Arc furnace power supply with resonant circuit

Patent metadata

Field	Value
Publication number	US-11658585-B2
Application number	US-202017622439-A
Country	US
Kind code	B2
Filing date	May 8, 2020
Priority date	Jun 27, 2019
Publication date	May 23, 2023
Grant date	May 23, 2023

Abstract

A power supply system for an electric arc furnace includes an AC input connectable to an electrical grid and an AC output for supplying at least one power electrode of the arc furnace; a resonant circuit interconnected between the AC input and the AC output. The resonant circuit includes a controllable bypass switch for connecting and disconnecting a circuit input and a circuit output of the resonant circuit and a capacitor and a main inductor connected in parallel with the bypass switch.

First claim

The invention claimed is:

1. A power supply system for an electric arc furnace, the power supply system comprising:
an AC input connectable to an electrical grid and an AC output for supplying at least one power electrode of the arc furnace; and
a resonant circuit interconnected between the AC input and the AC output;
wherein the resonant circuit comprises a controllable bypass switch for connecting and disconnecting a circuit input and a circuit output of the resonant circuit;
wherein the resonant circuit comprises a capacitor and a main inductor connected in parallel with the bypass switch; and
wherein the power supply system comprises a controller for controlling the bypass switch, such that a circular current is formed in the resonant circuit, when the bypass switch is closed, which lowers a current through the power supply system.

2. The power supply system of claim 1 , wherein a further inductor is connected in series with the bypass switch between the circuit input and the circuit output.

3. The power supply system of claim 2 ,
wherein the further inductor is connected in parallel with the capacitor and the main inductor; and/or
wherein the capacitor and the main inductor are connected in series.

4. The power supply system of claim 2 , wherein the main inductor has a higher inductance as the further inductor.

5. The power supply system of claim 1 ,
wherein the bypass switch is composed of semiconductor switches; and/or
wherein the bypass switch is a bidirectional switch.

6. The power supply system of claim 1 ,
wherein the bypass switch comprises two anti-parallel semiconductor switches; and/or
wherein the bypass switch comprises two anti-parallel thyristors.

7. The power supply system of claim 1 , further comprising:
a transformer interconnected between the AC input and the resonant circuit; or
a transformer interconnected between the resonant circuit and the AC output.

8. The power supply system claim 1 , further comprising:
a harmonic filter interconnected in the AC input;
wherein the harmonic filter comprises at least two filter components, each of which comprises a filter capacitor and a filter inductor and each of which is adapted to another higher order harmonic of an AC input voltage.

9. The power supply system claim 1 , further comprising:
an active inductive reactor interconnected into the AC input, wherein the active inductive reactor comprises a bypass switch and an inductor connected to the AC input; and/or
a compensating converter interconnected into the AC input;
wherein the active inductive reactor and/or the compensating converter are controlled to minimize a flicker in the AC input.

10. The power supply system claim 1 ,
wherein the AC input has at least two phases and/or the AC output has at least two phases; and
wherein a resonant circuit is interconnected in each phase of the AC input and/or in each phase of the AC output.

11. A method for controlling a power supply system claim 1 , the method comprising:
determining an electrode current supplied to the at least one electrode; and
controlling the bypass switch, such that the electrode current is adjusted to a defined current, wherein a circular current is formed in the resonant circuit, when the bypass switch is closed, which lowers a current through the power supply system.

12. The method of claim 11 , wherein a duty cycle of the bypass switch is adjusted to control the electrode current.

13. The method of claim 11 , further comprising:
detecting an overvoltage and/or a surge current in the resonant circuit; and
protecting the resonant circuit with the bypass switch, when an overvoltage and/or a surge current is detected, by opening and/or closing the bypass switch.

14. A controller for an electric arc furnace with a power supply system according to claim 1 .

15. An electric arc furnace, comprising:
a power supply system according to claim 1 ;
a vessel for receiving metal material; and
power electrodes for melting the metal material, when supplied with current from the power supply system.

Assignees

• Abb Schweiz Ag

Inventors

• Steimer Peter Karl

Classifications

• Y02P10/25

  Process efficiency · CPC title

• H02M5/12 Primary

  for conversion of voltage or current amplitude only · CPC title

• H05B7/148

  Automatic control of power (electrode feeding arrangements H05B7/109; automatic feeding of electrodes for spot or seam welding or cutting B23K9/12; disposition of electrodes in or on furnaces F27D11/10; control of position in general G05D3/00; regulating electric characteristics of arcs in general G05F1/02; regulating electric power in general G05F1/66) · CPC title

• H05B7/144

  Power supplies specially adapted for heating by electric discharge; Automatic control of power, e.g. by positioning of electrodes · CPC title

• H02M5/06 Primary

  using impedances · CPC title