Electricity: motive power systems – Synchronous motor systems – Hysteresis or reluctance motor systems
Reexamination Certificate
2001-03-23
2002-07-02
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Synchronous motor systems
Hysteresis or reluctance motor systems
C318S700000, C318S713000, C318S715000
Reexamination Certificate
active
06414462
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a speed control apparatus for a synchronous reluctance motor, and more particularly to a speed control apparatus for a synchronous reluctance motor which can accurately control the rotating speed of the motor, in accordance with a variation in load, without using any sensor adapted to detect the position of a rotor included in the motor.
2. Description of the Related Art
A synchronous motor, which is a kind of an AC motor, is a constant-speed motor which rotates at a fixed speed, irrespective of the load applied thereto at a certain frequency, that is, at a synchronous speed. In particular, in a synchronous reluctance motor, torque is generated, based on reluctance components. Accordingly, the rotation of the rotor included in the synchronous reluctance motor results from only a reluctance torque.
FIG. 1
is a plan view schematically illustrating a configuration of a conventional three-phase synchronous reluctance motor.
Referring to
FIG. 1
, the conventional three-phase synchronous reluctance motor, which is denoted by the reference numeral
100
, includes a stator
101
adapted to create a rotating magnetic field upon receiving an AC voltage applied thereof, and a rotor
102
arranged inside the stator
101
and adapted to rotate by virtue of the rotating magnetic field created by the stator
101
.
As shown in
FIG. 2
, the rotor
102
is divided into four regions each formed with grooves
102
h
. The grooves
102
h
of each rotor region are symmetrical with those of a facing one of the remaining rotor regions. The grooves
10
h
are adapted to generate an increased difference between a reluctance generated in a d-axis direction and a reluctance generated in a q-axis direction, thereby generating a reluctance torque for rotating the rotor
102
. In
FIG. 2
, the reference numeral
102
f
denotes a flow of magnetic flux generated by virtue of the magnetic field created by the stator
101
.
FIG. 3
is a block diagram schematically illustrating a conventional speed control apparatus applied to a three-phase synchronous reluctance motor having the above-mentioned configuration.
As seen in
FIG. 3
, the conventional speed control apparatus includes a speed controller
301
for receiving a deviation between a speed command value outputted from a main control unit (not shown) and an actual speed of the three-phase synchronous reluctance motor
310
detected by a rotor position detector
309
. The speed controller
301
controls the speed of a rotor
102
included in a synchronous reluctance motor
310
based on the speed deviation. The speed control apparatus also includes a magnetic flux command generator
305
for receiving an output signal from the rotor position detector
309
and computing a magnetic flux angle of the rotor
102
based on the received output signal.
The speed control apparatus also includes a magnetic flux angle operator
307
for receiving an output signal from the rotor position detector
309
, thereby computing a magnetic flux angle of the rotor; a coordinate converter
308
for conducting a coordinate conversion of a three-phase current inputted to the synchronous reluctance motor
310
into a two-phase; and a magnetic flux controller
306
for receiving an output signal from the magnetic flux command generator
305
and an output from the coordinate converter
308
, thereby controlling a magnetic flux-related current.
The speed control apparatus further includes a current controller
302
for receiving a deviation between an output signal from the speed controller
301
and the output signal from the coordinate converter
308
, along with an output signal from the magnetic flux controller
306
, thereby generating a torque-related voltage command and a magnetic flux-related command. The speed control apparatus also includes a voltage generator
303
for receiving the torque-related voltage command and magnetic flux-related command outputted from the current controller
302
and the output signal from the magnetic flux angle operator
307
, thereby outputting a three-phase voltage command. An inverter
304
receives the three-phase voltage command from the voltage generator
303
and supplies an AC voltage corresponding to the received three-phase voltage command to the three-phase synchronous reluctance motor
310
.
In the conventional speed control apparatus having the above-mentioned configuration, the speed controller
301
receives a deviation between a speed command outputted from the main control unit (not shown) and a speed value of the three-phase synchronous reluctance motor
310
fed back from the rotor position detector
309
. The speed controller
301
then outputs a current command i
qs
* relating to a torque in the q-axis direction of a rotating coordinate system, based on the received speed deviation.
The magnetic flux command generator
305
detects a positive torque range and a positive output range from the output signal from the rotor position detector
309
, thereby outputting a current command i
ds
* relating to magnetic flux in the d-axis direction of the rotating coordinate system. The magnetic flux controller
306
receives a deviation between the magnetic-flux-related current value i
ds
* outputted from the magnetic flux command generator
305
, and a two-phase-converted magnetic-flux-related current value i
ds
outputted from the coordinate converter
308
, thereby controlling a magnetic-flux-related current.
The magnetic flux angle operator
307
receives the output signal from the rotor position detector
309
, thereby computing a magnetic flux angle {circumflex over (&thgr;)} of the rotor. Based on the magnetic flux angle {circumflex over (&thgr;)}, the coordinate converter
308
conducts a coordinate conversion for a three-phase current inputted to the synchronous reluctance motor
310
into a two-phase, that is, a q and d-axis phase.
The current controller
302
receives the torque-related current command i
qs
* and the magnetic-flux-related current command i
ds
*, and generates a torque-related voltage command V
qs
* and a magnetic-flux-related voltage command V
ds
*, respectively. The torque-related voltage V
qs
*, and magnetic-flux-related voltage commands V
ds
*, are applied to the voltage generator
303
, which also receives the magnetic flux angle {circumflex over (&thgr;)} from the magnetic flux angle operator
307
. Based on these received signals, the voltage generator
303
outputs three-phase voltage commands V
as
, V
bs
, and V
cs
. The inverter
304
then applies a corresponding voltage to the synchronous reluctance motor
310
based on the three-phase voltage commands V
as
, V
bs
, and V
cs
.
In a speed control apparatus according to the above-mentioned conventional synchronous reluctance motor, a sensor such as an encoder or a hall IC is used for the rotor position detector
309
and adapted to obtain information about the position of the rotor. However, there are various technical difficulties with an application of such a sensor to refrigerators or air conditioners.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above mentioned problems, and an object of the invention is to provide a speed control apparatus for a synchronous reluctance motor which can accurately control the rotating speed of the motor by detecting only the current and voltage of each phase flowing in the motor without using any separate sensor that is necessarily adapted to detect the position of a rotor included in the motor.
These and other objects are accomplished by a speed control apparatus for a synchronous reluctance motor comprising a voltage detector for detecting a voltage applied to the synchronous reluctance motor; a first phase converter for receiving voltages in three phases outputted from the voltage detector based on the voltage detection thereof, and converting the three-phase voltages into equivalent voltages in two phases; a current detector for detecting a current applied to the synchronous reluctance moto
Leykin Rita
LG Electronics Inc.
Nappi Robert E.
LandOfFree
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