Electricity: motive power systems – Synchronous motor systems – Hysteresis or reluctance motor systems
Patent
1997-05-16
1999-01-26
Wysocki, Jonathan
Electricity: motive power systems
Synchronous motor systems
Hysteresis or reluctance motor systems
318254, H02P 700
Patent
active
058642188
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for controlling a reluctance motor.
BACKGROUND OF THE INVENTION
In the special embodiment with six stator teeth and four rotor teeth, the switched reluctance motor represents the most economical option for implementing a brushless drive. It was possible to reduce the drawback, which the motor had up until now, namely a high reactive power pulsation, to a small measure through special designs of the magnetic circuits of this motor. Novel circuit topologies became possible in the actuation electronics of this motor through the use of power circuit breakers.
These reasons and its extraordinary robustness predestine this drive principle for use in mass-manufactured products, in particular, in motor vehicles.
The physical principle of torque extraction of this motor type is based on the desire of a magnetic circuit permeated by a magnetic flux to minimize the magnetic resistance (or: reluctance) which is active in the circuit. If a rotor with a rotational angle-dependent magnetic resistance is disposed in a magnetic circuit, a rotational force is exerted upon the rotor if its rotation results in a reduction of the magnetic resistance.
FIG. 1 illustrates an exemplary course of the phase winding inductances of a three-phase reluctance motor having three phase windings, which motor has four rotor teeth and six stator teeth according to FIG. 2.
From IEE PROC., vo. 127B, no. 4, July, 1980, p. 25253-265: P. J. LAWRENSON ET AL. "Variable-speed switched reluctance motors", a calculation method for the behavior of a reluctance motor at a variable speed is known. Characteristic curves for the magnetic flux densities, currents and torques as a function of the rotational angle and of the angular velocity are indicated. A realization for circuit engineering is not indicated.
A microcomputer is used to retrieve the data regarding the switch-on course of the stator phases, which data are stored in a memory, and to therefrom match the switch-on angle and the pulse width of the current pulses switched in phases to the operating behaviors of the motor within certain limits. This matching of the pulse position and of the pulse duration makes it possible to obtain a large torque and speed range. At higher speeds, however, optimum matching can no longer take place in this simple manner. Therefore, towards higher speeds, the torque is reduced very quickly and the motor losses increase.
It is the object of the invention to set the switch-off angle for all operating states of the motor for a reluctance motor of the type described at the outset in such a way that a maximum output or torque yield is accomplished at a high efficiency and torque waviness as well as noise development are reduced.
This object is accomplished by a method for controlling a reluctance motor whose stator is provided with windings upon which, as a function of the angular position and the speed of rotation of the rotor, current pulses calculated according to a predetermined algorithm are impressed. Each winding phase excited according to a predetermined switch-on angle is switched off according to a switch-off angle (.gamma..sub.p) whose angular count starts with the inductance rise of the excited phase winding. Two operating ranges must be differentiated, which are identified as a "chop" range and a block voltage range.
For the method, the switch-off angle (.gamma..sub.p) for all operating ranges of the reluctance motor is calculated, from the actual value of the speed of rotation (n.sub.ist), the actual value of the supply voltage (u.sub.k), the minimum and maximum inductances (L.sub.min, L.sub.max) of a motor phase winding, and the value of the stator pole angle (.beta..sub.s). The minimum and maximum inductances (L.sub.min, L.sub.max) of a motor phase winding and the value of the stator pole angle (.beta..sub.s) are stored in a memory. The limit current (i.sub.G) is first determined from the product of the actual value of the supply voltage (u.sub.k) and the value of the stator pole angle (.beta..su
REFERENCES:
patent: 4739240 (1988-04-01), MacMinn et al.
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patent: 5168203 (1992-12-01), Tepavcevic
patent: 5783916 (1998-07-01), Blackburn
Bimal K. Bose et al.: "Microcomputer Control of Switched Reluctance Motor". In: IEEE Transactions of Industry Applications, vol. 1A-22, No. 4, Jul./Aug. 1986, pp. 708-715.
P.J. Lawrenson et al.: "Variable-speed switched reluctance motors". In: IEE Proc., vol. 127, Pt. B, No. 4, Jul. 1980, pp. 253-264.
J.W. Finch et al .: "Control aspects of brushless drives using switched reluctance motors". In: Proc. IEE, Conf. PEVD'90, London, pp.237-242.
J.T. Bass et al.: "Simplified Electronics for Torque Control of Sensorless Switched-Relectance Motor". In: IEEE Transactions on Industrial Electronics, vol. IE-34, No. 2, May 1987, pp. 234-239.
Daimler-Benz AG
Kunitz Norman N.
Spencer George H.
Wysocki Jonathan
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