JPH11234988A - Three-phase motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized three-phase motor at a low cost in which a general-purpose driving circuit can be used similarly to an ordinary three- phase motor. SOLUTION: This three-phase motor 1 contains a first member 2 having salient-poles in three parts, and a second member 6 having magnets 8, 9 at positions facing each of the salient-poles 3, 4, 5. An U-phase coil Cu and a V-phase coil Cv are wound around the salient-poles 3, 4. A W-phase coil Cw is omitted. Specified currents are applied to the U-phase coil Cu and the V-phase coil Cv. The currents applied to the coils Cu and Cv are made equal to the values in which a current component to be applied to the omitted W-phase coil Cw is subtracted, i.e., Iu-Iw and Iv-Iw. The winding start part of the U- phase coil Cu is a first terminal i1, and the winding start part of the V-phase coil Cv is t2. A connection point formed by connecting the winding end portions of the coils is a third terminal t3. The terminals t1, t2 and t3 are connected with output terminals p1, p2 and p3 of a driving circuit 11, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a three-phase motor,
In particular, it relates to the driving circuit.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a conventional three-phase motor 31. The stator 32 shown in FIG.
There are salient poles 33, 34, 35 at locations. Each salient pole 33
The rotor 3 having the magnet 36 is located at a position facing
7 are arranged. The U-phase salient pole 33 has a U-phase coil Cu
However, the V-phase salient pole 34 has a V-phase coil Cv, and the W-phase salient pole 35
Is wound with a W-phase coil Cw. In such a three-phase motor 31, the coils Cu, Cv, C
AC currents having different phases are supplied to w. As a result, the rotor 37 rotates relatively to the stator 32. Here, FIG. 5B shows a general drive circuit 38 for driving the coils Cu, Cv, and Cw of each phase. The drive circuit 38 includes an inverter circuit including six transistors Tr, and the coils Cu, Cv, and Cw of each phase are so-called star-connected to the inverter circuit. That is, winding end portions of the phase coils Cu, Cv, and Cw are connected to each other. The winding start of the U-phase coil Cu is connected to the emitter-collector connection point of the U-phase transistor pair. The beginning of winding of the V-phase coil Cv is connected to the emitter-collector connection point of the V-phase transistor pair. The winding start portion of the W-phase coil Cw is connected to the emitter-collector connection point of the W-phase transistor pair.

[0003] In the field of three-phase motors, there are considerable demands for simplification of the manufacturing process and cost reduction. For this purpose, for example, three types of coils Cu,
It is considered that one of Cv and Cw may be omitted. However, simply reducing the number of coils from three to two has a high possibility that the driving performance of the motor 31 will be impaired, and has not actually been realized.

In this regard, the present inventor has proposed three types of coils Cu,
Despite omitting one of Cv and Cw, a three-phase motor 41 capable of exhibiting the same drive performance as a normal three-phase motor has been newly conceived. Here, a description will be given of how the three-phase motor 41 is conceived.

FIG. 6A shows a part of a conventional ordinary three-phase motor. Each of the three salient poles of the first member has three types of coils (U-phase coil Cu, V-phase coil Cv,
The W-phase coil Cw) is wound. In the figure, the white arrow φu indicates the direction of the magnetic flux passing through the U-phase coil Cu, φv indicates the direction of the magnetic flux passing through the V-phase coil Cv,
w represents the direction of the magnetic flux passing through the W-phase coil Cw.

Here, assuming that magnetic flux leakage from the first member is negligibly small, each coil C
For magnetic fluxes φu, φv, φw passing through u, Cv, Cw, the following equations 1 to 3 hold.

Φu = − (φv + φw) (1) φv = − (φu + φw) (2) φw = − (φu + φv) (3) That is, the magnetic flux passing through one specific coil is the other two. It can be understood that the relationship is equal to a value obtained by subtracting the sum of the magnetic fluxes passing through the coil.

Further, currents to be supplied to the coils Cu, Cv, Cw are denoted by Iu, Iv, Iw, respectively, and a second member (rotor) including the coils Cu, Cv, Cw and a magnet is provided.
Let θ be the relative rotation angle with respect to each coil Cu, C
The torques Tu, Tv, Tw generated by v and Cw are expressed by the following equations 4 to
It looks like 6.

