JP3413816B2 - Synchronous motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor which is self-starting as an induction motor and switches to synchronous operation.

[0002]

2. Description of the Related Art A general synchronous motor includes a starter for accelerating its rotor up to a rotational speed of a rotating magnetic field formed by a stator winding, that is, a synchronous speed, and a brush and a DC for exciting the rotor winding by direct current. Power is needed.

An induction synchronous motor is one in which the synchronous motor itself is provided with a starting torque by omitting the starter. This does not require a starter to short-circuit the rotor winding at start-up and start it as an induction motor, but does require a brush for DC excitation of the rotor winding required for synchronous operation. That is, when the rotation speed of the rotor approaches the synchronous speed, the short circuit of the rotor winding is released, and a DC current is passed from the external DC power source to the rotor winding through the brush to form a magnetic pole on the rotor. This magnetic pole is pulled by the rotating magnetic field created by the stator windings, and the rotor rotates at a synchronous speed. However,
Since this brushed electric motor requires maintenance and inspection, the maintenance cost is high, and a synchronous electric motor having a brushless structure and capable of self-starting is desired.

As a brushless synchronous motor having a structure having a rotor winding, there is a brushless synchronous motor with an AC exciter using an AC exciter and a rotary rectifier, but this has a drawback that the circuit configuration is complicated and the reliability is low. is there. There is also a brushless self-excited three-phase synchronous motor that connects a diode to the rotor winding and uses the harmonic magnetic field generated by the square wave voltage of the inverter. There is a drawback that sufficient output cannot be obtained because the field magnetomotive force of the child is insufficient.

Further, in the above-mentioned inverter-driven brushless synchronous motor, a diode is connected to one phase of the three-phase stator winding.
The static magnetic field generated by the stator is superposed on the rotating magnetic field for the positive phase to induce an AC voltage due to the static magnetic field in the rotor winding rotating near the synchronous speed, and this is rectified by the diode. By doing so, there is a brushless self-excited three-phase synchronous motor that excites the rotor winding by direct current and applies a rotating magnetic field for the positive phase to generate synchronous torque.However, since this is also impossible to start the induction machine, There is a drawback that the starting torque is small due to the eddy current of the rotor core, and the synchronizing torque is also small.

The applicant of the present application has disclosed an induction synchronous motor having a plurality of stators in order to solve these drawbacks of the prior art in Japanese Patent Laid-Open No. 212143/1993.

[0007]

In this synchronous motor, rotor windings wound around a plurality of rotor cores provided on the same rotary shaft are connected in parallel, and the terminals of the rotor windings are connected to each other. It is composed of a rotor to which a diode is connected, a stator winding, and a plurality of stators in which a DC exciting circuit including a DC exciting winding is provided in one phase of the stator winding.

In the DC excitation circuit of this synchronous motor, an AC voltage of the fundamental wave is generally induced by the rotating magnetic field of the stator winding. This is because the AC voltage of the excitation winding induced by the fundamental wave of the stator is superimposed on the excitation winding to flow an AC current, and the AC current of this excitation winding is added to the excitation current of the stator winding. Since it works, the AC current of the stator winding becomes large and the capacity of the main winding becomes large. To eliminate this drawback, a large series inductance L is required in the exciting circuit. For this reason, insert a large series reactor, or, as another method, separate the excitation winding with a different number of poles from the stator and the number of poles of this excitation winding so as not to be affected by the stator winding. Had to make up the rotor.

Since such a technique not only complicates the structure of the synchronous motor but also increases the size thereof, it cannot be employed particularly in a synchronous motor capable of starting an induction machine having a plurality of stators.

From the above, a starting torque similar to that of a general induction motor can be generated, the transition from the induction machine operation to the synchronous operation can be easily performed, the synchronous torque is large, and the brushless and easy-to-maintain synchronous motor can be used. Along with the provision, the technical problem is to provide a synchronous motor that has a small influence on the stator windings and other configurations even if the stator excitation circuit is provided in one phase of the stator.

