Electricity: motive power systems – Switched reluctance motor commutation control
Patent
1987-01-23
1988-09-06
Ro, Bentsu
Electricity: motive power systems
Switched reluctance motor commutation control
318345H, H02P 600
Patent
active
047695811
DESCRIPTION:
BRIEF SUMMARY
The copending parent application Ser. No. 940,761, filed Nov. 4, 1986, concerns a circuit for controlling a brushless electric motor wherein a control voltage derived from the rotor position controls the supply of line voltage to the stator winding.
BACKGROUND OF THE INVENTION
The object of the invention in accordance with the parent application Ser. No. 940,761 is to create a circuit for controlling a brushless electric motor that allows the motor to run slowly independent of the line frequency.
This object is attained by the invention in accordance with the parent application in that the line voltage is supplied to the stator winding through a phase-control circuit and the polarity of the voltage supplied to the coil is always changed subsequent to a number of line periods.
This solution means that the frequency of the resulting rotary field can be essentially lower than the line frequency, allowing the motor to run more slowly than in the case of synchronous operation. The motor can then for example be employed in a washing machine to directly drive the drum in both rapid and slow operation.
The maximum motor speed is dictated by the line frequency, amounting to 3000 rpm in a single-pole embodiment for example. A higher speed is not directly possible with the circuitry in accordance with the parent application.
In practice, however, motors with a higher speed, 6000 to 9000 rpm for example, are often necessary.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the circuit in accordance with the parent application to the extent that the motor can also be driven at a speed higher than what corresponds to line frequency.
One line period is accordingly trimmed several times with the phase-control circuit in accordance with the invention. This measure alone does not lead to a higher speed. When, however, the current pulses obtained by phase control are supplied to the stator winding to generate opposite magnetic poles, a rotary field with a frequency higher than line frequency can be generated. The frequency of the resulting rotary field can for example then be two, three, or four times the line frequency. This means that the speed of the motor can be correspondingly higher than it would during synchronous operation at line frequency.
The current pulses obtained by phase trimming are supplied to the stator winding in such a way that, for example, currents of opposite polarity in the stator winding will generate similar magnetic poles, north for example, and currents of the same polarity will generate different poles, north and south that is. This is attained in accordance with one development of the invention in that the stator winding is divided into two oppositely poled subsidiary windings and current pulses are supplied alternately to the first subsidiary winding and second subsidiary winding. The magnetic poles are then reversed by means of the opposing polarity of the subsidiary winding.
In another development of the invention the stator winding is positioned along the diagonals a-b of a bridge that is fed with line voltage and has four controllable switches, especially triacs, in its branches. A circuit of this type can be employed to repole the direction of the current in the winding by igniting diagonally opposite switches. In this case it is unnecessary to divide the winding into two subsidiary windings.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be specified with reference to the drawings, wherein
FIG. 1 is a circuit diagram illustrating the principle behind the circuit in accordance with the invention,
FIG. 2 is a graph of the circuitry in FIG. 1,
FIG. 3 illustrates a further development of the circuitry in FIG. 1, and
FIG. 4 illustrates an example of how the stator winding can be controlled with a bridge circuit.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a stator winding S1 divided into two oppositely poled subsidiary windings S1a and S1b connected to line voltage UN by two triacs T1 and T2 controlled by phase control circuit Z wh
REFERENCES:
patent: 3470436 (1969-09-01), Steele
patent: 3564372 (1971-02-01), Vogelsberg et al.
patent: 3959709 (1976-05-01), Irish
patent: 4039915 (1977-08-01), Kofink
patent: 4238719 (1980-12-01), Bourbeau
patent: 4431958 (1984-02-01), Schutten et al.
Deutsche Thomson-Brandt GmbH
Fogiel Max
Ro Bentsu
LandOfFree
Circuit for controlling a brushless electric 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 Circuit for controlling a brushless electric motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Circuit for controlling a brushless electric motor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1608416