JPH03112370A - Power converter - Google Patents

Abstract

PURPOSE:To provide protective coordination between an arm switching element and a fuse by connecting each arm switching element group and a fuse in series, connecting each circulation rectifying element thereof in parallel thereby feeding only the current flowing through the arm switching element to the fuse. CONSTITUTION:At first, a sine wave is compared with a triangular wave in order to produce a PWM signal required for PWM control. A positive pole arm switching element 1 is turned ON in a section of the positive cycle of the sine wave where the triangular wave is smaller than the sine wave, whereas a circulation rectifying element 4 is turned ON in a section where the triangular wave is larger than the sine wave. Next, a negative pole arm switching element 2 is turned ON in a section of the negative cycle of the sine wave where the triangular wave is larger than the sine wave, whereas a circulation rectifying element 3 is turned ON in a section where the triangular wave is smaller than the sine wave. Since approximately identical currents flow through the switching elements 1, 2 and the fuses 7, 8, protective coordination is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power conversion device using a switching element such as a GTO having a self-extinguishing function, and particularly to a fuse suitable for protecting the switching element.

[Conventional technology]

As shown in FIG. 7, a conventional power conversion device is composed of a positive arm switching element 1, a negative arm switching element 2, a snubber circuit 5.6 attached to each, and a freewheeling rectifying element 3.4. A fuse 7.8 is provided between the DC terminal 11.12 and the DC terminal 11.12, which protects the DC power supply from unforeseen destructive currents during normal operation. By combining such am configurations for each phase, an inverter device can obtain alternating current power of any frequency from direct current, supply it to an electric motor, and control its rotation speed.

Due to the circuit configuration, the current flowing through the fuse 7.8 is the sum of the current flowing through the arm switching element and the current flowing through the freewheeling rectifying element.

[Problem to be solved by the invention]

In the above conventional technology, the breaking capacity of the fuse is set to the sum of the continuous allowable rated current of the arm switching element and the continuous allowable rated current of the 3-piece rectifying element, so the fuse breaks against the surge current of the arm switching element. There was a problem in that the capacitance was too large and the arm switching element could not be protected from catastrophic current.

Additionally, arm switching elements for high voltages have been developed as the capacity of power converters increases, but fuses have not been developed to accommodate this, and no consideration has been given to product diversification. However, there were problems in that the standards were limited and the selection range was narrow, forcing the use of products with larger capacities than necessary and high costs.

An object of the present invention is to provide a power conversion device in which protection is coordinated between an arm switching element and a fuse.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inverter device using a power conversion device in which protection is coordinated between an arm switching element and a fuse.

SUMMARY OF THE INVENTION An object of the present invention is to provide a converter device using a power converter in which protection is coordinated between an arm switching element and a fuse.

[Means to solve the problem]

The purpose of the above is to connect in series a group of positive arm switching elements each having a rectifying element for freewheeling connected in parallel, and a group of switching elements of a negative arm having a rectifying element for freewheeling connected in parallel, and to lead the connection point to the AC terminal. , in a power conversion device in which both ends of the arm switching element group are respectively led to DC terminals, each of the arm switching element groups and a fuse are connected in series, and each of the above-mentioned freewheeling rectifying elements is connected in parallel to them. This is achieved by providing a power conversion device.

The purpose of the above is to connect in series a group of positive arm switching elements each having a rectifying element for freewheeling connected in parallel, and a group of switching elements of a negative arm having a rectifying element for freewheeling connected in parallel, and to lead the connection point to the AC terminal. , in a power conversion device in which both ends of the arm switching element group are respectively led to DC terminals, each of the arm switching element groups having fuses connected in series, and the above-mentioned reflux rectifier having fuses connected in series; This is achieved by providing a power conversion device in which the elements are connected in parallel.

The above object is achieved by providing a power conversion device in which the arm switching elements of the plurality of arm switching element groups and the plurality of freewheeling rectifying elements are each connected in series.

The above object is achieved by providing a power converter in which the arm switching elements of the plurality of arm switching element groups and the plurality of freewheeling rectifying elements are respectively connected in parallel.

[Effect]

According to the above configuration, each arm switching element group and the fuse are connected in series, and each freewheeling rectifying element is connected to them in parallel, so that the current flowing through the fuse is limited to the current flowing through the arm switching element. The breaking capacity of the fuse becomes a value corresponding to the surge current of the arm switching element, and protection coordination can be achieved.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 11 is a circuit diagram showing the configuration of one phase of the power conversion device of this embodiment.

First, the configuration of the device will be shown. The positive side consists of a positive arm switching element 1, a snubber circuit 5, a rectifying element 3 for circulation, a fuse 7, and a reactor 9, and the negative side consists of a negative arm switching element 2, a snubber circuit 6, a rectifying element 4 for circulation, and a fuse 8. , reactor 10, the reactor 9 goes to the positive DC terminal 11 which is the power supply side, the reactor 10 goes to the negative DC terminal 12 which is also the power supply side, and the connection point of the positive and negative poles goes to the AC terminal 13 which is the load side. It is connected.

FIGS. 2a and 2b are timing charts showing the relationship between currents flowing through a switching element, for example, GT○, and a freewheeling rectifier of a power converter. First, a sine wave and a triangular wave are compared in order to generate a PWM signal for PWM control. In the positive cycle of the sine wave, the positive arm switching element 1 is turned on in the section where the sine wave is larger than the triangular wave, and the freewheeling rectifying element 4 is turned on in the section where the sine wave is smaller than the triangular wave. Next, during the negative cycle of the sine wave, the negative arm switching element 2 is turned on in the section where the sine wave is smaller than the triangular wave, and the freewheeling rectifying element 3 is turned on in the section where the sine wave is larger than the triangular wave. Become. The AC terminal 13 is connected to the power factor cos? A load current with a phase lag can be obtained.

