JPS5821504B2 - Tanmakihen Atsukigenrino Setsuzoku Niyoru 12 Sousei Riyu Cairo - Google Patents

Description

[Detailed Description of the Invention] When obtaining DC current from a three-phase AC power supply via a rectifier,
The current on the alternating current generally includes a fifth harmonic current of about 20% and a seventh harmonic current of about 14%.

If the installed capacity is large, this harmonic current will have a harmful effect on the power supply system that cannot be ignored.

Therefore, by appropriately combining the windings of the rectifier transformer, two sets of electrically independent three-phase AC power supplies with a phase angle of 30° are obtained, and two sets of three-phase bridge rectifier circuits are connected to these. connection,
A method has been adopted in which a 12-pulse rectifier circuit is constructed in which these two sets of rectifier circuits are used in series or in parallel, and thereby the fifth and seventh harmonic components are removed from the AC power supply current.

In place of the two sets of electrically independent three-phase AC power supplies described above, this invention uses two sets of three-phase AC power supplies which are not electrically independent but whose phase angles are shifted by 30 degrees by connecting them based on the autotransformer principle. By obtaining a power supply and connecting two sets of three-phase bridge rectifier circuits in parallel to the power supply, lower harmonic currents of the AC power supply current are removed in the same manner as described above.

Although this circuit has the disadvantage that the DC system and the AC system are not electrically isolated and that the DC voltage cannot be arbitrarily selected, it has the advantage that the transformer capacity can be significantly reduced.

Furthermore, if this circuit is used as an inverse converter and combined with a synchronous motor, a so-called non-commutator motor that does not contain the fifth and seventh harmonic components in the phase current can be constructed.

Next, the present invention will be specifically explained based on the most efficient embodiment shown in the drawings.

In FIG. 1, a primary winding IL21 of a three-phase transformer 2 connected according to the autotransformer principle is supplied with power from a three-phase AC power supply 1.
, 31 are △ connected, and the secondary windings 12, 13, 22,
The voltage at 23,32.33 is chosen to be 0.149 times that of the primary winding.

In this way, if the voltage vectors of terminals 10, 20 and 30 are represented by 10', 20', and 30' in FIG.
The voltage vector of 4°35 is 14', 15', and
24′.

25', 34', 35'.

Two sets of three-phase starting power 14' with a phase shift of 30' are thus obtained.

24', 34' and 15', 25', 35',
With the connections shown in Figure 1, two sets of three-phase bridge rectifier circuits 3,
Supply to 4.

Thyristors 16 and 1 of these two sets of three-phase bridge rectifier circuits
6', 26, 26', 36, 36' and 17, 17'
, 27, 27', 37, and 37' are fired at the same firing angle for phase control.

The inductance of the smoothing reactor 7 connected in series with the load 8 is very large, so that the load current 80 is a completely smooth DC current, and the DC currents 81 and 82 of both rectifier circuits are kept completely equal by the interphase reactors 5 and 6. and assuming that the commutation of the current between the sirisks of each bridge rectifier circuit is completed instantaneously, the current 4 in the windings 12.22 and 32 is
0,41,42 and the current in winding 13.23,33 50,5
L52 are 40', 41', and 42 in Fig. 3, respectively.
' and 50', 51'.

As shown in Fig. 52', the waveform is the same as the phase current waveform of a normal three-phase bridge rectifier circuit, and is a three-phase alternating current that conducts in a 180° section with a phase difference of 120°. The phases of the phase alternating currents are shifted by 30'.

Further, the peak value is equal to the magnitude of the DC currents 81 and 82, which is .largecircle..

As a result, the current 60 in the primary winding 11 can be calculated as follows, if the excitation current flowing through it is ignored since its magnitude is generally small.
As will be explained next, the waveform becomes smaller in size as shown at 60' in FIG.

That is, in the section indicated by A in FIG. 3, the value of the waveform 50' of the current 50 in the winding 13 is 0, and
The value of waveform 40' is +1.

Therefore, the value of the waveform 60' of the current 60 flowing through the primary winding 11 is -0,149I because the number of turns of the winding 12 is 0.149 times the number of turns of the winding 11.

In the section indicated by C in the figure, the value of waveform 50' is +1 and the value of waveform 40' is O, so the value of waveform 60' is 10, 1.
It becomes 49I.

In the section indicated by E, the value of waveform 40' changes to waveform 50' in one step.
Since the value of is 0, the value of waveform 60' is +〇, 149I
becomes.

In the section indicated by G, the value of the waveform 40' is 0 and the value of the waveform 50' is =■, so the value of the waveform 60' is -0,149I.

In the sections indicated by B and F, the values of waveforms 40' and 50' are equal, 1 and 1, and the currents of windings 12 and 13 are 40 and 5.
Since the magnetomotive force due to zero cancels out, the value of waveform 60' becomes zero.