[0011]

In order to solve the above-mentioned problems, the present applicant has two rotor cores provided on the same rotating shaft at arbitrary intervals, and the two rotor cores are provided. A rotor in which three-phase rotor windings are provided in each of the cores and connected in series, and a diode is connected in parallel to the connection point of the rotor windings, and the rotor is opposed to the two rotor cores. A stator having two stator cores that are circumferentially provided, and a main winding having a three-phase delta connection is wound around each of the two stator cores and connected to a three-phase power source; Exciting windings are provided in the same phase of the main windings of the two stator cores, and diodes are connected in series to the exciting windings so that the exciting windings are cross-connected to each other and the same as the exciting windings. the line voltage applied to the main winding phase via an on-off switch connected in parallel with cross-connect point of the exciting winding The exciter and the rotating magnetic field generated around the rotor core that one of the two stator main windings faces, and the rotation of the other stator main winding that faces the rotor core. Phase difference with the rotating magnetic field generated around the child core
A means for solving the above-mentioned problems is provided by a synchronous motor constituted by a phase shift device which causes 0 ° and a phase difference of 180 ° .

[0012]

The operation of the phase shifter provided in the induction motor having a plurality of stators is disclosed by the present applicant in Japanese Patent Laid-Open No. 1283/1986.
The details are described in JP-A-14.

The operation of the synchronous motor according to the present invention will be described. The synchronous motor has two rotor cores provided on the same rotary shaft at arbitrary intervals, and three-phase rotor windings are provided on each of the two rotor cores and connected in series. In parallel with the rotor winding connection point
A rotor connected to a rotor and two stator cores provided around the two rotor cores so as to face each other, and each of the two stator cores has a three-phase delta connection main winding. A stator having a wire wound around it and connected to a three-phase power source , and excitation windings are provided in the same phase of the two main windings, respectively, and diodes are connected in series to the excitation windings to form the excitation. An exciter in which windings are cross-connected to each other and a line voltage applied to the main winding in the same phase as that of the exciting winding is connected in parallel to the cross-connecting point of the exciting winding via an open / close switch; Rotating magnetic field generated around one rotor main winding around one of the stator main windings and another stator main winding generated around the rotor core facing it 0 ° phase difference with the rotating magnetic field
And a phase shifter for producing a phase difference of 180 ° .

According to this structure, at the time of start-up, the rotating magnetic fields of the main windings provided on the two stator cores cause
In order that the voltages induced in the rotor windings of the two rotor cores should be in phase, that is, the current circulating in the rotor windings of the two rotor cores should flow and be parallel to the connection points of the rotor windings. The phase shifter is actuated so that no current flows in the diode provided in, and the diode is started as a general induction motor.

At this time, the open / close switch of the exciter is open, and the rotating magnetic field of the stator causes a voltage to be induced in the exciting windings of the two stator cores to circulate the exciting windings. Currents try to flow, but no current flows in the exciting windings because the diodes are connected in the opposite direction due to the cross-connection of the exciting windings. Therefore, no static magnetic field is generated at startup.

After starting, the rotation speed of the rotor increases and the rotation speed of the rotating magnetic field approaches the synchronous speed. Up to this point, the operation is as an induction motor. Next is S =
When the phase shifter is activated when the value approaches 0.05, the opening and closing switch of the exciter is closed and the motor starts synchronous operation. This works as follows.

Of the two stator main windings, one of the stator main windings has a rotating magnetic field generated around the rotor core that faces it, and the other stator main winding has a rotor core that faces it. The phase shifter is operated so as to generate a phase difference of θ = 180 ° with the rotating magnetic field generated around the.

Since the voltages induced in the two rotor windings by these rotating magnetic fields have a phase difference angle of 180 °, the circulating current that has been flowing so far does not flow and is parallel to the connection point of the rotor windings. A current flows through the diode provided.

At this time, since the open / close switch of the exciter is closed, the same line voltage as one phase of the stator winding provided with the exciting winding is applied to the exciting winding. The applied line voltage is rectified by the diode of the exciting winding, and a rectifying current flows in the exciting winding to generate a static magnetic field.
Since a line voltage is applied to this exciting winding, it forms a parallel circuit with the main winding of the stator to which the same line voltage is applied. It also flows into the main winding of. So in the end,
A static magnetic field is created by the difference between the magnetic flux of the excitation winding and the magnetic flux of the main winding due to this rectified current.