Tu = (dφu / dθ) × Iu (4) Tv = (dφv / dθ) × Iv (5) Tw = (dφw / dθ) × Iw (6) Hereinafter, only the W-phase coil Cw is used. To continue with the example,
With respect to the torque Tw generated by the W-phase coil Cw, the following equation 7 can be derived from the equations 3 and 6.

Tw = − (dφu / dθ) × Iw− (dφv / dθ) × Iw (7) Here, the W-phase coil Cw, which is a specific type of coil, is a W-phase salient pole that should be originally provided. In this case, a configuration of the motor which is substantially equivalent to Equation 7 will be considered. In the motor shown in FIG. 6B, the W-phase coil Cw is not wound around the W-phase salient pole, the W-phase coil Cw1 is wound around the U-phase salient pole, and the W-phase salient pole is wound around the V-phase salient pole. The phase coil Cw2 is wound. W-phase coils Cw1, C
Since w2 is wound in the opposite direction to the U-phase coil Cu and the V-phase coil Cv, a current flows in the opposite direction. In such a motor, a current Iu is supplied to the U-phase coil Cu and a current Iv is supplied to the V-phase coil Cv.
And the current I is supplied to the W-phase coils Cw1 and Cw2, respectively.
If w is energized, the condition of Equation 7 can be satisfied,
Driving performance equivalent to that of a normal three-phase motor can be exhibited.

FIG. 6 (c) shows a configuration of a motor which has been further developed. In this motor, the W-phase coil Cw is
Not only are the salient poles omitted, but neither the U-phase salient pole nor the V-phase salient pole is wound. Instead, for the U-phase coil Cu not omitted, the current Iu-I obtained by subtracting the current that should be supplied to the omitted W-phase coil Cw.
w is energized. Further, a current Iv-Iw obtained by subtracting a current that should be supplied to the W-phase coil Cw is supplied to the V-phase coil Cv that is not omitted. Even with such a configuration, the condition of Expression 7 can be substantially satisfied, and a driving performance equivalent to that of a normal three-phase motor can be realized.

FIG. 7A shows a configuration example of a three-phase motor 41 embodied based on the above concept.
7 (b) and 7 (c) show a drive circuit 42 required to drive the motor 41. The drive circuit 42 includes a U-phase drive unit 43 for supplying an AC current to the U-phase coil Cu, and a V-phase drive unit 44 for supplying an AC current to the V-phase coil Cv. Each of these driving units 43 and 44 includes an inverter circuit composed of four transistors Tr.

[0013]

However, in the three-phase motor 41 in which one kind of coil Cw is omitted, it is not only necessary to use two extra transistors Tr than in the prior art, and the drive circuit 42 is not a general-purpose product. Had to be used separately. Therefore, the number of parts of the drive circuit 42 increases correspondingly, and a problem that the size of the entire apparatus and cost increase due to the increase in the number of parts is expected.

Even if a general-purpose drive circuit 38 consisting of six transistors Tr can be used,
It was sufficiently expected that the load applied to the transistor Tr of each phase would vary. Therefore, it was thought that some measures should be taken to eliminate this if the cost is to be further reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its main object to provide a small-sized and low-cost three-phase motor because a general-purpose drive circuit is sufficient as in a normal three-phase motor. Is to do.

It is a further object of the present invention to provide a three-phase motor in which loads applied to respective semiconductor elements constituting a general-purpose drive circuit are equal.

[0017]

In order to solve the above-mentioned problems, according to the present invention, a first member having salient poles at integer multiples of three and a position facing each of the salient poles are provided. A second member having a magnet, three types of coils wound around the salient poles, respectively, and a drive circuit using a plurality of semiconductor elements. Of the three types of coils in a normal three-phase motor in which both members move relative to each other.
Instead of omitting only one kind of coil, a current obtained by subtracting the current that should be originally applied to the one kind of omitted coil is applied to the other two kinds of coils which are not omitted. In the three-phase motor configured as described above, among the other two types of coils not omitted, the winding start portion of the first coil is a first terminal, and the winding start portion of the second coil is a second terminal. And a connection point formed by connecting the winding end portions of the two coils to each other as a third terminal, wherein each of the terminals is connected to three output terminals of the drive circuit. The gist is a motor.

