JPH09135570A - Multiple rectifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a large harmonic suppression effect with a small transformer capacity, a small size and a low cost. SOLUTION: A multiple rectifier is composed of first and second three-phase full-wave rectifiers to which first and second three-phase AC voltages having 30 degrees phase difference between each other and having identical amplitudes are inputted through their respective three-phase AC input terminals and which output rectified DC voltages and which are connected in parallel to each other on the output side. In this case, a three phase transformer which has a star-delta winding connection or a delta-star winding connection and whose voltage ratio of the primary winding to the secondary winding is 1:1 is provided. The AC input terminals of the first three-phase full-wave rectifier 5 are connected to a three-phase AC power supply, the primary winding of the three-phase transformer is connected to the three phase AC power supply and the output terminals of the secondary windings of the three-phase transformer are connected to the three-phase AC input terminals of the second three-phase full-wave rectifier 6. The phase discrepancy between the AC inputs of the first and second three-phase full-wave rectifiers 5 and 6 which is caused by the leakage inductance of the three-phase transformer is compensated by a three-phase reactor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier circuit for converting a three-phase AC voltage into a direct current by a control type or non-control type rectifier, and in particular, a multiple rectification for reducing voltage / current ripple by connecting multiple rectifier circuits. Regarding the circuit.

[0002]

2. Description of the Related Art In a controlled rectifier circuit using a thyristor, the output voltage ripple changes depending on the control phase angle.
The maximum is obtained when the control angle is 90 °. At this time, the ripple current also increases at the same time. Even in a non-controlled rectifier circuit using a diode, in the capacitor input type having a smoothing capacitor, a steep current starts to flow when the line voltage of the power supply exceeds the capacitor voltage, so that the ripple current is large.

Generally, when the ripple current is large, the harmonic component of the power supply current becomes large, and the loss in the power distribution network increases. In addition, this harmonic component distorts the waveform of the power supply voltage and adversely affects other devices. Such inconvenience caused by the harmonic components of the power supply current is improved by inserting the reactor on the AC side or the DC side of the rectifier circuit, but it is necessary to increase the inductance of the reactor to obtain a sufficient effect. . But,
Increasing the inductance of the reactor increases the size and cost of the reactor and causes a voltage drop due to the inductance.

This harmonic problem occurs regardless of whether the number of alternating current phases is single phase or three phase. In particular, in the case of rectifying three-phase alternating current, as a solution to the above problem,
Conventionally 3 with a single primary winding in delta or star connection and two secondary windings in star and delta connection
A multiple rectifier circuit including a phase transformer and two three-phase full-wave rectifier circuits is used.

FIG. 3 is a block diagram of a conventional multiple rectifying circuit. The three-phase AC power supply 1 is connected to the delta connection terminal of the primary winding of the transformer 2, and the delta connection terminal of the secondary winding is connected to the AC side terminal of the three-phase full-wave rectifier circuit 5. The star connection terminal of the secondary winding of the transformer 2 is 3
It is connected to the AC side terminal of the phase full-wave rectifier circuit 6. In this way, the corresponding phases of the three-phase AC input voltages of the three-phase full-wave rectifier circuits 5 and 6 have a phase difference of 30 degrees from each other. The DC sides of the three-phase full-wave rectifier circuits 5 and 6 are connected in parallel to supply DC power to the load machine. In this device, the winding ratio of the two secondary windings to the primary winding of the transformer 2 is set to be the same voltage ratio. The circuit configurations of the three-phase full-wave rectifier circuits 5 and 6 are the same. Therefore, the rectifying characteristics of the two rectifying circuits are the same. As a result, the DC outputs of the three-phase full-wave rectifier circuits 5 and 6 each have a frequency that is 6 times the frequency f of the AC power supply, have the same amplitude as each other, and are 30 degrees apart from each other (of the AC power supply). It includes a voltage ripple having a phase difference of one cycle (360 degrees). Therefore, when the outputs of the three-phase full-wave rectifier circuits 5 and 6 are superposed, the ripples of the DC output voltages of the rectifier circuits 5 and 6 overlap each other in opposite phases and cancel each other out, resulting in a voltage ripple of a frequency of 12f and a small amplitude. Become.

FIG. 4 is a circuit diagram of an example in which the multiple rectifier circuit of FIG. 3 is applied to a capacitor input type rectifier circuit. 3
Each phase terminal of the phase alternating current power supply 1 is connected to the delta connection terminal of the primary winding of the transformer 2, and the delta connection terminal of the secondary winding is 3
It is connected to each phase AC input terminal of the phase full wave rectifier circuit 5. The star connection terminal of the secondary winding of the transformer 2 is connected to each phase AC input terminal of the three-phase full-wave rectifier circuit 6. In the example of FIG. 4, the three-phase full-wave rectifier circuits 5 and 6 are uncontrolled diode bridge circuits. Three-phase full-wave rectifier circuit 5, 6
The DC output side of is connected in parallel and is connected to the load machine.
The smoothing circuit is a capacitor input type, and the smoothing capacitor 8 smoothes the output voltage of the multiple rectifier circuit.

