the corresponding phases follow in a cyclic pattern and the rotor is made to rotate in synchronization with the applied stator rotational field.
According to an example embodiment of the method according to the present invention, the second energization state of the stator windings is initiated as an energization state which applies a sufficient torque.
In an example embodiment of the method according to the present invention, the current and pulse width in pulse-width modulation of the current, which is supplied to the phases in energization of the two phases in the orientation operation are increased according to a certain curve.
According to another example embodiment, the curve with which the current and pulse width are increased is in the form of a ramp or a parabola. It is possible with this configuration of the alignment operation and the respective current, as provided for in another example embodiment, for the current and pulse width in pulse width modulation of the current to be varied according to the input direct current voltage applied at the converter circuit; e.g., in the case of a low direct current voltage, the current and pulse width are increased, and in the, case of a high direct current voltage, the current and pulse width are reduced. This may allow for adaptation to the strong fluctuations in battery voltage, which occur very often especially in a motor vehicle, and nevertheless permits reliable alignment and starting of the direct current motor.
This also may provide the advantage that the area of applications for such a motor is very broad because it has practically no sensitivity to changes in the mass inertia of the rotor. It may be possible for different loads to be attached to the motor.
In another example embodiment of the method according to the present invention, a suitable phase is analyzed, e.g., by detecting whether it has dropped below a commutation threshold, for commutation detection, e.g., by a zero crossing of the induced voltage of the non-energized phase.
In another example embodiment of the method according to the present invention, a microcontroller is provided for controlling and implementing the method, and a commutation interrupt is triggered when commutation is detected. Due to the interrupt routine thus called up, energization of the stator windings is switched to the next energization state.
In another example embodiment, the increase in the waveform of the current and pulse width and/or its dependence on the input direct current voltage of the converter circuit is stored in a read memory of the microcontroller. Therefore, once the waveform has been determined, it is available with each startup according to the input direct current voltage just applied in a suitably adapted form.
In another example embodiment of the method according to the present invention, this is applied to an external rotor motor, and permanent magnets are provided with alternating north and south poles on the internal perimeter in the bell of the external rotor motor. The method according to the present invention may of course also be used for internal rotor motors.
In another application of the method according to the present invention, it is used in a motor which is supplied with direct current power from a battery or the on-board electric system of a motor vehicle.
The method according to the present invention is explained in greater detail in the following description on the basis of an example embodiment of a sensorless and brushless direct current motor which is illustrated in the drawings.
REFERENCES:
patent: 4047084 (1977-09-01), Ban
patent: 5198733 (1993-03-01), Wright
patent: 5350984 (1994-09-01), Carobolante et al.
patent: 5466999 (1995-11-01), Hutsell
patent: 5489831 (1996-02-01), Harris
patent: 39 40 568 (1991-04-01), None
patent: 2 590 423 (1987-05-01), None
patent: 1-308192 (1989-12-01), None
patent: 11-243698 (1999-09-01), None
patent: 2000-104981 (2000-04-01), None
Patent Abstracts of Japan, vol. 14, No. 108 (E-896), Feb. 27, 1990.
Patent Abstracts of Japan, vol. 1999, No. 14, Dec. 22, 1999.
Patent Abstracts of Japan, vol. 2000, No. 7, Sep. 29, 2000.
Krauth Wolfgang
Schwenk Wolfgang
Kenyon & Kenyon
Masih Karen
Robert & Bosch GmbH
LandOfFree
Method for starting a sensor- and brushless d.c. motor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for starting a sensor- and brushless d.c. motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for starting a sensor- and brushless d.c. motor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3204548