According to a second aspect of the present invention, a first member having salient poles at integer multiples of three, a second member having magnets at positions opposed to the salient poles, and windings around the salient poles, respectively. An ordinary three-phase system including three types of coils to be turned and a drive circuit using a plurality of semiconductor elements, and when the coils are energized from the drive circuit, the two members move relative to each other. Of the three types of coils in the motor, only one specific type of coil is omitted.
A three-phase motor configured to supply a current, which is reduced by a current that should be originally supplied to the first coil, to the first coil among the other two coils not omitted.
A connection in which the winding start of the coil is a first terminal, the winding end of the second coil is a second terminal, and the winding end of the first coil and the winding start of the second coil are connected to each other. The gist of the present invention is a three-phase motor, wherein each point is a third terminal, and each of the terminals is connected to three output terminals of the drive circuit.

According to a third aspect of the present invention, in the first or second aspect, the driving circuit includes an inverter circuit including six transistors, and the three output terminals are connected to an emitter-collector connection of three pairs of transistors. It is said that it is provided at each point.

Hereinafter, the operation of the present invention will be described. According to the first aspect of the present invention, the first and second coils that are not omitted are each supplied with a current that is reduced by the amount of current that should be originally supplied to the one type of omitted coil. Is done. Even in this case, as described above, driving performance equivalent to that of a normal three-phase motor is realized. At this time, since the connection point formed by connecting the winding end portions of the two coils to each other is the third terminal, the number of terminals on the coil side is reduced by one. Therefore, each terminal can be connected to a drive circuit having three output terminals. Therefore, a general-purpose drive circuit is sufficient like a normal three-phase motor, and a small-sized and low-cost three-phase motor can be obtained.

According to the second aspect of the present invention, the first and second coils not omitted are reduced by the amount of current that should be supplied to the specific one kind of coil. Are respectively energized. Even in this case,
As described above, driving performance equivalent to that of a normal three-phase motor is realized. At this time, a connection point formed by connecting the winding end of the first coil and the winding start of the second coil to each other is connected to the third coil.
Since the terminals are used, the number of terminals on the coil side is reduced by one. Therefore, each terminal can be connected to a drive circuit having three output terminals. Therefore, a general-purpose drive circuit is sufficient like a normal three-phase motor, and a small-sized and low-cost three-phase motor can be obtained. Further, according to the present invention, a current having a reverse phase is applied to the second coil from a substantially opposite direction. Therefore, there is no change in the direction of the current itself, and the phase difference between the currents supplied from the output terminals of the drive circuit becomes 120 °. Therefore, only the load on the semiconductor element corresponding to the output terminal connected to the third terminal does not increase as compared with the other terminals. As described above, the loads applied to the respective semiconductor elements constituting the driving circuit are equalized, so that the cost can be further reduced.

According to the third aspect of the present invention, by conducting on / off operation by appropriately combining the six transistors constituting the inverter circuit, current is supplied to each coil from the emitter-collector connection point of the transistor pair,
As a result, the motor is reliably driven. Further, since this inverter circuit is a general-purpose product including six transistors, even if it is used, there is no problem that the whole device becomes large and the cost increases.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A three-phase servomotor 1 according to a first embodiment of the present invention will be described below in detail with reference to FIGS.

As shown in FIG. 1, a stator 2 as a first member constituting a three-phase servomotor 1 of the present embodiment
Is a metal member made of iron or the like, and has salient poles 3, 4, and 5 of the same shape at three places. U-phase salient pole 3, V
The phase salient poles 4 and the W phase salient poles 5 project in the radial direction of the stator 2 so as to form an angle of about 120 ° with each other. The tip of each salient pole 3, 4, 5 is formed in an arc shape and wide.

A rotor 6 as a second member constituting the three-phase servomotor 1 has a cylindrical yoke 7 and its yoke 7
And a plurality of permanent magnets 8 and 9 arranged on the inner peripheral surface of the main body. The first permanent magnet 8 has an N pole facing the stator 2 side, and the second permanent magnet 9 has an S pole facing the stator 2 side. Note that the first and second permanent magnets 8 and 9 are arranged every other one. A certain gap is secured between the inner surface of each of the permanent magnets 8 and 9 and the tip surface of each of the salient poles 3, 4 and 5 to avoid contact.

A U-phase coil Cu as a first coil is wound around the U-phase salient pole 3, and a V-phase coil Cv as a second coil is wound around the V-phase salient pole 4. Where W
As for the phase salient pole 5, the W-phase coil C which should be wound originally
w is not wound and omitted. Therefore, in the three-phase servomotor 1, the number of coils is two (that is, two).
And one type (ie, one) less than the normal one.