The three-phase full-wave rectifier circuits 5 and 6 may be either a controlled three-phase bridge circuit using a thyristor or an uncontrolled three-phase bridge circuit using a diode, but in the case of a thyristor system, a voltage ripple on the DC side. An interphase reactor may be inserted in the DC circuit in order to suppress the circulating current caused by the phase difference of. In this case, the rectified voltage is supplied to the load machine from the midpoint of the interphase reactor.

An invention in which the multiple rectifier circuit shown in FIGS. 3 and 4 is further improved is disclosed in, for example, Japanese Patent Laid-Open No. 58-1703.
No. 70 is disclosed. The multiple rectifier circuit described in this publication is basically a control type multiple rectifier circuit having the same structure as the multiple rectifier circuits shown in FIGS. 3 and 4, but with a secondary winding in the interphase reactor. To form a single-phase transformer, full-wave rectify the induced voltage induced in this winding by the current ripple of the current flowing in the interphase reactor, and the resulting voltage is connected in series with the output voltage of the interphase reactor. The voltage obtained by superimposing is applied to the load. As a result, the frequency of the voltage ripple is 24 times the frequency of the AC power supply, which is equivalent to the case of rectifying 24-phase AC. By this method, the ripple of the DC output voltage can be significantly reduced, and the harmonic component of the power supply current can also be reduced. Further, in the case of the capacitor input type rectifier circuit, the ripple of the capacitor current is reduced, so that the capacitor can be downsized.

[0009]

In the conventional multiplex rectifier circuit described above, it is necessary to prepare a transformer having two types of secondary windings of delta connection and star connection, as described above. In addition, since the transformer is required to have a transformer capacity corresponding to the full load of the load machine, not only the cost increases but also the size increases.

An object of the present invention is to provide a multiple rectifier circuit which has a small transformer capacity, a low cost, and a small size without losing the advantages of the conventional multiple rectifier circuit capable of reducing the voltage ripple. It is in.

[0011]

In order to solve the above problems, the multiple rectification circuit of the present invention comprises a primary winding of a first connection and a secondary winding of a second connection, and a voltage ratio Has a 1: 1 three-phase transformer, the three-phase AC input terminal of the first three-phase full-wave rectifier circuit is connected to a three-phase AC power supply, and the three-phase AC input of the primary winding of the three-phase transformer The terminal is connected to the 3-phase AC power supply, and the 3-phase AC output terminal of the secondary winding of the 3-phase transformer is connected to the 3-phase AC input terminal of the second 3-phase full-wave rectifier circuit. Here, one of the delta connection and the star connection of the three-phase transformer is the first connection, and the other is the second connection. As described above, in the present invention, the primary winding and the secondary winding are star-delta connected or delta star connected, so that only one secondary winding is used for the first and second three-phase windings. The three-phase AC input of the full-wave rectifier circuit is provided with a phase shift of 30 degrees, whereby the voltage ripples of the rectified outputs of the first and second three-phase full-wave rectifier circuits can be superimposed in opposite phases.

In order to suppress the voltage ripple contained in the DC output by superimposing the two voltage ripples in opposite phases, the AC inputs of the first and second three-phase full-wave rectifier circuits have the same amplitude, and , The phases need to be shifted from each other by 30 degrees. In the former, the primary winding and 2
This is achieved by defining the number of turns of the secondary winding. The latter is by providing a compensating means for compensating for a relative phase shift between the three-phase AC inputs of the first and second three-phase full-wave rectification circuits caused by the leakage inductance of the three-phase transformer. To be achieved.

As a compensating means, a three-phase reactor having an inductance of the same magnitude as the leakage inductance of the three-phase transformer is provided between the three-phase AC power supply and the three-phase AC input terminal of the first three-phase full-wave rectifier circuit. It is appropriate to connect.

In this way, the same harmonic reduction effect as in the conventional method can be obtained with a three-phase transformer having a capacity about half that of the conventional method. The above three-phase reactor is equivalent to the leakage inductance of the three-phase transformer, so it is smaller than the three-phase transformer.

[0015]

FIG. 1 is a block diagram showing an embodiment of the present invention. In the following description, the frequency of the three-phase AC power supply voltage is f.

