Electricity: motive power systems – Synchronous motor systems – Hysteresis or reluctance motor systems
Patent
1990-10-01
1992-01-28
Shoop, Jr., William M.
Electricity: motive power systems
Synchronous motor systems
Hysteresis or reluctance motor systems
318696, 318811, 318599, 318685, G05B 1940
Patent
active
050846639
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a control arrangement for a reluctance motor of the kind indicated in the preamble of appending claim 1.
In particular, the arrangement is intended to be used in connection with a reluctance motor having a four-pole stator and a two-pole rotor and being described more in detail in the appending description of a preferred embodiment. In the embodiment chosen, the motor comprises a stator in which the four poles are arranged so as to form a cross. The rotor is shaped such that its poles are being disposed diametrically opposite each other. In the usual way, the stator poles have windings while the rotor is made of soft-magnetic material, without any windings. The rotor poles have got a shape and extend so as to have one part of it completely covering a stator pole while, at the same time, having another part of it filling up the space to the adjacent stator pole, as seen in the direction of rotation. The latter part of the rotor pole has a greater air gap than the first-mentioned part.
In the 4/2-pole motor, referred to, the stator poles are being activated in pairs twice during each revolution. The stator pole windings thus activated create a magnetic field which is directed in parallel to one or the other of the pole pairs. When the magnetic field is set up, the rotor is forced to take the position where the magnetic resistance, or reluctance, has its minimum value in the magnetic circuit. In this minimum reluctance position the rotor is disposed such that its poles coincide with the activated stator poles. When the rotor poles are aligning with the stator poles a sensor emits to a control arrangement for the motor a signal operating it to throw over and to activate the other pair of stator poles. When the rotor pole is aligned with the poles of a stator pole pair, that part of the rotor pole having the greater air gap, called the starting pole, is disposed such that it can create torque with one of the poles of the other stator pole pair. The function of the said starting pole is to ensure torque for driving of the rotor in all positions of the same. However, the starting pole also brings with it that the motor can only rotate in a single direction.
One problem related to reluctance motors of the kind referred to is that at higher motor speeds the magnetic field will not have sufficient time to build up to generate the required torque. The solution to the problem is to activate the stator windings prior to the sensor indicating the alignment of the rotor and stator poles.
The problem at high motor speeds, referred to, is primarily connected with the desire of providing sufficient torque when, at the same time, the motor is highly loaded and rotates at a high speed. The object of the invention is to solve this problem and to provide an arrangement which in dependence on the actual torque demand controls the time of preactivation of a pair of stator poles. The object is achieved by an arrangement in accordance with appending claim 1. Preferred embodiments appear from the sub-claims connected therewith.
The invention will now be described in detail in connection with an embodiment, with reference to the enclosed drawings, in which
FIG. 1 schematically shows a reluctance motor having four stator poles and two rotor poles,
FIG. 2 schematically shows the directions of magnetic flux in the motor according to FIG. 1,
FIG. 3 is a block diagram of a control arrangement for the motor of FIG. 1,
FIG. 4a,b,c, are identical circuit diagrams for different operating situations concerning the part of the control arrangement supplying current to the stator pole windings of the motor,
FIG. 5 is a circuit diagram of a power supply unit being part of the control arrangement,
FIG. 6 is a circuit diagram of circuits for current sensing and for generating of a current limit signal, respectively,
FIG. 7 is a principal circuit diagram showing the generation of a rotor position signal,
FIG. 8 is a circuit diagram of circuits for generating of a sawtooth voltage based on the rotor position signal,
FI
REFERENCES:
patent: 3679953 (1972-07-01), Bedford
patent: 4684867 (1987-08-01), Miller et al.
patent: 4746843 (1988-05-01), Taenzer
patent: 4760316 (1988-07-01), Hedlund
patent: 4990843 (1991-02-01), Moren et al.
Aktiebolaget Electrolux
Bergmann Saul M.
Shoop Jr. William M.
LandOfFree
Control arrangement for a reluctance 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 Control arrangement for a reluctance motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control arrangement for a reluctance motor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1862977