In this way, a static magnetic field is generated in the excitation windings, and the static magnetic fields generated are in mutually opposite directions because the excitation windings are cross-connected, and the phase difference angle is θ = 18.
It is 0 °. A voltage is induced in the two rotor windings by this static magnetic field, and a circulating current due to this voltage does not flow, and a diode provided in parallel at the connection point of the two rotor windings is used.
The rectified current flows through the battery.

Therefore, the DC component of the rectified current flowing through the rotor winding excites the rotor to form a magnetic pole, and a synchronous torque is generated between the rotor and the rotating magnetic field of the main winding of the stator. Operate synchronously.

Conventionally, the voltage induced in the exciting winding by the rotating magnetic field of the stator winding flows through the diode of the exciting winding and is rectified to form a static magnetic field, but at the same time, there is an alternating current. On the contrary, this current causes a compensation current to flow in the stator winding. The compensating current is forced to increase the capacity of the stator side in addition to the current flowing through the stator, which causes a decrease in power factor.

According to the present invention, the line voltage of the stator main winding having the same phase as the position where the exciting winding is provided is applied to the exciting winding. The alternating current component of both the voltage induced by the magnetic field and the line voltage is added,
Eventually, a current due to the difference voltage between the line voltage and the induced voltage will flow. Since the line voltage has a high potential, the direction is opposite to the exciting current induced by the rotating magnetic field of the stator and flowing. A compensating current flows on the side of the stator due to the current due to this difference voltage, but this compensating current becomes a lead current with respect to the current flowing through the stator, and contrary to the prior art, a decrease in the current flowing through the stator and This has led to the improvement of the power factor on the primary side.

Considering the synchronous torque, the phase of the rotating magnetic field produced by one of the two stators is shifted by 180 ° from the phase of the rotating magnetic field produced by the other stator. However, due to the static magnetic field of the exciting winding, the direction of the current rectified by the diode flowing in the rotor winding of the rotor facing the one stator also flows in the other rotor winding.
Since the direction of the current rectified by the motor is in the opposite direction, the synchronous torque is the same in all rotors, and the synchronous torques are all added, so that the synchronous motor of the present invention has two fixed motors. Although it is a child, its total capacity is equivalent to that of an induction synchronous motor having a conventional brush.

A rectified direct current flows through the rotor winding due to the voltage induced in the rotor by the static magnetic field of the excitation winding,
Since the rotor winding acts as a DC field winding, it is possible to provide a synchronous motor that has a large synchronous torque and does not require maintenance such as brushes.

In this way, the induction motor is started and the transition to the synchronous motor is performed by switching by the phase shifter. This phase shifter has the phase of the rotating magnetic field produced by one of the two stators. A phase difference angle of θ = 180 ° is provided in electrical angle with respect to the phase of the rotating magnetic field generated by another stator. In the present invention, one of the two stator windings is wound. The terminals of the stator winding are switched by a switch so as to switch the polarities of the wires, and are connected to the power supply. As another method of providing the phase difference, it is also possible to provide it by rotating either one of the stators about the rotation axis, but in the case where the switching needs to be performed instantaneously as in the present invention. The switch can be switched more quickly and accurately.

By the way, the stator excitation winding may be either single-phase or three-phase.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention mainly describes an example in which two stator main windings are connected in parallel to a power source.
It may be connected in series to the power source and is not limited to this example. In the case of the rotor winding, the same applies to both star connection and delta connection.

The applicant has already described in detail in Japanese Examined Patent Publication No. 27920/1990, the construction and operation of an induction motor having a plurality of stators, which is a part of the construction of the present invention. For example, of a plurality of stators, a rotating magnetic field generated around a rotor facing a specific stator and a rotating magnetic field generated around a rotor facing another stator by a voltage phase shifter. When the phase difference between and is, for example, the same phase, that is, an electrical angle of 0 °, the current flowing through the rotor conductor returns to the rotor conductor, and, for example, when an electrical angle is 180 °,
It explains in detail that the current flowing through the rotor conductors flows through the connecting material that connects the rotor conductors between the rotor cores.