FIG. 2B shows a drive circuit 11 for driving the three-phase servomotor 1 of the present embodiment. Drive circuit 11 used in the present embodiment
Are six transistors Tr as a plurality of semiconductor elements.
1, and an inverter circuit 12 composed of Tr2, Tr3, Tr4, Tr5, and Tr6. The transistors Tr1 and Tr2 form a U-phase transistor pair, the transistors Tr3 and Tr4 form a V-phase transistor pair, and the transistors Tr5 and Tr6 form a W-phase transistor pair.

The collector terminals of the transistors Tr1, Tr3, Tr5 are all connected to the positive side of the power supply. The emitter terminals of the transistors Tr2, Tr4, Tr6 are all connected to the negative side of the power supply. A connection point between the emitter terminal of the transistor Tr1 and the collector terminal of the transistor Tr2 functions as a first output terminal p1. A connection point between the emitter terminal of the transistor Tr3 and the collector terminal of the transistor Tr4 functions as a second output terminal p2. A connection point between the emitter terminal of the transistor Tr5 and the collector terminal of the transistor Tr6 functions as a third output terminal p3.

An on-delay circuit (not shown) is connected to the base terminals of the transistors Tr1 to Tr6 of the inverter circuit 12. Each of the on-delay circuits has a SIN through a comparator (not shown).
Signals from a generation circuit (not shown) and a triangular wave generation circuit (not shown) are supplied. As a result, each transistor Tr1
To Tr6 are turned on and off at a predetermined timing.

In FIG. 2B, the side marked with a black circle is the winding start portion of each of the coils Cu and Cv. Two types of coils not omitted (ie, U-phase coil Cu and V-phase coil C)
v), the starting portion of the U-phase coil Cu is connected to the first terminal t.
1, and the winding start portion of the V-phase coil Cv is a second terminal t2. A connection point formed by connecting the winding end portions of the coils Cu and Cv to each other is referred to as a third terminal t3. The first terminal t1 is connected to the output terminal p1 by the second terminal t1.
2 is the output terminal p2, and the third terminal t3 is the output terminal p2.
3 are connected to each other.

Therefore, when the transistors Tr1 and Tr6 are on, the U-phase coil Cu has a current flowing downward in FIG. 2B, that is, a forward current flowing from the winding start portion to the winding end portion. Flows. Transistor Tr
2, when Tr5 is on, the U-phase coil Cu
A current flowing in the upward direction in (b), in other words, a current flows in the reverse direction from the winding end to the winding start.

When the transistors Tr3 and Tr6 are on, the V-phase coil Cv has a current flowing downward in FIG. 2B, that is, a forward current flowing from the winding start portion to the winding end portion. Flows. Transistor Tr4
, Tr5 are on, the V-phase coil Cv
A current flowing in the upward direction in (b), in other words, a current flows in the reverse direction from the winding end to the winding start.

A current feedback loop is formed by using a current detector (not shown) for detecting the current of the U-phase coil Cu and the V-phase coil Cv for each phase instead of the driving circuit 11 as shown in FIG. It is also possible to employ a drive circuit that has been used.

Here, it is assumed that the current that should be supplied to the W-phase coil Cw in the ordinary three-phase servomotor is Iw. In addition, U in the three-phase servomotor 1 of the present embodiment
Currents to be supplied to the phase coil Cu and the V-phase coil Cv are denoted by Iu ′ and Iv ′, respectively. Further, a current to be supplied to the W phase is defined as Iw ′.

The three-phase servomotor 1 is configured such that a current Iu 'corresponding to Iu-Iw is supplied to the U-phase coil Cu. That is, a current obtained by subtracting a current Iw, which should be originally supplied to the W-phase coil Cw, from the current Iu, which should be supplied to the U-phase coil Cu in the ordinary three-phase servomotor, is supplied. Become. Also, for the V-phase coil Cv, Iv-Iw
The current Iv ′ corresponding to is supplied. That is, from the current Iv that should be energized to the V-phase coil Cv in the ordinary three-phase servomotor, the current Iw that should be energized to the W-phase coil Cw in the same motor is changed.
Will be supplied.