The multiple rectifier circuit of the present invention is a three-phase transformer 3
(Hereinafter referred to as a transformer 3), a reactor 4, and three-phase full-wave rectification circuits 5 and 6 are provided. The transformer 3 is a delta star connection and the primary winding delta connection terminal is a three-phase AC power supply 1
The star connection terminal of the secondary winding of the transformer 3 is connected to the three-phase AC input terminal (hereinafter, referred to as an AC input terminal) of the three-phase full-wave rectifier circuit 6. Further, in the transformer 3, the winding ratio of the primary winding and the secondary winding is set so that the voltage ratio becomes 1: 1. As a result, if the leakage flux of the transformer 3 is very small, the AC input voltage of the three-phase full-wave rectifier circuit 6 and the output voltage of the three-phase AC power supply 1 have a phase difference of 30 degrees from each other, and , Will have the same amplitude. Therefore, in this case, simply connecting the output terminal of the three-phase AC power supply 1 directly to the AC input terminal of the three-phase full-wave rectification circuit 5 and the AC input of the three-phase full-wave rectification circuit 5 and the three-phase full-wave rectification The AC input of the circuit 6 has the same amplitude, and
It is possible to have a phase difference of 30 degrees from each other.
Hereinafter, the AC input of the three-phase full-wave rectifier circuit 5 and the AC input of the three-phase full-wave rectifier circuit 6 have the same amplitude, and are mutually 3
The condition of having a phase difference of 0 degree is referred to as an amplitude / phase condition. Further, the AC inputs of the three-phase full-wave rectifier circuits 5 and 6 will be referred to as first and second AC inputs, respectively.

However, in practice, the transformer 3 has a leakage inductance, and therefore, by directly connecting the output voltage of the three-phase AC power source 1 to the AC input terminal of the three-phase full-wave rectifier circuit 5, the first and second transformers are connected. AC input cannot meet the amplitude and phase conditions. For that purpose, a three-phase reactor 4 (hereinafter, referred to as a reactor 4) having substantially the same inductance as the leakage inductance of the transformer 3 is connected to the three-phase AC power sources 1 and 3.
It is connected between the phase full-wave rectification circuit 5 and by this, the deviation from the amplitude / phase condition of the first and second AC inputs due to the leakage inductance of the transformer 3 is compensated. In this way, the three-phase AC voltages applied to the AC input terminal of the three-phase full-wave rectifier circuit 5 and the AC input terminal of the three-phase full-wave rectifier circuit 6 have a phase difference of 30 degrees with each other and are the same. Has amplitude.

Three-phase full-wave rectifier circuit 5 and three-phase full-wave rectifier circuit 6
And have the same circuit configuration. Therefore, as long as the first and second AC inputs satisfy the amplitude / phase conditions, the voltage ripple of the rectified output of the three-phase full-wave rectifier circuit 5 and the voltage ripple of the rectified output of the three-phase full-wave rectifier circuit 6 are Converted to the phase angle of the three-phase AC power supply voltage, they have a phase difference of 30 degrees. That is, both the rectified output of the three-phase full-wave rectifier circuit 5 and the rectified output of the three-phase full-wave rectifier circuit 6 are direct currents having a frequency 6f and mutually opposite phases and voltage ripples of the same amplitude. Therefore, when these two rectified outputs are connected in parallel and superposed, voltage ripples of the same amplitude and opposite phase cancel each other out to form a DC voltage having a small amplitude and a voltage ripple of frequency 12f. In this way, DC power with a small ripple amplitude is supplied to the load machine 7.

In the above embodiment, the inductance of the three-phase reactor 4 is set to be approximately the same as the leakage inductance of the transformer 3. Therefore, the smaller the leakage inductance of the transformer 3 is, the smaller the reactor 4 is, which is suitable for the purpose of the present invention. However, in reality, when the leakage inductance is small, the internal impedance of the transformer becomes small, so that there is a danger when an unexpected situation such as a short circuit occurs in the load. Therefore, in order to achieve the object of the present invention, it is advantageous that the leakage inductance is small,
The transformer 3 is designed to have an appropriate leakage inductance in consideration of the fact that the leakage inductance cannot be made too small. In any case, since the leakage inductance of the transformer is about several percent of the total inductance, the reactor 4 of the present invention is smaller than the secondary winding of the delta connection of the transformer 2 shown in FIGS. Of course.

In the multiple rectification circuit of FIG. 1, the transformer 3 of delta star connection is used, but a transformer of star delta connection may be used. Which one is selected is determined depending on whether the neutral point grounding is taken on the primary side or the secondary side of the transformer 3.

FIG. 2 is a circuit diagram of an example in which the circuit of FIG. 1 is applied to a capacitor input type rectifier circuit.