Further, regarding the constitution of the phase shifter, there are shown a constitution in which the stator is rotated and a constitution in which the connection of the stator main winding is switched, but in the present invention,
In particular, if the phase shifter is configured to switch the polarity of the stator main winding, the electrical angle can be switched from 0 ° to 180 ° instantaneously, so that the synchronous speed can be easily pulled. In addition, if a sensor for detecting the rotation speed and a control device for the phase shifter are provided to communicate with each other, the pull-in to the synchronous speed can be automated, and even if a step out occurs, the signal from the sensor for detecting the rotation speed can be used. It is possible to immediately switch from the synchronous operation to the operation of the induction motor, and unlike the general synchronous motor, there is no sudden stop from step out, and accident prevention can be easily performed.

An embodiment of the present invention will be described with reference to FIG. FIG. 1 shows only the windings of the stator and rotor of the synchronous motor of the present invention. First, reference numeral 1 indicates the stator side of the synchronous motor, and reference numeral 2 also indicates the rotor side.

First, on the stator side 1, a star-connected first main winding 3 and a second main winding 4 provided in each of two stator cores (omitted) are connected in parallel to a three-phase AC power supply 5. It is connected to the. Exciting windings 6 and 7 are provided in the same phase of the two main windings 3 and 4 on the stator side 1, and diodes D ₁ and D ₂ are connected in series to the exciting windings 6 and 7, The excitation windings 6 and 7 are cross-connected to each other. Further, the line voltage Vrs, which is the same as one phase of the main windings 3 and 4, is connected in parallel to the cross connection point of the excitation windings 6 and 7 via the open / close switch S ₁ and the exciter 10 is connected.
There is.

On the other hand, on the rotor side 2, two rotor cores (omitted) are provided with rotor windings 8 and 9, respectively, and the rotor windings 8 and 9 are connected in series, and Winding 8,
Diodes D ₃ and D ₄ are connected in parallel between the connection points of 9.

In the second main winding 4 on the stator side 1, switches 13 and 14 are provided at both ends of the windings 4R, 4S and 4T of the respective phases of the main winding 4 so as to switch the polarities of the windings. And the phase shifter 15 is configured.

Here, the excitation winding 6 facing the first main winding 3
Let E ₁ be the voltage induced in E 2, and let E ₁ ε ^{j θ be the} voltage induced in the excitation winding 7 facing the second main winding 4. In addition, the voltage induced in the rotor winding 8 facing the first main winding 3 is E
₂ and the voltage induced in the rotor winding 9 facing the second main winding 4 is E ₂ ε ^jθ . Here, θ is the phase difference angle of the voltage.

The starting of the synchronous motor of the present invention in which each winding is constructed as described above will be described. The switches 13 and 14 of the phase shifter 15 for the second main winding 4 are turned on to the A side, and the open / close switch S ₁ is opened to power the first main winding 3 and the second main winding 4 in parallel. Put in 5. In this case, the phase shifter 15
Does not work, so θ = 0.

At this time, the open / close switch S of the exciter 10
₁ is open, and the exciting magnetic fields 6 and 7 of the two stator cores are supplied with voltages E ₁ and E by the rotating magnetic field of the stator.
₁ ε ^jθ induces currents to flow so as to ^circulate in the excitation windings 6 and 7. However, these currents are generated by connecting the excitation windings 6 and 7 in a diode D ₁ , D ₂
Since they are connected in the opposite direction, they do not conduct, and no circulating current flows through the excitation windings 6 and 7 through the diodes D ₁ and D ₂ . Therefore, no static magnetic field is generated at startup.

On the other hand, the rotor windings 8 and 9 have main windings 3 and 4, respectively.
The voltages E ₂ and E ₂ ε ^jθ are induced by the rotating magnetic field, but since the phase shifter is not operating, θ = 0, so a circulating current flows and the motor is started as a general induction motor. In this case, diode - since the terminal voltage of the de _D 3, _{D 4} is zero diode - no current flows through the de _D 3, _{D 4.}

Next, a description will be given of how to bring in synchronization.
Set the switches 13 and 14 of the phase shifter 15 of the second main winding 4 to B
Then, the second main winding 4 is reversed in polarity and connected.
Further, the open / close switch S ₁ is turned on to connect the exciting windings 6 and 7 to the line voltage Vrs.