FIG. 2A shows the currents Iu ', Iv', I
The temporal change of w ′ is shown for reference. According to this, the phase difference between the current Iu ′ and the current Iv ′ is 60
°, the phase difference between the current Iv ′ and the current Iw ′ is 150 °, and the phase difference between the current Iw ′ and the current Iu ′ is 150 °. Although the maximum values of the U-phase current Iu 'and the V-phase current Iv' are almost the same, only the maximum value of the W-phase current Iw 'is larger than them. Therefore, as the inverter circuit 12 in the present embodiment, it is necessary to select an inverter circuit having a standard capable of withstanding the load applied to at least the two transistors Tr5 and Tr6 constituting the W-phase transistor pair.

When the motor 1 is energized under the above-described conditions under the above-described configuration, the repulsive force or attractive force of the magnet acts between the rotor 6 and the stator 2, and the rotor 6 acts on the stator 2. Relative rotation smoothly.

Therefore, according to the present embodiment, the following effects can be obtained. (1) According to the three-phase servomotor 1, as described in detail above, the condition of the above-described equation (7) is substantially satisfied despite omitting one specific type of coil (here, the W-phase coil Cw). It is possible to meet. That is, it is possible to obtain an amount corresponding to the torque Tw that would have been generated by the W-phase coil Cw of the normal three-phase servomotor. Therefore, driving performance equivalent to that of a normal three-phase motor can be realized.

(2) According to the three-phase servo motor 1,
Since the W-phase coil Cw can be omitted, the number of coils needs to be one less than in the related art. Therefore, the motor 1 can be manufactured easily and at low cost. Further, with the above-described energization method, even when the number of current detectors, which was three, is reduced to two, the same drive performance as when the number of coils is three can be realized. Also, 2
If the current feedback control is performed based on the current detection results of the current detectors for the phases, it is not necessary to calculate the amount of current supplied to the W-phase coil Cw by calculation.
Therefore, the three-phase servomotor 1 that is less susceptible to disturbance due to noise and has a small vibration and smoothly rotates, that is, a three-phase servomotor 1 having excellent driving performance
Can be realized. In addition, unlike the conventional case, two current detectors are sufficient, so that the cost can be further reduced.

(3) In this embodiment, the U-phase coil Cu
And a connection point formed by connecting the winding end portions of the V-phase coil Cv to each other, as a third terminal t3. Therefore, the number of terminals on the coil side is reduced by one as compared with the motor configuration of FIG. 7 having four terminals on the coil side in total. Therefore, it is possible to connect the terminals t1, t2, and t3 to the drive circuit 11 having three output terminals p1, p2, and p3 without excess and deficiency, respectively. Therefore, as with a normal three-phase motor, six transistors Tr
A general-purpose drive circuit 11 composed of 1 to Tr6 is sufficient. Therefore, the number of parts of the drive circuit 11 increases,
The compact and low-cost three-phase motor 1 can be realized without requiring the drive circuit 11 separately. Second Embodiment Next, a three-phase servomotor 21 according to a second embodiment of the present invention will be described with reference to FIGS. Here, differences from the first embodiment will be mainly described, and the common points will be assigned the same member numbers only.

As shown in FIG. 3, the three-phase servo motor 21 has basically the same components as the motor 1 of the first embodiment. However, the winding direction of the V-phase coil Cv, which is the second coil, is opposite to that of the first embodiment. Therefore, as shown in FIG. 4 (b), the connection point formed by connecting the winding end of the U-phase coil Cu and the winding start of the V-phase coil Cv to each other is the third terminal t1. Different. The third terminal t3 is connected to the output terminal p3 of the inverter circuit 12.

Therefore, when the transistors Tr1 and Tr6 are turned on, the U-phase coil Cu has a current flowing downward in FIG. 4B, that is, a forward current flowing from the winding start portion to the winding end portion. Flows. Transistor Tr
2, when Tr5 is on, the U-phase coil Cu
A current flowing in the upward direction in (b), in other words, a current flows in the reverse direction from the winding end to the winding start.

When the transistors Tr3 and Tr6 are turned on, the V-phase coil Cv has a current flowing downward in FIG. 4B, that is, a current flowing in the reverse direction from the winding end to the winding start. Flows. Transistor Tr4
, Tr5 are on, the V-phase coil Cv
The current flowing in the upper direction in (b), in other words, the forward current flowing from the winding start to the winding end flows.

