JPS5847833Y2 - power converter - Google Patents

Description

[Detailed Description of the Invention] This invention relates to suppression of inrush current and detection of overload current in a power conversion device.

Conventionally, a single-phase inverter shown in FIG. 1 is a typical example of this type of device.

That is, when the power switch 2 is closed, the AC power from the commercial power source 1 is rectified into a forward converter 3 (in this case, it is also called a rectifying bridge because it is rectified into a single-phase full-wave waveform).

) and is converted into direct current by the bend.

The converted DC power is supplied to a DC smoothing capacitor 7 via a resistor 6, so that said capacitor 7 is gradually charged with transient phenomena.

On the other hand, at the same time as the switch 2 is closed, the timer 4 starts operating, and its time limit contact 4a closes after a while.

Then, the electromagnetic contactor 5 is excited and its make contact 5a is closed, so that the resistor 6 is short-circuited.

This series of operations is intended to suppress the charging current flowing into the capacitor 7 when the switch 2 is closed, that is, the inrush current seen from the power supply example.

The DC power thus obtained is supplied to the load 19 via the accelerator 8 and the inverter circuit 10.

This inverter circuit 10 has four transistors 11 to 1.
4 and four diodes 15 to 18, and converts the DC power into square wave AC power while intermittently controlling the power according to control commands from a switching controller 20.

Now, to briefly explain the operating principle of the inverter circuit, the four transistors 11 and 12 are paired with each other, and the remaining transistors 13 and 14 are paired and constantly activate (switch). It is something.

That is, when the switching controller acts to operate the former pair, the current flowing through the load 19 is
and in the latter pair, in the direction of arrow B.

This is equivalent to applying an alternating voltage across the load 19.

Note that the four diodes 15 to 18 are connected to the load 19.
This is particularly useful when applying inductive loads to

In this way, if a line short circuit occurs in the load 19 receiving AC power, for example, an extremely excessive current will flow through the axle 8 toward the inverter circuit 10 .

Then, the current rise rate per unit time (so-called di/dt) is suppressed and relaxed depending on the attributes of the reactor 8, so that the current rises slowly over time.

The change in current during this period is detected by the transformer 21, and the operation of the switch blower 1゜IJ controller 20 is immediately stopped. In this case, not only the load 19 but also the inverter circuit can be protected from short-circuit accidents.

In preparation for such an emergency, the four diodes 1
1 to 14 are all controlled to be non-conductive at the same time, so the load current that had previously passed through the reactor 8 is abruptly cut off, and a reverse voltage is induced across the reactor 80. .

Therefore, a diode 9 is inserted in parallel to the reactor 8 in order to absorb this reverse voltage and prevent the reactor 8 from self-whitening and dielectric breakdown.

In contrast to the conventional power converter device configured and operated as described above, this invention allows both the aforementioned inrush current control and overload current detection to be configured with a small number of parts, and at the same level as the conventional power converter. Alternatively, the present invention provides a power conversion device that can be expected to have further effects.

Hereinafter, one embodiment of this invention will be explained with reference to FIG. 2. In the figure, 1 is a commercial power source, 2 is a power switch,
3 is a forward converter, 7 is a DC smoothing capacitor, 8 is a reactor circuit, 10 is an inverter circuit, 19 is a load, 20 is a switching controller, and 21 is a current transformer. It is exactly the same as the one shown in the figure, has the same function as the inner opening, and fulfills the same role.

As is clear from the figure, in Fig. 2, the D timer 4, magnetic contactor 5, and resistor 6 shown in Fig. 1 have been deleted.
On the other hand, instead of the diode shown in FIG. 1, two diodes 22 and 23 are interconnected with their cathodes facing toward the anode side of the forward converter 3 to form a series connection, and this connection are connected in parallel to the reactor 8.

When the switch 2 is turned on in the power conversion device configured in this manner, the DC power obtained by the forward converter 3 passes through the reactor 8 or 3 and the diode 23 in the same manner as described above. I'L is supplied to the DC smoothing capacitor 7 connected to the connection midpoint of the series connection body.

In this process, the capacitor 7 is gradually charged according to the interaction between the reactors and the transient phenomenon. The voltage across the voltage increases and becomes equal to the maximum value of the commercial power source 1 minus the forward voltage drops of the forward converter 3 and the diode 23, respectively.

Then, the transient energy stored in the reactor 8 up to this point attempts to move to the capacitor 7 via the diode 23.

Then, the voltage across the capacitor 7 tends to rise further, but at this time, the diode 22 independently conducts in the forward direction, so the energy is transferred to the reactor 8, the diode 23, and the diode 22. move in order,
It is self-consumed and disappears naturally within a closed circuit consisting of these three parties.

In view of the above, according to this invention, the commercial power supply 1
The current flowing into the capacitor 7 from the side, that is, the rush current, is suppressed and relaxed, and at the same time, the voltage across the capacitor 7 is also limited to a certain voltage or less.

On the other hand, if a short-circuit accident occurs in the load 19 after the switch 2 is closed, an extremely excessive current will flow through the reactor 8 toward the inverter circuit 10.

Hereinafter, the converter 21 is
Since it can be reliably detected, there is excessive current or earth or disconnection.

In this case, a reverse voltage is applied to both ends of the reactor 8 in the same manner as described above, but it is absorbed by the series connection body consisting of the diodes 22 and 23 and disappears naturally.

In this way, according to this invention, by combining two diodes with a reactor and further combining a capacitor with this combination, the original current suppressing effect of the reactor can be made effective, and the original purpose can be achieved. can be achieved.

Another embodiment of this invention is an inverter circuit 1 shown in FIG.
0 is applied to a chopper circuit.

In this case, the components other than the chopper circuit, including the basic components of this invention, will not change in particular.
The second embodiment does not require much explanation.

[Brief explanation of the drawing]

FIG. 1 shows a typical conventional power converter including an inverter circuit. Figure 2 shows a power converter that implements this idea in light of Figure 1. 1...Commercial power supply, 2...Power switch, 3...Forward converter, 7...DC smoothing capacitor, 8...Reactor , 10...
・Inverter circuit, 19...Load, 20...
... switching controller, 21 ... current transformer,
22, 23... Diode.

Claims (1)

[Scope of utility model registration request] A power conversion device such as a chopper device that converts direct current obtained by rectifying alternating current into direct current power while controlling the power intermittently, or an inverter device that similarly converts into alternating current power, the anode side of the direct current being On the condition that a reactor is inserted in series, a series connection body formed by two diodes is connected in parallel to the reactor, and the two diodes are interconnected so that the cathodes thereof each face the anode side of the direct current. A power conversion device characterized in that a DC smoothing capacitor is connected and interposed between the connection midpoint of the series connection body and the cathode side of the DC.