The R, S, and T phase terminals of the three-phase AC power supply 1 are 3
It is connected to the input terminal of the phase reactor 4 and the delta connection terminal of the primary winding of the transformer 3. The output terminal of the three-phase reactor 4 and the star connection terminal of the secondary winding of the transformer 3 are connected to the R, S, and T branches of the three-phase full-wave rectifier circuits 5 and 6, respectively. The three-phase full-wave rectifier circuits 5 and 6 are uncontrolled rectifier circuits having the same circuit configuration using diodes. The rectified outputs of the two rectifier circuits are connected in parallel, smoothed by the smoothing capacitor 8, and then supplied to the load machine.

The multiple rectifier circuit of FIG. 2 is a capacitor input type in which the DC sides of the three-phase full-wave rectifier circuits 5 and 6 are connected in parallel and smoothed by the capacitor 8. When the smoothing circuit is of the capacitor input type, a steep current for charging the capacitor flows to the AC side of the three-phase full-wave rectification circuits 5 and 6, but the voltage of the star connection and the delta connection of the transformer 3 is 30%.
The steep currents that charge the capacitor cancel each other out due to the phase difference in degrees, so that the harmonics of the current flowing in the primary winding of the transformer are greatly reduced.

In the embodiment of FIG. 2, an uncontrolled rectifier circuit is used as the three-phase full-wave rectifier circuit. However, when the rectified output power needs to be variable, a thyristor is used. A phase bridge circuit is adopted. In the case of the thyristor type, the voltage ripple becomes maximum when the control phase angle of the thyristor is 90 degrees. In such a case, as described above, the interphase reactor may be inserted in the DC side circuits of the three-phase full-wave rectifier circuits 5 and 6.

[0025]

As described above, the present invention has the following effects. 1) Primary winding of the first connection and 2 of the second connection
The secondary voltage of the three-phase transformer consisting of the secondary winding and having a voltage ratio of 1: 1 is connected to the second three-phase full-wave rectifier circuit, and the three-phase AC power supply voltage and the secondary voltage generated by the leakage inductance of the three-phase transformer are connected. After compensating for the change in the phase difference with the voltage by the compensating means, the three-phase AC power supply voltage is connected to the first three-phase full-wave rectifier circuit to maintain the same harmonic reduction effect as the conventional method. However, the capacity of the three-phase transformer can be halved, and the cost and size can be reduced. 2) Especially,
By connecting a three-phase reactor having an inductance substantially equal to the leakage inductance of the three-phase transformer as a compensating means between the three-phase AC power supply and the first three-phase full-wave rectification circuit, the three-phase transformer has a much smaller size than the three-phase transformer. You can make the necessary compensation with a small reactor.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of an example in which the present invention is applied to a capacitor input type rectifier circuit.

FIG. 3 is a block diagram showing a conventional multiple rectifier circuit.

FIG. 4 is a circuit diagram of an example in which the conventional method of FIG. 3 is applied to a capacitor input type rectifier circuit.

[Explanation of symbols]

 1 3-phase AC power supply 2, 3 3-phase transformer 4 Reactor 5, 6 3-phase full-wave rectifier circuit 7 Load machine 8 Smoothing capacitor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mitsuhiko Yoshiya 2-1, Kurosaki Shiroishi, Yawatanishi-ku, Kitakyushu, Fukuoka Prefecture Yasukawa Electric Co., Ltd.

Claims (3)

[Claims] 1. A first three-phase AC voltage having a phase difference of 30 degrees from each other and having the same amplitude is input to a three-phase AC input terminal to output a rectified DC voltage. A multiple rectification circuit having a second three-phase full-wave rectification circuit, wherein the first and second three-phase full-wave rectification circuits have the same circuit configuration and are connected in parallel on the output side. In 3
When one of the delta connection and the star connection of the phase transformer is the first connection and the other is the second connection, it consists of the primary winding of the first connection and the secondary winding of the second connection,
It has a three-phase transformer with a voltage ratio of 1: 1, the three-phase AC input terminal of the first three-phase full-wave rectifier circuit is connected to a three-phase AC power supply, and the primary winding of the three-phase transformer is the three-phase transformer. A multiple rectifier circuit, wherein the multiple rectifier circuit is connected to a three-phase AC power source, and the secondary winding of the three-phase transformer is connected to a three-phase AC input terminal of a second three-phase full-wave rectifier circuit. 2. The first and second three-phase full-wave rectifier circuits, which are generated due to the leakage inductance of the three-phase transformer,
The multiple rectifier circuit according to claim 1, further comprising compensating means for compensating a relative phase shift between the phase alternating current inputs. 3. The compensating means is connected between the three-phase AC power supply and the three-phase AC input terminal of the first three-phase full-wave rectifier circuit, and has an inductance substantially equal to the leakage inductance. The multiple rectifier circuit according to claim 2, wherein the multiple rectifier circuit includes a phase reactor.