JPS5910950Y2 - 3-phase to single-phase converter - Google Patents

Description

[Detailed description of the invention] The present invention relates to a three-phase to single-phase converter that converts three-phase AC voltage to single-phase AC voltage. This invention relates to a three-phase to single-phase converter that can take a single-phase load from a three-phase power source without balancing it.

Conventionally, as this type of three-phase to single-phase converter, a capacitor and a reactance connected to the single-phase load are provided at the load terminal, and the current flowing through the single-phase load is equally shared among each phase. It is known that an iron resonant circuit is provided on the three-phase human-powered side to keep the output voltage constant (Japanese Patent Publication No. 1570/1970).

However, since this converter controls the output voltage only in the saturation region of the reactor in the ferro-resonant circuit, it has the disadvantage that it cannot have a wide control range for input and output fluctuations, and also suffers from loss due to control. It has the disadvantage of being large.

Further, there are disadvantages in that noise is generated and the scale of the apparatus becomes large.

In view of the above points, the present invention was devised to solve such problems and eliminate such drawbacks.The purpose of this invention is to be able to cope with input/output fluctuations and to have a wide control range for input/output fluctuations. Another object of the present invention is to provide a small-scale three-phase to single-phase converter that allows easy change of the control range, has little loss, and is noiseless.

In order to achieve such an objective, the present invention provides a first linear actuator connected to the input terminal of each phase of the Sanwa circuit, and a first linear actuator connected in series between each phase of the load side of the first linear actor. A second actuator and an AC switching element connected in anti-parallel, a capacitor connected in parallel to a series circuit of the second actuator and an AC switching element connected in anti-parallel, and a single-phase load connected to a load terminal. a third transactor and a capacitor; and a pulse phase shift circuit that detects changes in the inter-phase voltage of the load terminals and controls the anti-parallel connected AC switching elements so that the inter-phase voltage becomes a constant voltage. By directly controlling each phase, the three-phase power supply is balanced and a single-phase load can be taken from the three-phase power supply.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a connection diagram showing one embodiment of the present invention, in which each phase of three phases (first phase φ1, second phase φ2, third phase φ3) is connected to input terminals (R, S, T) and Switch (Sa, Sb, Sc
) through the reactor, 7. LSa, LSb,
Connected to LSc.

Control rectifiers SCR1 and SCR2 and reactance LpU (Lpv, LpW) are connected in antiparallel between each phase on the load side of this reactance LSa - LSc.
A capacitor CpU (cpv, CpW) is further connected in parallel to the series circuit of each phase.

In this case, the control rectifying elements SCR1 and SCR2 control the current value and its phase flowing through the reactance LpU (LpV, LpW), and the inter-phase voltage V12 (■23, ■3,)
Since it is intended to control the actance LpU (LpV, Lp
Any AC switching element that turns on/off the AC to W) is fine.

On the other hand, there is a glue tank L between each phase on the load side for output stabilization.
OU and Lov are connected, a capacitor C is connected between the first phase φ1 and the second phase φ2, and a reactance L4x is connected between the second phase φ2 and the third phase φ3.

A single-phase load (
A resistive load) R is connected.

Therefore, the capacitor C and the reactance L are J-connected to the single-phase load R on the load side.

Further, each phase on the load side is manually inputted to a pulse phase shift circuit PPS.

The pulse phase shift circuit PPS detects changes in the voltage between each phase on the load side, and controls the control rectifiers SCR1 to SCR so that the voltage supplied to the single-phase load R becomes a constant voltage based on the detection result.
This is to control the conduction time (conduction angle) of No. 3.

In this case, the supply voltage to the single-phase load R is determined in advance, but the supply voltage can also be varied by adjusting the variable resistors VR1 to VR3.

Incidentally, since this pulse phase shift circuit PPS is well known, detailed explanation of its structure will be omitted.

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIGS. 2 and 3.

This FIG. 2 shows a load side connection diagram, and FIG. 3 shows a vector diagram.

