Electricity: motive power systems – Synchronous motor systems – Hysteresis or reluctance motor systems
Reexamination Certificate
2000-02-14
2002-06-25
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Synchronous motor systems
Hysteresis or reluctance motor systems
C318S254100
Reexamination Certificate
active
06411060
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving of a switched reluctance motor (hereinafter, referred to as ‘SR motor’), and in particular to a driving device for an SR motor which can detect a position of a rotor of the SR motor by using a smaller number of sensors than phases, and which can drive the SR motor on the basis of the detected result.
2. Description of the Background Art
In order to exactly drive the SR motor, it is necessary to detect a position of a rotor of the SR motor. For this, sensors as many as phases are required. A speed of the rotor can be controlled by driving the rotor according to a result detected from the sensors.
For convenience' sake, a three phase SR motor will now be exemplified.
FIG. 1
is a circuit diagram illustrating a driving device of a conventional SR motor. Reference numeral
10
denotes a microprocessor,
20
denotes a switching mode power supply (hereinafter, referred to as ‘SMPS’),
30
denotes a driving circuit, and
40
denotes a position detection unit. The driving circuit
30
includes first to third driving units
31
,
32
,
33
. The first to third driving units
31
,
32
,
33
apply a current respectively to an A phase winding La, a B phase winding Lb and a C phase winding Lc of a stator of the motor. The position detection unit
40
includes first to third photo sensors Sa, Sb, Sc detecting a position of each phase of the rotor, and three switching transistors Q
7
, Q
8
, Q
9
corresponding to the operation of the three photo sensors Sa, Sb, Sc, and outputting a predetermined voltage (5V) to the first to third driving units
31
,
32
,
33
of the driving circuit
30
, respectively. On the other hand, a sensor disc with a slot (not shown) is inserted into the SR motor for the operation of the photo sensors Sa, Sb, Sc.
The operation of the conventional driving device for the SR motor will now be described.
The microprocessor
10
outputs a control signal to the SMPS
20
. The SMPS
20
outputs a direct current voltage having a predetermined level to the driving circuit
30
according to the control signal. The direct current voltage is converted by a capacitor C
1
and a resistance R
1
, and applied to the first to third driving units
31
,
32
,
33
. In this state, when the position of the rotor is detected by the position detection unit
40
, one of the first to third driving units
31
,
32
,
33
is operated according to the detected result. Accordingly, the current is applied to the A phase, B phase or C phase winding of the stator, thereby rotating the rotor.
For example, when the first photo sensor Sa is turned on, the switching transistor Q
7
is turned on. Thus, a voltage of 5V is applied to a lower switching transistor Q
4
of the first driving unit
31
. Accordingly, the lower switching transistor Q
4
is turned on, and an upper switching transistor Q
1
is also turned on, thus forming a current path consisting of the upper transistor Q
1
, the A phase winding of the rotor and the lower switching transistor Q
4
. The direct current voltage from the SMPS
20
is applied to the A phase winding La, and thus the rotor is rotated. When the rotor is rotated by a predetermined angle, the first photo sensor Sa is turned off, and the second photo sensor Sb is turned on. The switching transistor Q
8
is turned on by the On state of the second photo sensor Sb, and thus a lower switching transistor Q
5
and an upper switching transistor Q
2
of the second driving unit
32
are sequentially turned on. Accordingly, the direct current voltage from the SMPS
20
is applied to the B phase winding Lb of the stator, and thus the rotor is constantly rotated. On the other hand, a magnetic flux generated to the A phase winding La is removed by two free wheeling diodes D
1
, D
2
of the first driving unit
31
, thereby smoothly rotating the rotor.
The above-described position detection and driving steps are repeatedly performed, and thus the rotor is constantly rotated. On the other hand, in order to vary a rotation speed of the motor, the SMPS
20
may vary a level of the direct current voltage according to the control signal from the microprocessor
10
. The rotation speed of the rotor is varied according to the level of the direct current voltage.
However, the conventional driving device for the SR motor requires the position detection sensors such as the photo sensors as many as the phases in order to detect the position of each phase of the rotor. The position detection sensors are high priced. In addition, added is a step for installing the position detection sensors to the SR motor. In case any of the position detection sensors is out of order, the SR motor cannot be normally operated.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to drive a switched reluctance (SR) motor by using a smaller number of position detection sensors than phases.
In order to achieve the above-described object of the present invention, there is provided a driving device for a switched reluctance (SR) motor, including: a position detection unit for detecting a position of a rotor of the SR motor by using one position detection sensor; and a microprocessor for aligning the rotor by sequentially outputting a plurality of control signals at an initial stage of a starting of the SR motor, and for sequentially outputting the plurality of control signals according to a result detected from the position detection unit after starting the SR motor.
REFERENCES:
patent: 4739240 (1988-04-01), MacMinn et al.
patent: 4896088 (1990-01-01), Jahns
patent: 5532567 (1996-07-01), Iwasaki et al.
patent: 5563488 (1996-10-01), Stephenson et al.
patent: 5637972 (1997-06-01), Randall et al.
patent: 5652493 (1997-07-01), Hendershot, Jr.
patent: 5652494 (1997-07-01), Sugden
patent: 5737164 (1998-04-01), Ferreira et al.
patent: 5866962 (1999-02-01), Kim
patent: 6011377 (2000-01-01), Heglund et al.
patent: 6091170 (2000-07-01), Mayes et al.
patent: 08237982 (1996-09-01), None
patent: 10313588 (1998-11-01), None
patent: 10337073 (1998-12-01), None
patent: 11113276 (1999-04-01), None
patent: 11113283 (1999-04-01), None
English translation of Abstract of Japanese Patent Application No. 11113283 dated Apr. 23, 1999.
Duda Rina I.
LG Electronics Inc.
Ostrolenk Faber Gerb & Soffen, LLP
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