Electricity: motive power systems – Synchronous motor systems – Armature winding circuits
Reexamination Certificate
2001-03-07
2002-06-04
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Synchronous motor systems
Armature winding circuits
C318S254100
Reexamination Certificate
active
06400118
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a magnetic-pole position detecting apparatus for a synchronous motor capable of detecting a magnetic-pole position of a synchronous motor easily, securely and with high precision.
BACKGROUND ART
In order to efficiently control a synchronous motor, it has been a conventional practice to detect magnetic-pole positions of a rotor of the synchronous motor. As a method for detecting a magnetic-pole position of the synchronous motor, there has been a method of directly detecting an electric angle (a magnetic-pole position) of the rotor by using a position detector, like an encoder. However, in order to detect directly a rotation angle of the rotor, it is neccessary to add to the synchronous motor a sensor exclusively used for detecting a magnetic-pole position, like a position detector. This has drawbacks in that the scale of the apparatus becomes large which further leads to unsatisfactory economics of the apparatus.
Therefore, there has been proposed an apparatus that detects a magnetic-pole position of a synchronous motor without using a position detector (reference Japanese Patent Application (Laid-Open) No. 7-177788).
FIG. 24
is a diagram showing a schematic configuration of a conventional magnetic-pole position detecting apparatus for a synchronous motor that does not use a position detector. In
FIG. 24
, a synchronous motor
1
has a permanent-magnet type rotor, and has a three-phase winding of U-phase, V-phase and W-phase. An arithmetic section
102
outputs a voltage vector command V to a circuit section
3
, and outputs a trigger signal Tr to a detection section
4
. The circuit section
3
applies a voltage to each phase of the synchronous motor
1
based on the input voltage vector command V. The detection section
4
detects a current of each phase at a rise timing of the trigger signal Tr, and outputs a detection current Di to the arithmetic section
102
. The arithmetic section
102
calculates a magnetic-pole position &thgr; of the rotor based on the input detection current Di, and outputs a calculated result.
FIG. 25
is a diagram showing a detailed structure of the circuit section
3
. In
FIG. 25
, the circuit section
3
has semiconductor switches
5
to
10
. Each pair of semiconductor switches
5
and
8
,
6
and
9
, and
7
and
10
respectively are connected in series. Each pair of semiconductor switches
5
and
8
,
6
and
9
, and
7
and
10
respectively are connected in parallel with a DC voltage source
11
that generates a phase potential Ed. An intermediate point Pu for connecting between the semiconductors
5
and
8
is connected to the U-phase of the synchronous motor
1
. An intermediate point Pv for connecting between the semiconductors
6
and
9
is connected to the V-phase of the synchronous motor
1
. An intermediate point Pw for connecting between the semiconductors
7
and
10
is connected to the W-phase of the synchronous motor
1
. Each of the semiconductor switches
5
to
10
has a corresponding one of insulation gate type bipolar transistors (IGBT) Q
1
to Q
6
and a corresponding one of diodes D
1
to D
6
connected in parallel. The diodes are directed in sequence to a plus side of the DC voltage source
11
. Agate signal to be applied to a gate of each of the IGBTs Q
1
to Q
6
forms a voltage vector command V, and this voltage vector command V turns off/off corresponding transistors of the IGBTs Q
1
to Q
6
.
The voltage vector V has nine switching modes “0” to “8”, and the respective switching modes “0” to “8” are defined as follows based on combinations of the IGBTs Q
1
to Q
6
to be turned on.
