JPH02213085A - Dc arc furnace - Google Patents

Abstract

PURPOSE:To ensure the compact design and low cost of a furnace transformer by connecting a high frequency filter to a circuit between the transformer and an SCR rectifier. CONSTITUTION:When a harmonics appears in a system including an SCR rectifier 3 via the phase control thereof in a DC arc furnace 8, a harmonic filter 7 near the rectifier 3 efficiently absorbs harmonic current and restrains the harmonic current flowing to a furnace transformer 1 to a small amount. As a result, the furnace transformer 1 generates less heat and it becomes possible to ensure the compact design and low cost of the transformer 1.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a DC arc furnace.

(Prior Art) Generally, a DC arc furnace for steelmaking has a configuration in which a thyristor rectifier is connected to the secondary side of a furnace transformer, and an electrode is connected to the output side of the thyristor rectifier, and the phase of the thyristor rectifier is controlled. At the same time, the arc current was set at $1110, the electrodes were moved up and down, the arc voltage was controlled at 11, and electric power was supplied to the furnace to melt and refine the scrap.

In order to reduce the harmonics generated due to the above-mentioned phase til control of the thyristor rectifier and reduce the distortion of the power supply voltage waveform, a harmonic filter mainly composed of a capacitor is usually connected to the power supply side of the furnace transformer. It is used as

[Problems to be Solved by the Invention] However, in the above device, the harmonic current generated in the thyristor rectifier section flows through the furnace transformer, so that the iron core of the transformer is heated. Therefore, when using a normal transformer, 't! 60 of the transformer capacity when there is no generation of i harmonics
Transformers that can only be used at ~70% capacity and are designed to include harmonic heating valves are large and expensive.

This invention solves the above conventional problems, and provides a DC arc furnace that can reduce the harmonic current flowing through the furnace transformer, thereby reducing the size and cost of the furnace transformer. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the DC arc furnace of the present invention includes a thyristor rectifier connected to the secondary side of a furnace transformer, and an electrode connected to the output side of the thyristor rectifier. The present invention is characterized in that a harmonic filter is connected between the furnace transformer and the thyristor rectifier.

In the present invention, various types of harmonic filters can be used as the harmonic filter, such as a resonant type or absorption type filter mainly consisting of a capacitor and an axle, and an active filter that supplies a high W4 wave current of opposite phase.

[Effect]

In the DC arc furnace of this invention, harmonics generated in the thyristor rectifier section are reduced by a harmonic filter connected between the thyristor rectifier and the furnace transformer, and a small amount of harmonic current flows through the furnace transformer. is suppressed.

〔Example〕

An embodiment of the present invention will be explained below with reference to FIG.

In the figure, 1 is a furnace transformer, which is connected to an alternating current amm via a switch 2. 3 is a thyristor rectifier for power supply to the electrode 4 (movable electrode), and is connected to the secondary side of the furnace transformer 1. 5 is a furnace body, and 6 is a furnace bottom electrode. Also, 7 is a harmonic filter, furnace transformer 1 and thyristor rectifier 3.
connected between. In addition, an arc current control device that detects the arc N current and controls the phase of the thyristor rectifier 13, a lifting device for driving the electrode 4, and an arc voltage 11JIII that detects the arc voltage and controls the electrode position.
! The illustration of the second class is omitted.

In the DC arc furnace 8 having the above configuration, when harmonics are generated in the system including the thyristor rectifier 3 due to the phase control of the thyristor rectifier 13, the harmonic filter 7 located near the thyristor rectifier FRB 3 efficiently absorbs the harmonic current. However, the harmonic current flowing through the furnace transformer 1 is suppressed to a small amount.

This invention is not limited to the above-mentioned embodiments; for example, a harmonic filter that is inserted in series between a furnace transformer and a thyristor rectifier may be used. It can also be applied to a DC arc furnace for melting and refining metals.

[Effects of the Invention] As explained above, according to the present invention, the harmonics generated in the thyristor rectifier section are effectively reduced by the harmonic filter provided near the thyristor rectifier, which is the source of harmonics. Since the harmonic current flowing through the furnace transformer is suppressed to a small amount, the furnace transformer generates less heat, and the furnace transformer can be made smaller and lower in cost.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of main parts of a DC arc furnace showing one embodiment of the present invention. 1... Furnace transformer, 3... Thyristor rectifier, 4...
... Electrode, 6... Hearth bottom electrode, 7... Harmonic filter, 8... DC arc furnace. Figure 1

Claims (1)

[Claims] 1. Connect a thyristor rectifier to the secondary side of the furnace transformer,
A DC arc furnace in which an electrode is connected to the output side of the thyristor rectifier, characterized in that a harmonic filter is connected between the furnace transformer and the thyristor rectifier.