Here, the three-phase servo motor 2 of the present embodiment
Currents to be supplied to the U-phase coil Cu and the V-phase coil Cv in 1 are denoted by Iu ″ and Iv ″, respectively. Further, a current to be supplied to the W phase is defined as Iw ″. This 3
Also in the phase servo motor 21, a current Iu ″ corresponding to Iu-Iw is supplied to the U-phase coil Cu, and a current Iv ″ corresponding to Iv-Iw is supplied to the V-phase coil Cv.

FIG. 4A shows currents Iu ″, Iv ″, I
The state of the temporal change of w '' is shown for reference. According to this, the phase difference between the current Iu ″, the current Iv ″, and the current Iw ″ is greatly different from that of the first embodiment in that they are all 120 °. Further, only the maximum value of the current Iw ″ of the W phase is not larger than the others, and the maximum value of each phase is substantially the same. This means that the two transistors Tr5 and Tr6 forming the W-phase transistor pair
Is smaller than that of the first embodiment.

Therefore, according to the present embodiment, the following effects can be obtained in addition to the effects (1) and (2) of the first embodiment. (4) In this embodiment, the third terminal t3 is a connection point where the winding end of the U-phase coil Cu and the winding start of the V-phase coil Cv are connected to each other. Therefore, the number of terminals on the coil side is reduced by one as compared with the motor configuration of FIG. 7 having four terminals on the coil side in total. Therefore, it is possible to connect the terminals t1, t2, and t3 to the drive circuit 11 having three output terminals p1, p2, and p3 without excess and deficiency, respectively. Therefore, a general-purpose drive circuit 11 composed of six transistors Tr1 to Tr6 is sufficient as in a normal three-phase motor. Therefore, it is possible to realize a small-sized and low-cost three-phase motor 21 without increasing the number of components of the drive circuit 11 and without requiring the drive circuit 11 separately.

(5) Also, for the V-phase coil Cv as the second coil, a current Iv ″ substantially in the opposite direction from the opposite direction.
Will be energized. Accordingly, there is no change in the direction of the current Iv ″ itself, and the phase difference between the currents Iu ″, Iv ″, Iw ″ of each phase is also 120, as shown in FIG.
° and even. For this reason, the load on the two transistors Tr5 and Tr6 constituting the W-phase transistor pair is reduced, and thus each of the transistors Tr1 to Tr6 is reduced.
The load applied to the load becomes even. Therefore, the inverter circuit 1
It is not necessary to increase the specification of No. 2 in accordance with the maximum output peak of the transistors Tr5 and Tr6. as a result,
As compared with the case of the first embodiment, the inverter circuit 12 having a smaller standard can be selected, so that the cost can be further reduced.

The embodiment of the present invention may be modified as follows. ◎ Instead of the above-described embodiments in which the W-phase coil Cw is omitted,
A configuration in which the U-phase coil Cu is omitted, or
Of course, a configuration in which the phase coil Cv is omitted may be adopted.

The first embodiment is not limited to the above embodiments in which the first member side is used as the stator 2 (that is, the fixed side) and the second member side is used as the rotor 6 (drive side).
It is of course also permissible to use the member side as the drive side and the second member side as the fixed side.

The three-phase motor of the present invention is not only embodied as the rotary motors 1 and 21 as in each embodiment, but also as another type of motor such as a linear motor. Is also good.

The concept of the present invention can be applied not only to a three-phase motor but also to a four-phase, five-phase, six-phase, seven-phase, and eight-phase motor.
It can be applied to multi-phase motors such as phase, 9 phase, 10 phase...

Next, technical ideas other than the inventions described in the claims, which can be understood from each embodiment and other examples, will be described below together with their effects as necessary. (1) The stator according to any one of claims 1 to 3, wherein the first member is a stator having salient poles projecting radially from three places so as to form an angle of about 120 ° with each other. The two members are rotors in which magnets are arranged on an inner peripheral surface of a yoke provided to surround the stator, and the rotor performs relative rotation with respect to the stator by energizing the respective coils. Three-phase motor.

(2) In any one of the first to third aspects and the technical idea 1, the three-phase motor may include a current for detecting the current of the two coils not omitted for each phase. A three-phase motor having a detector and being a servomotor for performing feedback control based on a current detection result by the two-phase current detectors. Therefore, according to the invention described in the technical idea 2, since it is not necessary to obtain the amount of current supplied to the omitted third-phase coil by calculation, the influence of disturbance due to noise is reduced.

