Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
2001-02-15
2004-03-02
Lockett, Kimberly (Department: 2837)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C318S701000, C318S799000
Reexamination Certificate
active
06700348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method of driving a single-phase switched reluctance motor, and more particularly to a single-phase switched reluctance motor (SRM) driving apparatus and method which enables a high-speed and high-efficiency SRM by employing a plurality of sensors, and which can minimize the switching frequency of elements constituting an SRM driving section.
2. Description of the Related Art
A switched reluctance motor (SRM) is a specific type motor combined with a switching control device, wherein both its stator and rotor have a protruded pole type structure, and there exists no winding or permanent magnet of any type on the rotor part, enabling the SRM to have a very simple structure.
Since the SRM has a very simple structure, it has advantages in productivity. Also, it has a good starting characteristic and a great torque, while it requires little maintenance and repair such as a periodic exchange of brushes and so forth. Also, the structure of its driving apparatus is simplified in comparison to an induction motor driven by an inverter, and it has superior characteristics in torque per volume, efficiency, rating of the converter, etc.
Due to such superior characteristics, the SRM has been increasingly used in various fields in many countries.
FIG. 1
is a block diagram of a conventional single-phase SRM driving apparatus.
Referring to
FIG. 1
, the conventional single-phase SRM driving apparatus comprises a smoothing circuit section
102
for smoothing an AC current applied from a commercial AC power supply
101
to a DC voltage, a microcomputer
106
, a motor driving section
103
for receiving the DC voltage supplied from the smoothing circuit section
102
and a control signal outputted from the microcomputer
106
, and driving a motor
104
accordingly, and a Hall sensor
105
for detecting the position and speed of the motor
104
, and outputting a detection signal to the microcomputer
106
.
The operation of the conventional single-phase SRM driving apparatus as constructed above will be explained in detail with reference to FIG.
1
.
The smoothing circuit section
102
smoothes the input voltage of the commercial power supply
101
. The smoothed voltage is supplied to the motor driving section
103
, and the motor driving section
103
supplies the voltage to the motor
104
in accordance with the control signal from the microcomputer
106
.
Then, the Hall sensor
105
detects the rotating speed and phase of the motor
104
to generate a detection signal, and the microcomputer
106
controls the motor driving section
103
in accordance with the signal generated by and received from the Hall sensor
105
, so that the motor driving section
103
controls the voltage supplied to the motor
104
.
FIG. 2
is a view illustrating the construction of the conventional single-phase SRM and motor driving section.
Referring to
FIG. 2
, the conventional single-phase SRM motor
300
is a single-phase 6/6-pole SRM composed of a stator
207
, a rotor
208
, a magnet
209
for position detection, and a parking magnet
210
.
The conventional SRM driving section
200
comprises a DC link capacitor
201
for smoothing the AC power supply and outputting a smoothed DC voltage, upper and lower switching elements
202
and
203
, connected in parallel to the DC link capacitor
210
, for being turned on/off in accordance with a gate driving signal from a switching driving section (not illustrated) which rotates the motor in a forward or backward direction in accordance with a rotor position signal of the SRM, a first diode
204
connected to motor windings
206
for generating a torque according to an on/off operation of the upper and lower switching elements
202
and
203
, one terminal of the upper switching element
202
, and one terminal of the lower switching element
203
, and a second diode
205
connected between the other terminal of the upper switching element
202
and the other terminal of the lower switching element
203
.
The operation of the conventional single-phase SRM as constructed above will be explained in detail.
First, if the AC power supply is applied, the DC link capacitor
201
smoothes it to a DC voltage. This smoothed DC voltage is supplied to the motor windings
206
in accordance with the switching operation of the upper and lower switching elements
202
and
203
.
Specifically, the upper and lower switching elements
202
and
203
are turned on according to the position of the rotor
208
and the stator
207
of the SRM, and this causes a current path is formed through the DC link capacitor
201
, upper switching element
202
, motor windings
206
, and lower switching element
203
. Accordingly, a voltage is excited in the motor windings
206
, a magnetic force is generated from the stator
207
, and thus the SRM rotates by the magnetic force acting on the rotor
208
.
If the upper and lower switching elements
202
and
203
are simultaneously turned off as the SRM rotates, a phase current being applied to the motor windings
206
is eliminated through the first diode
204
, motor windings
206
, second diode
205
, and DC link capacitor
201
.
As described above, the conventional SRM is driven by supplying or intercepting the voltage to the motor in accordance with the on/off operation of the upper and lower switching elements
203
and
204
which constitute the motor driving section.
Here, the control signal applied to the upper and lower switching elements
202
and
203
is generated by detecting the rotating speed and the phase of the motor through the Hall sensor as shown in
FIG. 1
, and the microcomputer pulse-width-modulates the output signal of the Hall sensor and controls the on/off operation of the upper and lower switching elements
202
and
203
in accordance with a duty ratio of pulse width modulation (PWM).
FIG. 3
is a graph illustrating an inductance profile according to the phase change of the conventional single-phase SRM.
Hereinafter, the voltage supplying operation of the motor driving section to the motor will be explained in detail with reference to
FIGS. 2 and 3
.
According to the SRM having the structure as shown in
FIG. 2
, when a protruded pole part
207
-
1
of the stator
207
and a protruded pole part
208
-
1
of the rotor
208
are in an alignment state, the inductance of the SRM becomes greatest, while when they are in a misalignment state, the inductance becomes smallest.
Also, in the case of the conventional SRM having the 6/6-pole structure, the maximum point and the minimum point of inductance alternately appear every phase of 30°.
In order to drive the SRM, the Hall sensor (not illustrated) detects the position of the rotor
207
, generates and outputs the control signal to the microcomputer when a position a of the rotor
207
moves to a position b or b′ of the stator
208
, i.e., at the time point when the inductance increases. Then, the microcomputer generates the control signal, and supplies the current to the motor windings
206
by controlling the motor driving section to supply the voltage.
FIGS. 4
a
and
4
b
are views illustrating a normal parking position and an abnormal position of the single-phase SRM.
When the SRM is stopped, it is parked by mutual attraction acting between an N pole of a parking magnet
401
a
and an S pole of a magnet
404
a
fixed to a rotor
402
a
, and between an S pole of the parking magnet
401
a
and an N pole of the magnet
404
a
, respectively, as shown in
FIG. 4
a
, and thus a normal parking state of the SRM is maintained for the next rotation.
However, as occasion requires, when a rotor
402
b
is stopped, the SRM may be parked by mutual repulsion acting between an N pole of a magnet
404
b
fixed to the rotor
402
b
and an N pole of a parking magnet
401
b
, and between an S pole of the magnet
404
b
and an S pole of the parking magnet
401
b
, respectively, and this causes the SRM to be in an abnormal parking state.
As described above, the conventional single-phase SRM
Colon-Santana Eduardo
LG Electronics Inc.
Lockett Kimberly
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