JPH06253513A - Synchronuous motor - Google Patents

Abstract

PURPOSE:To obtain a synchronous motor requiring no brush structure for DC excitation in which the stator is not affected by the AC component of DC exciting circuit. CONSTITUTION:The synchronous motor is constituted of the stator side l comprising a three-phase star-connected main winding 3 connected with a three-phase AC power supply 5 and an exciting circuit 7 where three-phase exciting windings 4 are connected in series with a diode D1, and the rotor side 2 comprising a three-phase star-connected rotor winding 6 connected in parallel with diodes D2 and D3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor having an excitation winding that does not affect the stator.

[0002]

2. Description of the Related Art In a general synchronous motor, its rotor is accelerated by a starter to a rotational speed of a rotating magnetic field formed by a stator winding, that is, near a synchronous speed, and a rotor is DC-excited by a brush from a DC power source. Is done.

However, since this brush-equipped synchronous motor requires maintenance and inspection, maintenance costs are high, and a brushless synchronous motor 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. However, 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 utilizes a harmonic magnetic field generated by the square wave voltage of the inverter by connecting a diode to the rotor winding, but the field magnetomotive force of the rotor is insufficient. However, there is a drawback that it cannot obtain high output.

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. 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.
Since the stator is inserted, the three-phase rotating magnetic field of the stator is close to the open phase state, not only smooth rotation can not be obtained, but also there is a drawback that it is not reliable in pulling into synchronous operation. It was

[0006]

In order to solve these drawbacks of the prior art, a DC excitation winding and a diode, which are induced by the rotating magnetic field of the stator, are formed in the stator in the same manner as the stator winding.
And a rotor in which a rotor winding wound around a rotor core is star-connected and a diode is connected in parallel between the lines of the rotor winding. is there.

In the direct current excitation circuit of this synchronous motor, an alternating voltage of the fundamental wave is generally induced by the rotating magnetic field of the stator winding. The AC voltage of the excitation winding induced by the fundamental wave of the stator is superimposed on the excitation winding together with the DC rectified by the diode to flow an AC current. Since it acts so as to add to the exciting current of the winding, 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 makes it large, it cannot be used in a general-purpose synchronous motor.

In view of the above, a brushless, easy-to-maintain synchronous motor having a large synchronous torque is provided, and a DC exciting circuit of the rotor is provided with windings in the same phase of the stator. Even so, the technical issue is to provide a synchronous motor that does not affect other configurations or performances.

[0010]

In order to solve the above-mentioned problems, the applicant of the present invention provides a rotor core with three-phase rotor windings to perform three-phase star connection and to connect two of the rotor windings. A rotor having a diode connected between the wires and a stator core provided around the rotor core so as to face the rotor core, and a main winding having a three-phase star connection is wound around the stator core. Windings are provided in the same phase of the stator connected to the three-phase power source and the main winding of the stator, and the total voltage induced in each winding by the rotating magnetic field of the stator does not become zero. As described above, a means for solving the above-mentioned problems is provided by a synchronous motor which is constituted by an exciting circuit which is connected in series to form an exciting coil and an exciting circuit in which terminals of the exciting coil are connected via a rectifying element.

[0011]

In the past, 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 exciting windings are connected in series via a rectifying element such as a diode. Therefore, the exciting windings have an alternating voltage and a diode induced by the rotating magnetic field of the stator. Both the current and the DC component voltage rectified by the current flow. This direct current component excites the rotor by direct current as described above, while one alternating current component acts so as to flow a compensation current to the stator side. However, since the wires are connected so that the total voltage applied to each winding of the excitation winding does not become zero, the compensating current flowing on this stator side is
In the connected stator winding, the current cannot flow so that the total current becomes zero around the neutral point of the star connection, so that the compensation current due to the excitation circuit does not occur on the stator side. is there.

Considering the synchronous torque here, a DC current rectified in the rotor winding by a voltage induced in the rotor by the static magnetic field of the excitation winding causes a flow of DC current in the rotor winding. Since it functions as a winding, it is possible to provide a synchronous motor that has a large synchronous torque and does not require maintenance such as brushes.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention mainly describes an example in which rotor windings are star-connected, but the same applies to both star connection and delta connection.

An embodiment of the present invention will be described with reference to FIG. In FIG. 1, only the stator and rotor windings of the synchronous motor of the present invention are extracted. 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 main winding 3 of a star connection provided on a stator core (not shown) is connected to a three-phase AC power supply 5. Exciting windings 4 are provided in the same phase of the main winding 3 on the stator side 1 and are connected in series via a diode D ₁ to form an exciting circuit 7.

On the other hand, on the rotor side 2, a rotor winding 6 is provided on each rotor core (omitted), the rotor winding 6 is connected to a star, and the line between the rotor windings 6 is connected. Diodes D ₂ and D ₃ are connected in parallel to the. 2 and 3, the voltage induced in the excitation winding 4 facing the main winding 3 by the voltage E ₁ of the main winding 3 is E ₂ . Further, the voltage induced in the rotor winding 6 facing the main winding 3 is e.

Since the synchronous motor of the present invention configured as described above cannot be self-started, for example, the induction motor can not be started, the inverter is used as a power source to synchronously pull in at a low frequency, and then the frequency is increased. And shift to high-speed operation.