[0054]

As described above in detail, according to the first and third aspects of the present invention, a small-sized and low-cost three-phase motor can be provided because a general-purpose drive circuit is sufficient like a normal three-phase motor. Can be provided.

According to the second and third aspects of the present invention, a general-purpose drive circuit is sufficient as in the case of a normal three-phase motor. The load applied to each semiconductor element is equal 3
A phase motor can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a three-phase servo motor according to a first embodiment.

FIG. 2A is a graph showing a temporal change of each current supplied to the motor, and FIG. 2B is a schematic diagram for explaining a method of connecting a drive circuit and each phase coil in the motor. .

FIG. 3 is a schematic sectional view of a three-phase servo motor according to a second embodiment.

4A is a graph showing a temporal change of each current supplied to the motor, and FIG. 4B is a schematic diagram for explaining a method of connecting a drive circuit and each phase coil in the motor. .

FIG. 5A is a schematic sectional view of a conventional ordinary three-phase motor, and FIG. 5B is a schematic view for explaining a method of connecting a drive circuit and each phase coil in the motor.

FIGS. 6A and 6B are diagrams for explaining the process of conceiving a three-phase motor, in which FIG. 6A is a schematic diagram showing a main part of a normal three-phase motor, and FIGS. The schematic diagram which shows the principal part of the three-phase motor in which one kind of coil was omitted.

7A is a schematic cross-sectional view of a three-phase motor in which one kind of coil is omitted, FIG. 7B is a circuit diagram showing a U-phase drive unit of a drive circuit of the motor, and FIG. FIG. 3 is a circuit diagram illustrating a driving unit.

[Explanation of symbols]

1,21 ... 3-phase servo motor as 3-phase motor, 2, ...
Stator as a first member, 3, 4, 5, salient poles, 6 as rotor, 7 as yoke, 8, yoke, 8, 9 (permanent)
Magnet, 11 ... Drive circuit, 12 ... Inverter circuit, Cu ...
U-phase coil as first coil, Cv: V-phase coil as second coil, Cw: W-phase coil, Iu-Iw, Iv
-Iw: current obtained by subtracting a current that should be originally supplied to one of the omitted coils, t1 ... first terminal, t2 ... second terminal, t3 ... third terminal, p1, p2, p3 ... output terminals, T
r1 to Tr6: transistors as semiconductor elements.

Claims (3)

[Claims] 1. A first member having salient poles at integer multiples of 3, a second member having magnets at positions opposed to the salient poles, and three types of coils wound around the salient poles, respectively. And a drive circuit using a plurality of semiconductor elements, and the three types of coils in a normal three-phase motor in which both members relatively move by being energized from the drive circuit to each of the coils. Among them, instead of omitting only one specific type of coil, the amount of current that should be originally supplied to the one type of omitted coil is reduced with respect to the other two types of coils that are not omitted. A three-phase motor configured to be supplied with a current, wherein a winding start portion of a first coil is used as a first terminal and a winding start of a second coil is started, of the other two types of coils not omitted. Part as a second terminal, and furthermore, A three-phase motor, wherein each of the terminals is connected to three output terminals of the drive circuit, with a connection point formed by connecting winding end portions to each other as a third terminal. 2. A first member having salient poles at integer multiples of 3, a second member having magnets at positions opposed to the salient poles, and three kinds of coils wound around the salient poles, respectively. And a drive circuit using a plurality of semiconductor elements, and the three types of coils in a normal three-phase motor in which both members relatively move by being energized from the drive circuit to each of the coils. Among them, instead of omitting only one specific type of coil, the amount of current that should be originally supplied to the one type of omitted coil is reduced with respect to the other two types of coils that are not omitted. A three-phase motor configured to be supplied with a current, wherein a winding start portion of a first coil is a first terminal and a winding end of a second coil is an end of the other two types of coils not omitted. Part as a second terminal, and the first coil And a connection point formed by connecting a winding end portion of the second coil and a winding start portion of the second coil to each other as a third terminal, and the terminals are respectively connected to three output terminals of the drive circuit. Three-phase motor. 3. The drive circuit according to claim 1, wherein said drive circuit includes an inverter circuit comprising six transistors, and said three output terminals are provided at emitter-collector connection points of three sets of transistor pairs, respectively. 3. The three-phase motor according to 1 or 2.