JPH03289362A - Power converter - Google Patents

Abstract

PURPOSE:To reduce the overall size, to simplify the structure and to reduce the cost of a power converter by a method wherein a single resistor serves as an initial charging current limiting resistor and a discharging resistor. CONSTITUTION:A series circuit of a surge absorbing diode 11 and a switch 10 is connected in parallel with a smoothing capacitor 6, which is charged with a DC output from a converter 1 through a switch 4, and a resistor 12 is connected between the joint of the surge absorbing diode 11 and the switch 10 and the converter side terminal of the switch 4. Consequently, a single resistor 12 can serve as an initial charging current limiting resistor and a discharging resistor.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a power conversion device that converts mechanical energy of a load into electrical energy and regenerates it to an inverter. [Prior Art J] Figure 2 is a main circuit configuration diagram showing a conventional power converter of this type. In the figure, 1 is a converter that converts three-phase AC supplied from the power system 2 into DC; A smoothing reactor provided on the DC output side of the converter 1, 4 a switch connected in series with the smoothing reactor 3, 5 an initial charge current limiting resistor connected in parallel with the switch 4, 6 a smoothing reactor 3, A smoothing capacitor connected in parallel with the converter l via a switch 4, 7 an inverter that converts the DC charged in the smoothing capacitor 6 into alternating current, and 8 an inverter 7.
9 is a discharge resistor connected in series with the switch 10 and in parallel with the smoothing capacitor 6, and 11 is a surge absorption diode connected in parallel with the discharge resistor 9. be. It should be noted that the converter 1 and inverter 7 are only shown as single-phase components to simplify the explanation. Next, the operation will be explained. Converter 1 is power system 2
The AC voltage applied from the DC voltage is converted into a DC voltage, and the smoothing capacitor 6 is charged via the smoothing reactor 3 and the initial charge current limiting resistor 5. And this smoothing capacitor 6
When a voltage detector (not shown) detects that the voltage has been charged to a specified voltage, this detection signal closes the switch 4, and from then on, the DC output of the converter l is directly charges the smoothing capacitor 6. The inverter 7 converts the DC voltage charged in the smoothing capacitor 6 into an AC voltage using an inverter frequency signal supplied from a control circuit (not shown), and converts this AC voltage into an AC voltage!
It is supplied to lI8 and driven. When the electric motor 8 is driven, when the inverter frequency becomes lower than the rotational speed of the electric motor 8, the mechanical energy of the electric motor 8 is converted into electric energy and regenerated by the inverter 7. This regenerated electric energy is absorbed by the smoothing capacitor 6, and the charging voltage of the smoothing capacitor 6 increases. On the other hand, since there is a limit to the withstand voltage of the inverter 7, a voltage detection circuit (not shown) detects the terminal voltage of the smoothing capacitor 6, and this detection signal closes the switch 1O to discharge the charge of the smoothing capacitor 6. Discharge occurs through resistor 9. In this case, when the switch IO is turned off, the current tries to continue flowing through the discharge resistor 9 and generates a transient voltage, but this transient voltage is absorbed by the surge absorbing diode 11.

[Problem to be solved by the invention]

Conventional power conversion equipment is configured as described above, and requires two types of resistors: an initial charging current-limiting resistor and a discharging resistor, which increases the size and complexity of the equipment and increases costs. There were issues such as becoming This invention was made to solve the above problems, and by using a single resistor as an initial charging current limiting resistor and a discharging resistor, it is possible to reduce the size, simplicity, and cost. The purpose is to

[Means to solve the problem] The power converter according to the present invention connects a series-connected surge absorbing diode and a switch in parallel with a smoothing capacitor that is charged via a switch with the DC output of the converter, and connects the surge absorbing diode and the switch. A resistor is connected between the connection point and the converter side terminal of the switch. [Effect]

The power converter according to the present invention uses one resistor as both an initial charging current limiting resistor and a discharging resistor.
It is possible to downsize and simplify the device and reduce costs. [Embodiment] An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, in which the same parts as those in FIG.
This is a resistor connected between the connection point P of the switch IO and the converter side terminal 0 of the switch 4. Next, the operation of the above embodiment will be explained. converter 1
converts the AC voltage applied from the power system 2 into DC voltage, and charges the smoothing capacitor 6 via the smoothing reactor 3, resistor 12, and surge absorption diode 11. When a voltage detector (not shown) detects that this smoothing capacitor 6 has been charged to a specified voltage, the switch 4 is closed using this detection signal. Smoothing capacitor 6 directly at the DC output of
to charge. Similar to the conventional device shown in FIG. 2, the inverter 7 converts the DC voltage charged in the smoothing converter 6 into an AC voltage, and drives the motor 8 with this AC voltage. During this drive,
When the inverter frequency becomes lower than the rotation speed of the electric motor 8,
Electrical energy regenerated from the electric motor 8 to the inverter 7 is absorbed by the smoothing converter 6. On the other hand, when a voltage detection circuit (not shown) detects that the terminal voltage of the smoothing capacitor 6 has exceeded the withstand voltage of the inverter 7, this detection signal closes the switch 10, and the charge in the smoothing capacitor 6 is already closed. Discharge occurs through the switch 4, resistor 12, and switch 10. In this case, when the switch 10 is turned off, the current tries to continue flowing through the resistor 12 and generates a transient voltage, but this transient voltage is absorbed by the surge absorbing diode 11. In addition, when the switch 10 is closed, this surge absorbing diode allows the charge of the smoothing capacitor 6 to be directly transferred to the switch 1.
Prevents discharge to zero. In the above embodiment, a diode converter is shown as the converter 1, but it may be made of a transistor, a silice, or the like. Further, although a transistor inverter is shown as the inverter 7, it may be configured with a thyristor or the like.Although a transistor is shown as the switch 1O, a thyristor or the like may also be used. Even without the smoothing reactor 3, the same effects as in the above embodiment can be achieved. [Effect of the Invention J As described above, according to the present invention, one resistor is configured to serve both as an initial charging current limiting resistor and as a discharging resistor, so the number of resistors used is halved. However, it is possible to downsize and simplify the entire device, thereby reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a power converter according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional power converter. l is a converter, 4 is a switch, 6 is a smoothing capacitor,
7 is an inverter, IO is a switch, 11 is a surge absorption diode, and 12 is a resistor. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A converter that converts alternating current to direct current, a switch provided on the DC output side of this converter, a smoothing capacitor that is charged with the DC output of the converter via this switch, and a smoothing capacitor that is charged with the DC output of the converter. an inverter that converts direct current into alternating current and supplies it to a load; a surge absorbing diode and a switch connected in series with each other and in parallel with the smoothing capacitor; a connection point between the surge absorbing diode and switch and the above switching A power conversion device comprising a resistor connected between the converter side terminals of the converter.