At this time, as is apparent from FIG. 2, the rotating magnetic field of the stator (voltages E ₁ , E ₁ ε- ^{J2π / 3} , E ₁ ε).
^{J2π / 3} ) ^induces voltages E ₂ , E ₂ ε- ^{J2π / 3} , and E ₂ ε ^{J2π / 3 in} the excitation winding 4 of the stator core, respectively. At this time, when the exciting winding 4 is connected as shown in FIG. 2, the voltage V between the terminals X and Y becomes

[0020]

[Equation 1] Here, consider COS (2π / 3). As is clear from FIG.

[0021]

[Equation 2] Becomes Here, the terminal XY in which the excitation winding 4 is connected
A voltage V = 2E ₂ is generated between them. That is, during the synchronous operation, the voltage V = 2E ₂ is applied to the diode D ₁ so that the current flows through the exciting winding 4. It is considered that the current flowing through the diode D ₁ is generally a direct current component and an alternating current component, but will be described separately for the direct current component and the alternating current component.

First, FIG. 4 shows the direct current component I of the rectified current by the diode D ₁ . Next, consider the magnetic flux generated in the excitation winding 4 by this DC component I. The path for the direct current component is as shown in FIG. 4, and assuming that the magnetic flux φ is generated by this current I, first, the magnetic flux Φ produced by I of the windings a, b, c of the exciting winding 4 is a, b. , C windings are wound in three phases, and when the magnetic flux φ of the a phase is used as a reference and the magnetic flux of each phase is spatially considered as two poles, it becomes as shown in FIG. Since it is connected, the synthetic magnetic flux Φ is

[0023]

[Equation 3] (FIG. 5B).

Therefore, the magnetic flux Φ of the excitation winding formed by the DC component I is as shown in FIG. Since this magnetic flux Φ is a static magnetic field, when the rotor rotates, an electromotive force is generated in the rotor by the magnetic flux like the voltage e in FIG.

When a voltage e is induced in the rotor winding 6 by the above-mentioned static magnetic field, a rectified current flows through the rotor winding 6 through the diodes D ₂ and D ₃ and the rotor winding 6 Is excited by a direct current component to form a magnetic pole, and is attracted by the rotating magnetic field of the main winding 3 to bring the rotor to a synchronous speed.

Next, looking at the AC component of the rectified current flowing through the diode D ₁ in FIG. 4, letting this AC component be i
Flows as shown in FIG. Assuming that the alternating current i flowing through the excitation winding 4 causes the compensation current i ′ to flow through the main winding 3 in this way, at the neutral point 0, Kirchhoff's current law is

[0027]

[Equation 4] It does not hold. Therefore, the compensating current i'of the AC component i flowing in the exciting winding 4 does not flow in the main winding 3. That is, there is no interference due to the alternating current between the main winding 3 and the excitation winding 4. As a result, excitation winding 4
Has a large exciting inductance and acts so that the alternating current component i flows through the virtual exciting inductance.

Conventionally, the voltage induced in the exciting winding 4 by the rotating magnetic field of the stator winding 3 flows through the diode D ₁ of the exciting winding 4 as described above and is rectified to form a static magnetic field. At the same time, there is an alternating current, and this current, on the contrary, was supposed to flow a compensation current in the stator winding 3. Moreover, the compensating current is forced to increase the capacity of the stator side in addition to the current flowing through the stator, causing a reduction in power factor.

According to the present invention, since the exciting winding 4 is connected in series via the diode, the alternating current component of the exciting winding 4 is suppressed to a negligible influence on the stator. As a result, it has become possible to change from a synchronous motor, which previously required a large reactance, to a DC excitation circuit that does not affect the stator side.

By constructing the diode D ₁ with a thyristor, the exciting current of the exciting winding can be controlled. In this case, the static magnetic field can be controlled by controlling the exciting current. .

By the way, the synchronous motor of the present invention can be used as a generator by rotating the rotor by another drive source in this configuration.

[0032]

As described above, the synchronous motor of the present invention has the following structure.
Since it does not require a DC power supply or brush, it not only simplifies the structure and configuration, but also suppresses the influence of the compensating current of the stator main winding that is induced by the current flowing in the excitation winding. Therefore, it can greatly contribute to the improvement of the motor power factor.

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 highly reliable, and has a large synchronous 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 an induced voltage between a main winding and an excitation winding.

FIG. 3 is a vector diagram of a voltage induced in an excitation winding.

FIG. 4 is a diagram showing a current and a static magnetic flux of an excitation winding during synchronous operation.

FIG. 5 is a vector diagram showing a combination of magnetic fluxes of respective windings of an excitation winding during synchronous operation.

FIG. 6 is a diagram in which only a winding portion of a stator showing an AC component current of an exciting circuit and a compensation current of a main winding is extracted.

[Explanation of symbols]

1 Stator side 2 Rotor side 3 Main winding 4 Excitation winding 5 Three-phase AC power supply 6 Rotor winding 7 Excitation circuit D ₁ diode D ₂ diode D ₃ diode

Claims (1)

[Claims] 1. A rotor in which a rotor core is provided with a three-phase rotor winding to perform three-phase star connection, and a diode is connected between two lines of the rotor winding, and the rotor. A stator having a stator core provided around the core so as to face the core, and a main winding having a three-phase star connection wound around the stator core and connected to a three-phase power source; Each winding is provided in the same phase of the winding, and the windings are connected in series so that the total voltage induced in each winding by the rotating magnetic field of the stator does not become zero to form an exciting winding. A synchronous motor comprising: an exciting circuit in which is connected via a rectifying element.