In this way, the phase difference angle θ of the rotating magnetic field of the stator main winding becomes θ = 180 °. That voltage induced to the excitation winding 6 and 7 _{^E 1, E} 1 _{ε j180} ^° becomes _{E 1} epsilon
^{Although j180 °} = −E ₁ , the exciting windings 6 and 7 are cross-connected, so that currents in opposite directions cancel each other out.

At this time, the open / close switch S _{1 of the} exciter 10
Is closed, the line voltage Vrs, which is the same as one phase (3R, 4R) of the stator winding provided with the excitation windings 6 and 7, is applied to each of the excitation windings 6 and 7. The applied line voltage Vrs is rectified by the diodes D ₁ and D ₂ of the excitation windings 6 and 7, and a rectified current flows in the excitation windings 6 and 7 to generate a static magnetic field. Here, as shown in FIG.
Since the line voltage Vrs is applied to the excitation windings 6 and 7, the main winding 3R of the stator to which the same line voltage is applied,
It is a parallel circuit with 4R, and the excitation winding diode D
_{1. A} part of the rectified current by D ₂ is the main winding 3 of the same phase.
It will also flow to R and 4R. Therefore, finally, a static magnetic field is created by the difference between the magnetic fluxes of the excitation windings 6 and 7 and the magnetic fluxes of the main windings 3R and 4R due to the rectified current.

In this way, a static magnetic field is generated in the exciting windings, and the static magnetic fields generated are in opposite directions because the exciting windings are cross-connected, and the phase difference angle is θ = 18.
It is 0 °.

Now, at the synchronous speed, the induced voltages E ₂ , E ₂ ε of the rotor windings 8, 9 due to the rotating magnetic fields of the main windings 3, 4 are generated.
Both ^jθ are zero, but the static magnetic field induces the voltages E ₂ , E ₂ ε ^jθ in the rotor windings 8 and 9. In this case, θ = 180 °, so E2ε ^j 180 ^° = −E ₂ . As a result, no circulating current flows through the rotor windings 8 and 9, and
The current rectified through the terminals D ₃ and D ₄ is applied to the rotor winding 8,
9, the rotor windings 8 and 9 are excited by a direct current component to form magnetic poles, and torque is generated between the rotor windings 8 and 9 and the rotating magnetic fields of the main windings 3 and 4 to reach synchronous operation.

With the above construction, the synchronous motor according to the present invention is started with a torque characteristic similar to that of the conventional induction motor with the phase difference angle θ = 0 ° at the time of start, and the slip S becomes, for example, S = 0.05. At this time, the switch of the phase shifter is switched to set the phase difference angle to θ = 180 °, the synchronous speed is shifted to operate with the torque characteristic of the synchronous motor. With such a configuration, the synchronous motor of the present invention does not require a starter, a DC power source, or a brush, so that not only the structure and the configuration thereof are simplified, but also the conventional induction motor can be started with the same torque characteristics. Therefore, even if the heavy load is applied, it is possible to shift from the startup to the synchronization simply by switching the switch of the phase shifter.

Conventionally, the voltage induced in the exciting windings 6 and 7 by the rotating magnetic fields of the stator windings 3 and 4 flows through the diodes D ₁ and D ₂ of the exciting windings 6 and 7 as described above. ,
The static magnetic field is rectified to generate a static magnetic field, but at the same time, an alternating current also exists, and this current causes a compensating current to flow in the stator windings 3 and 4 on the contrary. The compensating current is forced to increase the capacity of the stator side in addition to the current flowing through the stator, which causes a decrease in power factor.

According to the present invention, the line voltage Vr of the stator main windings 3R and 4R in the same phase as the position where the excitation windings 6 and 7 are provided.
Since s is applied to the excitation windings 6 and 7, the voltage E induced by the rotating magnetic field of the stator is applied to the excitation windings 6 and 7.
The AC component of both ₁ and the line voltage Vrs is added, and finally, the AC component current due to the difference voltage obtained by subtracting the induced voltage E ₁ from the line voltage Vrs comes to flow. A compensating current flows on the side of the stator due to the AC component current due to this difference voltage, but this compensating current becomes a lead current with respect to the current flowing through the stator, and contrary to the prior art, the current flowing through the stator decreases and is fixed. This led to the improvement of the power factor of the child (primary side).

