Three-phase pre-charging system

Abstract

The utility model relates to the technical field of power supplies, in particular to a three-phase pre-charging system, which comprises a three-phase power supply unit, a rectifying circuit and a pre-charging circuit. The three ends of the three-phase power supply unit are respectively connected with the input end of the rectifying circuit through power transmission lines, and the rectifying circuit outputs direct current and supplies power to a bus; the pre-charging circuit and the power transmission line are connected in parallel, and the pre-charging circuit and the power transmission line are both provided with switch control parts which are used for controlling the pre-charging circuit and the power transmission line to work alternately. According to the utility model, the charging resistor is connected in series behind the relay to realize pre-charging and reduce impact current, thereby ensuring circuit safety. The pre-charging circuit and the power transmission line are connected in parallel and work alternately, the circuit structure is simple, compared with the mode that the pre-charging circuit is arranged at the rear end of a rectifier bridge, the requirement for the current bearing capacity of a relay in the pre-charging circuit is relatively low, the selectivity of the model type of the relay is larger, and cost is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of power supplies, and particularly relates to a three-phase pre-charging system. Background Art

[0002] Pre-charging refers to the process of performing a short charging with a relatively low current before formal charging. Since the current is too large at the moment of power-on of the three-phase power, it will impact the rectifier bridge, reducing its lifespan, and may also burn out the contact points of the AC contactor switch or the wires.

[0003] In the prior art, the pre-charging circuit is usually arranged at the rear end of the rectifier bridge. Due to the characteristics of the three-phase circuit, the bus current is often slightly larger than the input current. A power relay with a higher current-carrying capacity (exceeding the input current) or multiple relays in parallel are required in the circuit to achieve this.

[0004] Moreover, pre-charging the circuit through a capacitor is a common design scheme. However, when using multiple large-capacity electrolytic capacitors connected in series and parallel for energy storage and filtering, there will also be a relatively large inrush current during charging, and there is still a risk of damaging devices such as the rectifier bridge and fuse.

[0005] Based on the problems in the prior art, the utility model provides a three-phase pre-charging system. Summary of the Utility Model

[0006] The purpose of the utility model is to provide a three-phase pre-charging system to solve the technical problem that in the prior art, the power pre-charging circuit is arranged at the rear end of the rectifier bridge, resulting in a relatively high current in the circuit and posing a safety risk to the circuit.

[0007] The technical solution of the utility model is: a three-phase pre-charging system, including a three-phase power supply unit, a rectifying circuit, and a pre-charging circuit; three terminals of the three-phase power supply unit are respectively connected to the input end of the rectifying circuit through transmission lines, and the rectifying circuit outputs direct current and supplies power to the bus; the pre-charging circuit is connected in parallel with the transmission lines, and both the pre-charging circuit and the transmission lines are provided with switch control components.

[0008] Preferably, two groups of pre-charging circuits are provided, and each group includes a pre-charging switch and a charging resistor connected in series;

[0009] Three groups of transmission lines are provided, and a main switch is connected in series on each group of transmission lines.

[0010] Preferably, the rectifying circuit adopts a rectifier bridge, three terminals of the three-phase power supply unit are respectively connected to the AC input ends of the rectifier bridge, and the output end of the rectifier bridge is connected to the bus; a filter capacitor is connected in parallel at the output end of the rectifier bridge.

[0011] Preferably, the pre-charge switch is turned on, the main switch is turned off, and the charging resistor is in the pre-charge state; the pre-charge switch is turned off, the main switch is turned on, the pre-charge state ends, and the normal working state is entered.

[0012] Preferably, the pre-charge switch is set as a normally open relay.

[0013] Preferably, the main switch is set as an AC contactor.

[0014] Compared with the prior art, the advantages of the present utility model are as follows:

[0015] (1) In the present utility model, a charging resistor is connected in series after the relay to achieve pre-charging, reduce the inrush current, and thus ensure the circuit safety.

[0016] (2) The pre-charge circuit composed of the relay and the charging resistor is connected in parallel between the power supply unit and the rectifier bridge. The pre-charge circuit is connected in parallel with the transmission line and works alternately. The circuit structure is simple. Compared with setting the pre-charge circuit at the rear end of the rectifier bridge, the current-carrying capacity requirement for the relay in the pre-charge circuit is relatively low, the type selection of the relay is more diverse, and the cost is reduced. Description of the Drawings

[0017] The present utility model will be further described below in conjunction with the drawings and embodiments:

[0018] Figure 1 is a schematic diagram of the principle of a three-phase pre-charge system according to the present utility model;

[0019] Figure 2 is a schematic diagram of an embodiment of the rectifier circuit according to the present utility model;

[0020] Figure 3 is a schematic diagram of an embodiment of the three-phase power supply unit according to the present utility model;

[0021] 1. Three-phase power supply unit; 2. Output line; 3. Pre-charge circuit; 4. Rectifier circuit. Detailed Embodiments

[0022] The content of the present utility model will be further described in detail below in conjunction with specific embodiments:

[0023] As Figure 1 shown, a three-phase pre-charge system includes a three-phase power supply unit 1, a pre-charge circuit 3, and a rectifier circuit 4.