In the section indicated by D, the values of waveforms 40' and 50' are both 0, so the value of waveform 60' is also 0.

Similarly, the current 61 in the winding 21 and the current 62 in the winding 31
The waveform of 60' is shown as 61 and 62' in FIG.
The phase is shifted by 120°.

The current 70 flowing from the terminal 10 is the current 40, 50, and 6.
Since it is the sum of 2 minus 61, the waveform 7
0' is the waveform 40', 50' and 62 as shown in FIG.
It is obtained by subtracting 61' from the sum of '.

When this 70' waveform is expanded into a Fourier series, it does not contain the fifth and seventh harmonic components.

In this case, since the two sets of three-phase power supplies are not electrically independent, two interphase reactors are always required as shown by 5 and 6.

For example, if interphase reactor 6 is omitted, thyristor 1
Circulation occurs through the six terminals 14, the winding 12, the winding 13, the terminal 15, and the cylinder 17', making it impossible to operate satisfactorily.

In this case, the interphase reactor becomes slightly larger than in a known circuit in which two sets of three-phase power supplies are electrically independent.

However, waveform 60' of FIG. As can be seen from 61' and 62', the primary winding currents of the transformer 60, 61, 6
Since the magnitude of 2 is very small, the capacitance of these windings (
If you calculate (effective value of winding voltage) x (effective value of current)), it will be very small.

Furthermore, since the number of turns and thus the voltage of the secondary windings 12, 13, etc. are small, the capacitance of these windings is also small.

In this way, the capacity of the transformer windings decreases as in a normal autotransformer, so if the transformer capacity is expressed as half of the total capacity of all the windings, the load capacity [(load 8 voltage)×(load current)] is approximately 18%.

The transformer capacity of a known circuit in which two sets of three-phase power supplies are electrically independent is approximately 103% of the load capacity.

That is, in the 12-pulse rectifier circuit of this system, the transformer capacity can be significantly reduced.

If the three-phase transformer is connected using the autotransformer principle as shown at 2' in Figure 4, it can operate in exactly the same way as in Figure 1. In comparison, not only is the connection of the three-phase transformer a little more complicated, but the transformer capacity is also a little larger.

Various other transformer connections are conceivable, but all of them have a larger capacity than the one shown in FIG.

However, it is conceivable that other connections may be suitable in order to suitably choose the DC voltage.

In Fig. 1, if the load 8 is a DC power supply and the 3-phase AC power supply 1 is a 3-phase synchronous motor, a so-called commutatorless motor circuit is constructed, and a good phase waveform like 70' in Fig. 3 is formed. It will be driven by electric current.

As described above, the rectifier circuit having the circuit configuration of the present invention can reduce lower harmonic components at a lower cost than the current of the three-phase AC power supply of the 12-pulse rectifier circuit and the motor current of the three-phase non-commutator motor circuit. Can be removed.

[Brief explanation of the drawing]

FIG. 1 shows a three-phase AC power source 1 for applying the present invention.
Two sets of three-phase bridge rectifiers supply DC power to a load 8 via two interphase reactors 5, 6 and a smoothing reactor 7 through a three-phase transformer 2 connected according to the autotransformer principle. Connections for supplying power to circuits 3 and 4 are shown. 11, 12, 13, etc. indicate the windings of the transformer, and FIG. 2 shows the phase relationship of the electromotive forces at terminals 10, 14, 15, etc. Figure 3 shows the current waveforms at each part, 40' and 5.
0' is the current waveform of windings 12 and 13, and 60' is the current waveform of winding 11.
, 70' indicates the current waveform of the terminal 10. FIG. 4 shows an example of a connection using another configuration of the transformer.

Claims (1)

[Claims] Two secondary windings having a predetermined turns ratio with respect to the primary winding in each phase of a three-phase transformer whose primary winding is connected to a 13-phase AC power supply and whose primary winding is triangularly or star-connected. Set a line. For each of the primary three-phase terminals, if the primary winding is connected in a triangular configuration, each of the two secondary windings generates a voltage with a phase lead of 90° and a voltage with a phase lag of 90° relative to the star voltage at each terminal. If the primary winding is star-shaped, connect one end of each of the two secondary windings that generate a voltage with a phase lead of 120° and a voltage with a phase lag of 120°, and connect the other end of the secondary winding with the Two sets of three-phase AC voltages with equal voltage magnitude and a phase angle of 30 degrees are generated at a total of six terminals, and these two sets of three-phase terminals are connected in parallel by providing interphase reactors at both the positive and negative poles. A 12-pulse rectifier circuit based on the autotransformer principle, characterized in that it is connected to a set of three-phase bridge rectifier circuits.