JPH03124269A - Frequency converting device - Google Patents

Abstract

PURPOSE:To improve reliability by a method wherein a charging power source is drawn from the side of a control circuit unit, different from a main circuit power source, and is connected to the arbitrary 2-phase of a power rectifier, upon the initial charging of a large-capacity filter capacitor supplying DC power to a power inverter. CONSTITUTION:Prior to the starting of a power inverter 4, a switch 101 is thrown by a command from a control circuit unit 10 to charge a large-capacity filter capacitor 3. Successively, the finishing of the charging of the large-capacity filter capacitor 3 is confirmed by the control circuit unit 10 and, thereafter, the switch 101 is opened by a command (b), a contact 1 is thrown by a command (a) to connect a main circuit and whereby the power inverter 4 may be started. At this time point, rush current into the large-capacity filter capacitor 3 will accordingly never become a problem especially. According to this method, a highly reliable initial charging device 100 can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a large-capacity filter capacitor in a DC circuit formed by a forward converter and a self-excited inverter, and pulse width modulation of the inverter. This invention relates to a frequency conversion device that can be controlled to obtain an arbitrary voltage and frequency as an output.

[Conventional technology]

Figure 2 shows, for example, an analog control system.
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EtEcrRoNrc C (5MPC) NENTS A
ND APPL, ICATIONS) Volume 3 No. 1, 9
Monthly issue 1980. P6 to P16 Fig. 4 is a circuit configuration diagram based on the conventional self-excited frequency converter shown in Fig. 4, in which 1 is a conductor and 2 is a diode
A forward converter consisting of ~26, 201 is a current limiting resistor, 20
2 is a current-limiting resistor short-circuit switch, 3 is a large-capacity filter capacitor, and 4 is an inverter, which in this embodiment includes transistors 41 to 46 and flywheeling diodes 51 to 46.
A transistor inverter composed of 56 is used. 10 is the transistor 41 to 46 of the main circuit.
This is a control circuit section that controls the following.

Next, the operation will be explained. First, when starting up the inverter 4, the conductor 1 is turned on with the current limiting resistor shorting switch 202 open, and a limiter is placed in order to prevent rush current to the large capacity filter capacitor 3. The battery is charged through the current resistance 201 for several tens of milliseconds to near the rated value. When the large-capacity filter capacitor 3 is charged, the charging is confirmed and the current-limiting resistor short-circuit switch 20 is
2 and short-circuited both terminals of the current-limiting resistor 2010,
A base signal is applied from the control circuit section 10 to the transistors 41 to 46, and the operation of the inverter 4 is started. At this time, the load current to the load connected to the output of the inverter 4 flows through the current limiting resistor shorting switch 202.

[Problem to be solved by the invention] Since the conventional frequency converter is configured as described above, the charging current flows through the current limiting resistor 201 only at the moment when the conductor 1 is turned on, and normally the main circuit current flows through the current limiting resistor 201. Since the current flows through the short-circuit switch 202, the current-limiting resistor short-circuit switch 20
Since the contact capacity of No. 2 is too high, the structure is naturally large and expensive, and there are problems such as a decrease in space factor.

This invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a frequency converter equipped with a small and highly reliable initial charging device.

[Means to solve the problem]

The frequency converter according to the present invention connects the output of an initial charging device composed of an isolation transformer and a switch to any two phases of a forward converter, and connects the switch and forward converter according to a control command output from a control circuit section. The input side conductor is controlled.

[For production]

The initial charging device in this invention receives power from the auxiliary power supply of the control circuit section, connects the output to two phases of the forward converter, and performs initial charging on the large-capacity filter capacitor, so that the terminal voltage of the large-capacity filter capacitor reaches a predetermined level. When the value is reached, the initial charge is stopped and the conductor of the forward converter is switched on.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same parts as in FIG. 2 are denoted by the same reference numerals. In FIG. ing. The switch 101 is the forward converter 20R phase.

Each is connected to the S phase.

Next, the operation will be explained. First, prior to starting the inverter 4, the switch 101 is turned on via the isolation transformer 102 in response to a command from the control circuit section 10 to charge the large-capacity filter capacitor 3.

In this figure, two diodes 21°25 in the forward converter 2
and diodes 22 and 24 constitute a single-phase rectifier to charge the large-capacity filter capacitor 3.

Further, since the isolation transformer 102 is provided only for initial charging of the large-capacity filter capacitor 3, it may be small. Furthermore, most of the winding impedance of the isolation transformer 1020 is a resistance component, and since its resistance value is large, it has a sufficient current limiting effect during charging. Subsequently, after the completion of charging of the large-capacity filter capacitor 3 is confirmed by the control circuit section 10, the switch 101 is opened by the b command, and the conductor 1 is turned on by the a command, and the main circuit is connected and startup is performed. Therefore, at this point, the rush current to the large-capacity filter capacitor 3 does not pose a particular problem.

In the above embodiment, the protective fuse was omitted from the initial charging device 100 for the large-capacity filter capacitor 3, and the wire-wound resistance of the isolation transformer 102 was used as the current-limiting resistor, but a protective fuse or resistor may be used as necessary. The circuit may be configured to use

Further, in the above embodiment, an example using a transistor inverter has been described, but even when using other semiconductors, the same effects as in the above embodiment can be obtained.

Furthermore, the power supply lead-in phase of the initial charging device is connected to the R phase and S phase of the forward converter.
Although an example has been shown in which each phase is connected, arbitrary two phases may be used. Further, the secondary voltage of the isolation transformer may be set lower than the primary voltage.

〔Effect of the invention〕

As described above, according to the present invention, when initially charging a large-capacity filter capacitor that supplies DC power to an inverter,
The charging power source is connected to any two phases of the forward converter from the control circuit side, which is separate from the main circuit power source, for initial charging, so the device can be configured with only a small switch and an isolation transformer. , and because the inrush current is reduced, the reliability of the inverter and other components is greatly improved. Moreover, since it is small, it can be constructed at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a frequency converter according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional frequency converter. In the figure, 1 is a conductor, 2 is a forward converter, 3 is a large-capacity filter capacitor, 4 is an inverse converter, 10 is a control circuit, 100 is an initial charging device, 101 is a switch, 102
is an isolation transformer. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] In a frequency converter that converts an AC voltage into a DC voltage using a forward converter connected to a conductor, smoothes the DC voltage using a large-capacity filter capacitor, and then converts the DC voltage again into an AC variable voltage using an inverse converter. , an initial charging device consisting of an isolation transformer and a switch connected to any two phases of the forward converter and connected to an auxiliary power supply, and a switch of the initial charging device is turned on, and the terminal voltage of the large-capacity filter capacitor is A frequency converter comprising: a control circuit section that turns off the switch and turns on the conductor when the switch reaches a predetermined value.