[0024] The three terminals (three live wires) of the three-phase power supply unit 1 are respectively connected to the input end of the rectifier circuit 4 through a transmission line 2. The output end of the rectifier circuit 4 is connected to the bus bar, and other circuits, such as a power circuit and a load circuit, are connected to the bus bar. The rectifier circuit 4 rectifies the alternating current into direct current and supplies power to the load at the bus bar end.

[0025] The three-phase power supply unit 1 uses three-phase alternating current, and the specific form refers to the appendix Figure 3 , and the three-phase alternating current provides energy supply to the circuit through a three-phase AC air switch.

[0026] Refer to the appendix Figure 2 , the rectifier circuit 4 uses a rectifier bridge, and filter capacitors are connected in parallel at the output end of the rectifier bridge. The three terminals of the three-phase power supply unit 1 are respectively connected to the AC input terminals of the rectifier bridge, the output end of the rectifier bridge is connected to the bus, and the filtered direct current is output to the bus and the load (not shown in the figure).

[0027] The transmission line 2 corresponds to the three AC output terminals (live wires) of the three-phase electricity, and is provided with three groups. A main switch S3, S4, and S5 is connected in series on each group of transmission lines 2 to control the opening and closing of the transmission line 2.

[0028] The pre-charge circuit 3 is provided with two groups, each group includes a charging resistor and a series-connected pre-charge switch, and the pre-charge switches of the two groups are S1 and S2; each group of pre-charge lines is connected in parallel with two of the transmission lines 2 one-to-one.

[0029] The working process of the three-phase pre-charge system is as follows:

[0030] The pre-charge circuit 3 and the transmission line 2 work alternately.

[0031] Under the normal output state of the power supply, the two pre-charge switches S1 and S2 of the pre-charge circuit 3 are synchronously turned on, and the main switches S3, S4, and S5 are all turned off. The circuit is pre-charged through the charging resistor and is in the pre-charge state.

[0032] When the pre-charge is completed, S1 and S2 are all turned off, and the main switches S3, S4, and S5 are turned on, and the circuit is in the normal working state.

[0033] Among them, the pre-charge switch is set as a normally open relay; the main switch is set as an AC contactor, and when the pre-charge current or voltage reaches a preset threshold, the AC contactor is triggered to close.

[0034] Of course, current and voltage detectors are also provided in the circuit, and the software device or hardware circuit judges whether the threshold is reached according to the current and voltage detection results, and controls the AC contactor to close.

[0035] The utility model connects a charging resistor in series after the relay to realize pre-charging, reduce the inrush current, and thus ensure the safety of the circuit.

[0036] The pre-charge circuit 3 composed of a relay and a charging resistor is connected in parallel between the power supply unit and the rectifier bridge, and works alternately in parallel with the transmission line 2. The circuit structure is simple. Compared with setting the pre-charge circuit 3 at the rear end of the rectifier bridge, the requirement for the current bearing capacity of the relay in the pre-charge circuit is relatively low, the type selection of the relay is more diverse, and the cost is reduced.

[0037] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention. The purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A three-phase pre-charging system, characterized in that: It includes a three-phase power supply unit, a rectifier circuit, and a pre-charging circuit; The three ends of the three-phase power supply unit are respectively connected to the input ends of the rectifier circuit through a power transmission line, and the rectifier circuit outputs direct current and supplies power to the bus; The pre-charging circuit and the power transmission line are connected in parallel, and both the pre-charging circuit and the power transmission line are provided with switch control components.

2. A three-phase pre-charging system according to claim 1, characterized in that: The pre-charging circuit is provided with two groups, each group comprising a pre-charging switch and a charging resistor connected in series; The transmission lines are arranged in three groups, and each group of transmission lines is respectively connected in series with a main switch.

3. A three-phase pre-charging system according to claim 1, characterized in that: The rectifier circuit adopts a rectifier bridge, the three ends of the three-phase power supply unit are respectively connected to the AC input end of the rectifier bridge, the output end of the rectifier bridge is connected to the bus bar; and a filter capacitor is connected in parallel to the output end of the rectifier bridge.

4. A three-phase pre-charging system according to claim 2, characterized in that: The pre-charging switch is turned on, the main switch is turned off, and the charging resistor is in a pre-charging state; The pre-charging switch is turned off, and the main switch is turned on, ending the pre-charging state and entering the normal working state.

5. A three-phase pre-charging system according to claim 2, characterized in that: The pre-charging switch is configured as a normally open relay.

6. A three-phase pre-charging system according to claim 2, characterized in that: The main switch is configured as an AC contactor.

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