First, when the switch Sa-Sc is closed, the single-phase load R is supplied with the phase-to-phase voltage V13 between the first phase φ1 and the third phase φ3. However, single-phase load R, capacitor C and reactance L
is a J-connected load as shown in Figure 2, so the phase relationship of the currents I,, I・o, and IL flowing through these single-phase load R, capacitor C, and reactance L is as follows:
The result will be as shown in the vector diagram in the figure.

That is, the current 8 is in phase with the interphase voltage V3, the current Ic is in a leading phase of T with respect to the interphase voltage 1, and the current IL is in a lagging phase of i with respect to the interphase voltage V23.

On the other hand, the currents L, L, I3 of each phase are? There is a relationship.

Therefore, after setting the currents ■R, IC, and ■L in the value relationship shown in Figure 3, and finding the phase of the currents II, I2, and I3 of each phase based on the above equation (1), these are A balanced current is obtained as shown in FIG.

That is, as long as there is no variation in input voltage or variation in unit load, the current values flowing through each phase will be equal.

However, when the input voltage changes, the current value of each phase also changes accordingly, and the balanced relationship between the phase currents collapses. However, the pulse phase shift circuit PPS detects the change in the inter-phase voltage, and changes the inter-phase voltage V2. , V23, and V31 become predetermined values, the conduction angles of the control rectifying elements SCR1 to SCR2 are controlled.

That is, for example, when the phase-to-phase voltage ■1 increases, the delay current flowing through the reactance LpU is increased by a certain amount, and the phase-to-phase voltage ■1 increases.
1 is returned to a predetermined value, and when the inter-phase voltage Vl2 drops, the delay current predetermined to flow through the reactance LpU is reduced, and the inter-phase voltage V12 is returned to the predetermined value.

Such control is similarly performed for phase-to-phase voltages V23 and V3.

As a result, the phase-to-phase voltage ■1, V 23 , V 3
is always kept at a constant voltage even if the input voltage fluctuates.

Accordingly, the currents II, I2, and I3 of each phase are also balanced.

This is because the single-phase load fluctuates, and the phase-to-phase voltages V12, V23,
Even when V3 changes, the current I of each phase is adjusted by similar control.
=, I2, I3 are maintained in equilibrium.

As is clear from the above explanation, according to the present invention, a capacitor, a reactance, and a balanced load device configured with a single-phase load are connected to the load terminals without using complicated means, and the current for the single-phase load is In addition, in response to input/output fluctuations, the load current and its phase of the reactances LSa-LSb connected to the human power side are controlled by an AC switching element.
By directly controlling the AC for each phase, a simple circuit structure that balances the three-phase power supply and takes a single-phase load from the three-phase power supply can be used to simply control the conduction angle of the AC switching element. It has the advantage of being able to deal with input/output fluctuations, widening its control range, and easily changing the control range.Furthermore, since it does not use a ferro-resonant circuit unlike conventional methods, there is no loss and there is no noise. Further, since the phase shift control portion can be housed in a printed circuit board or the like, the overall device scale can be reduced, so the practical effect is extremely large.

In the embodiment, the output voltage stabilization actances LoU, Lov, and Low are provided, but these may be added as necessary.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are load side connection diagrams and vector diagrams for explaining its operation. R, S, T... Input terminal, LSa-LSc,
LpuLpw, L-” reactance, CpU-C
pW, C... Capacitor, SCR1, SCR
2... Control rectifying element (AC switching element)
, R...Single phase load, PPS...Pulse transfer circuit.

Claims (1)

[Scope of utility model registration request] A first glue actor connected to the input terminal of each phase of the three-phase circuit, a second glue actor connected in series between each phase on the load side of the first glue actor, and an AC switching element connected in anti-parallel. , a capacitor connected in parallel to the series circuit of the second actuator and AC switching elements connected in antiparallel, and a third actuator and capacitor connected to the load terminal with a single-phase load;
and a pulse phase shift circuit that detects a change in voltage between each phase of a load terminal and controls the anti-parallel connected AC switching elements so that the voltage between each phase becomes a constant voltage, and directly controls AC for each phase. Since the three-phase power supply is not balanced by
A three-phase to single-phase conversion device characterized by being able to take a single-phase load from a phase power source.