By constructing the diodes D ₁ and D ₂ by thyristors, it is possible to control the exciting current of the exciting winding. In this case, the exciting current is controlled to control the stator main winding. The static magnetic field can be controlled together with the control of the rectified current flowing through the static magnetic field. With the above configuration, the synchronous motor according to the present invention has a phase shift angle of θ = 0 at start-up.
When the slip S becomes, for example, S = 0.05, the switch of the phase shifter is switched to set the phase shift angle to θ = 180 ° and the synchronous speed to the synchronous speed. It shifts and operates with the torque characteristics of the synchronous motor. With such a configuration, the synchronous motor of the present invention does not require a starter, a DC power source, or a brush, so that not only the structure and the configuration thereof are simplified, but also the conventional induction motor can be started with the same torque characteristics. Therefore, even if the heavy load is applied, it is possible to shift from the startup to the synchronization simply by switching the switch of the phase shifter.

[0048]

As described above, the synchronous motor of the present invention has the following structure.
Performs startup with the same torque characteristics as conventional induction motors,
For example, the speed of the rotor shifts from the vicinity of slip S = 0.05 to the synchronous speed and the rotor is operated with the torque characteristics of the synchronous motor. Since this synchronous motor does not require a starter, DC power supply, or brush, it not only has a simple structure and configuration, but it can be started with the same torque characteristics as conventional induction motors, so even if a heavy load is applied. It is possible to shift from startup to synchronization.

Further, according to the present invention, the influence of the compensating current of the stator main winding, which is induced by the current flowing in the exciting winding, may be made to be a compensating current that is advanced with respect to the motor main winding, contrary to the conventional case. Since it has been completed, it can greatly contribute to the improvement of the motor power factor.

By the way, since the synchronous motor of the present invention has the torque characteristics of both the induction motor and the synchronous motor,
The torque characteristics of either motor can be used. This means that even if a step out occurs for some reason during operation at synchronous speed, it is possible to operate by switching from the torque characteristics of the synchronous motor to the torque characteristics of the induction motor. Never stop.

As described above, since there is no brush and a complicated structure is not required, it is possible to provide a synchronous motor that is easy to maintain and has high reliability and has a large starting torque.

[Brief description of drawings]

FIG. 1 is a diagram showing only a winding portion of a stator and a rotor of an embodiment of a synchronous motor according to the present invention.

FIG. 2 is a diagram showing another embodiment of the excitation winding according to the embodiment of the present invention.

[Explanation of symbols]

1 Stator side 2 rotor side 3 First main winding 4 Second main winding 5 Three-phase AC power supply 6 excitation winding 7 excitation winding 8 rotor winding 9 rotor winding 10 exciter 13 switch 14 switch 15 Phase shifter D1 diode D2 diode D3 diode D4 diode S1 open / close switch

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02K 19 / 00,17 / 00

Claims (3)

(57) [Claims] 1. A rotor having two rotor cores provided at arbitrary intervals on the same rotary shaft, each of the two rotor cores being provided with a three-phase rotor winding, and each rotor core being connected in series. A rotor having a diode connected in parallel to a connection point of the rotor winding, and two stator cores provided around the two rotor cores so as to face each other. a stator connected to the three-phase power supply by winding a primary winding that is a three-phase delta connection in each of the two stator core, each excitation winding in the same phase of the two main winding provided A diode is connected in series to the excitation winding so that the excitation winding is cross-connected to each other and is excited.
An exciter in which a line voltage applied to the main winding of the same phase as the magnetic winding is connected in parallel to the cross connection point of the excitation windings via an open / close switch, and the two stator main windings position between the rotating magnetic field one of the rotating magnetic field generated around the rotor core stator main winding facing to the other stator main winding of the results around the rotor core which faces thereto Phase difference 0 ° and phase
A synchronous motor comprising a phase shift device for producing a difference of 180 ° . 2. The phase shifter synchronizes at startup with a phase difference of 0 °.
The phase difference when pulling in is 180 ° and the opening and closing switch
The switch must be opened at startup and closed at the time of synchronization.
The synchronous motor according to claim 1, wherein: 3. The phase shifter is either one of the two stators.
Switch the polarity of the stator winding with a switch and connect to the power supply
The synchronous power supply according to claim 1, characterized in that
Motive.