This figure shows a typical example, and the waveform of the current flowing through the switching element differs depending on the amplitude of the control signal, the phase of the output current and output voltage, etc.

In the conventional power converter shown in FIG. 7, when looking at the average of one cycle of the sine wave of the control signal, the current flowing through the fuse 7 is the sum of the positive arm switching element 1 and the freewheeling rectifying element 3, and the current flowing through the fuse 8 is the sum of the negative electrode arm switching element 2 and the circulating rectifier element 4. Therefore, when trying to protect the positive arm switching element 1 with the fuse 7, it is necessary to determine the breaking capacity of the fuse 7 by adding the current flowing through the free-wheeling rectifying element 3. It is difficult to make the switching element smaller than 2.t. In this embodiment, as shown in Fig. 1, the fuse is connected in series with the switching element, and the freewheeling rectifier is connected in parallel with the fuse, so that the current flowing through the switching element and the fuse is approximately equal, and the current flowing through the fuse is 12·t. It becomes easier to make protection coordination smaller than i-t of the switching element.

Figure 3 shows an example of a fuse that protects the switching element and a fuse that protects the freewheeling rectifying element. Unlike the switching element, the freewheeling rectifying element does not cause overcurrent to flow due to control disturbances, and has been commercialized. Fuses have a long history and stable performance, and there is no strong need for fuses to protect against large surge current resistance, but switching It does not disturb the protection coordination of the elements.

Figure 4 shows an example in which two switching elements and two freewheeling rectifying elements are connected in series in order to increase the power supply voltage and increase the capacity of a power converter. It is necessary to use a product that meets the specifications. Although this embodiment shows a case where two elements are connected in series, the number of elements connected in series is not limited to two, and the effects of the present invention do not change no matter how many elements are connected.

Figure 5 shows that two switching elements and two freewheeling rectifying elements are used to increase the power supply current and increase the capacity of the power converter.
In this embodiment, the fuses are connected in parallel, and it is necessary to use a product with special specifications that can withstand high current. Although this embodiment shows a case in which two elements are connected in parallel, the number of elements connected in parallel is not limited to two, and the effects of the present invention do not change no matter how many elements are connected.

The power conversion device of this embodiment can be applied to either a three-phase inverter or a three-phase converter.

FIG. 6 shows an example in which the power converter of this embodiment is applied to a three-phase inverter, in which DC power is input as a power source and AC power is output to drive the motor 31.

According to this embodiment, the current flowing through the fuse is smaller than the conventional technology due to the freewheeling rectifying element, and it changes with the load power factor, but when considering a three-phase bridge as shown in FIG. The value is given by the following formula.

n cosψ However, cosψ is the load power factor Tokuto A The current flowing through the diode in the system current Say it! Therefore, the capacity of the fuse can be reduced accordingly.

〔Effect of the invention〕

According to the present invention, each arm switching element group and the fuse are connected in series, and each freewheeling rectifying element is connected to them in parallel, so that the 11- current flowing through the fuse is limited to the arm switching element. The breaking capacity of the fuse has a value corresponding to the surge current of the arm switching element, and protection coordination can be achieved.

Furthermore, the effect of reducing the breaking capacity of the fuse to a value corresponding only to the switching element and downsizing the fuse can be obtained.

[Brief Description of the Drawings] Fig. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, Figs. 2a and 2b are timing charts explaining the operation of the circuit shown in Fig. 1, and Fig. 3 is a circuit diagram showing the configuration of an embodiment of the present invention. A circuit diagram showing the structure of another embodiment of the present invention, FIG. 4 is a circuit diagram showing the structure of another embodiment of the present invention, FIG. 5 is a circuit diagram showing the structure of another embodiment of the present invention, FIG. 6 is a circuit diagram of a three-phase inverter to which the present invention is applied, and FIG. 7 is a circuit diagram of a conventional power converter. DESCRIPTION OF SYMBOLS 1... Positive electrode arm switching element, 2... Negative electrode arm switching element, 3... Rectifying element for circulation, 4...
... Rectifying element for freewheeling, 5... Snubber circuit, 6... Snubber circuit, 12- 7... Fuse, 8... 9... Reactor, 1 11... DC terminal, 1 13...・AC terminal, 3 fuse, 0...reactor, 2...DC terminal, 1...motor

Claims (1)

[Claims] 1. A positive arm switching element group in which free-wheeling rectifiers are connected in parallel and a negative arm switching element group in which free-wheeling rectifying elements are connected in parallel are connected in series, and the connection point is an AC terminal. In a power conversion device in which both ends of the arm switching element group are led to DC terminals, each of the arm switching element groups and a fuse are connected in series, and each of the freewheeling rectifying elements is connected to them in parallel. A power conversion device characterized by: 2. Connect the positive arm switching element group in which the freewheeling rectifying elements are connected in parallel and the negative arm switching element group in which the freewheeling rectifying elements are connected in parallel to each other in series, lead the connection point to the AC terminal, and connect the above arm switching element group in series. In a power conversion device in which both ends of the element group are led to DC terminals, each of the arm switching element groups with fuses connected in series and the freewheeling rectifier element with fuses connected in series are connected in parallel. Characteristic power converter. 3. The power conversion device according to claim 1, wherein the arm switching elements of the plurality of arm switching element groups and the plurality of freewheeling rectifying elements are each connected in series. 4. The power conversion device according to claim 1, wherein the arm switching elements of the plurality of arm switching element groups and the plurality of freewheeling rectifying elements are each connected in parallel. 5. An inverter device using the power conversion device according to claim 1. 6. A converter device characterized by using the power converter device according to claim 1.