Switching mode: Combination of the IGBTs Q
1
to Q
6
to be turned on
“0”: Nil
“1”: Q
1
, Q
5
, Q
6
“2”: Q
1
, Q
2
, Q
6
“3”: Q
4
, Q
2
, Q
6
“4”: Q
4
, Q
2
, Q
3
“5”: Q
4
, Q
5
, Q
3
“6”: Q
1
, Q
5
, Q
3
“7”: Q
1
, Q
2
, Q
3
“8”: Q
4
, Q
5
, Q
6
Voltage vectors V
1
to V
8
corresponding to the switching modes “1” to “8” have phase differences of 60 degrees respectively, with equal sizes as shown in
FIG. 26. A
size of the voltage vector V
1
will be obtained here, as one example. As the voltage vector V
1
corresponds to the switching mode “1”, the IGBTs Q
1
, Q
5
and Q
6
are turned on, and the IGBTs Q
4
, Q
2
and Q
3
are turned off. Therefore, a line voltage Vuv between the U-phase and the V-phase, a line voltage Vuv between the V-phase and the W-phase, and a line voltage Vwu between the W-phase and the U-phase are given by the following equations (1) to (3) respectively.
Vuv=Vu−Vv=Ed
(1)
Vvw=Vv−Vw=
0 (2)
Vwu=Vw−Vu=−Ed
(3)
where, “Vu” represents a phase of the U-phase (a potential of the intermediate point Pu), “Vv” represents a phase of the V-phase (a potential of the intermediate point Pv), and “Vw” represents a phase of the W-phase (a potential of the intermediate point Pw).
Further, from the equations (1) to (3), the potentials Vu to Vw are obtained as given by the following equations (4) to (6) respectively.
Vu=
⅔
*Ed
(4)
Vv=−
⅓
*Ed
(5)
Vw=−
⅓
*Ed
(6)
Therefore, a direction of the voltage vector V
1
becomes the direction of the U-phase as shown in FIG.
26
. Further, a size |V
1
| of the voltage vector V
1
is expressed as given by the following equation (7).
|V
1
=⅔
*Ed
−⅓
*Ed
cos(120 degrees)−⅓
*Ed
cos(240 degrees)=
Ed
(7)
Directions and sizes of other voltage vectors V
2
to V
6
can be obtained by carrying out similar calculations to those of the voltage vector V
1
. As shown in
FIG. 26
, directions of the voltage vectors V
2
to V
6
have phase differences of 60 degrees respectively sequentially from the U-phase, and their sizes become Ed. Further, the voltage vector V
7
and V
8
become voltage vectors having sizes 0 respectively as shown in FIG.
26
.
Voltages corresponding to these voltage vectors V
1
to V
6
are applied to the U-phase, the V-phase and the W-phase of the synchronous motor
1
respectively. In this case, thedetection section
4
detects a current that flows through each phase at the rise timing of the trigger signal Tr.
FIG. 27
is a block diagram showing a detailed structure of the detection section
4
. In
FIG. 27
, current detectors
12
to
14
detect currents that flow through the U-phase, the V-phase and the W-phase respectively, and output the detection currents to output processing sections
15
to
17
respectively. The output processing sections
15
to
17
have sample holding circuits
15
a
to
17
a
and A/D converters
15
b
to
17
b
respectively. The sample holding circuits
15
a
to
17
a
hold samples of the current values detected by the current detectors
12
to
14
respectively at the rise timing of the trigger signal Tr input from the arithmetic section
102
. The A/D converters
15
b
to
17
b
convert analog signals held by the sample holding circuits
15
a
to
17
a
into digital signals respectively, and output a current iu of the U-phase, a current iv of the V-phase, and a current iw of the W-phase respectively, which are collectively output as a detection current Di to the arithmetic section
2
.
A relationship between the voltage vector command V, the trigger signal Tr and the detection current Di will be explained next with reference to a timing chart shown in FIG.
28
. In
FIG. 28
, the arithmetic section
102
first sequentially outputs voltage vectors V
0
, V
1
, V
0
, V
3
, V
0
, V
5
, and V
0
in this order to the circuit section
3
as the voltage vector command V, when the synchronous motor
1
is in the halted state and also when the current of each phase is zero. At the same time, the arithmetic section
102
outputs the trigger signal Tr to the detection section
4
immediately after finishing the application of each voltage vector. As explained above, the circuit section
3
sequentially applies the voltage vectors V
0
, V
1
,
Kaitani Toshiyuki
Kinpara Yoshihiko
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
Ro Bentsu
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