Line control circuit configuration

Patent metadata

Field	Value
Publication number	US-11146067-B2
Application number	US-201816176528-A
Country	US
Kind code	B2
Filing date	Oct 31, 2018
Priority date	Oct 31, 2017
Publication date	Oct 12, 2021
Grant date	Oct 12, 2021

Abstract

A configuration of switches added to a line control circuit allows for switching back and forth between a configuration featuring a series-connected thyristor switch and reactor and a configuration featuring a parallel-connected thyristor switch and reactor. Connecting the reactor in series with the thyristor switch allows a controlled high-impedance circuit configuration that is particularly well adapted for cold furnace start-ups and furnace idling. In this manner, there is reduced need for such equipment as extra startup transformers, alternate low-voltage power supply configurations and temporary specialty electrical apparatus for cold furnace start-ups.

First claim

What is claimed is:

1. A line control circuit comprising:
a supply-side connection point for connecting to an electrical supply;
a load-side connection point for connecting to a load;
a thyristor switch;
a first reactance;
a second reactance; and
a plurality of switches for providing electrical connection of the thyristor switch to the electrical supply and to the load, wherein each switch, independently, is configured for disposition in either a closed condition or an open condition;
wherein the plurality of switches are configurable in and allow for switching between:
a first configuration wherein the plurality of switches are disposed such that:
the thyristor switch is disposed in a parallel combination with the first reactance; and
the parallel combination of the thyristor switch and the first reactance is disposed in series with the second reactance;

and
a second configuration wherein the plurality of switches are disposed such that:
the parallel combination of the thyristor switch and the first reactance is defeated; and
the thyristor switch is disposed in series with a third reactance.

2. The line control circuit of claim 1 wherein the load comprises an electric arc furnace.

3. The line control circuit of claim 2 wherein the electric arc furnace comprises three electrodes.

4. The line control circuit of claim 3 wherein the electric arc furnace comprises six electrodes.

5. The line control circuit of claim 2 wherein the first configuration provides a relatively high power and relatively high current furnace stabilizer.

6. The line control circuit of claim 1 wherein the first reactance is provided by a first reactor.

7. The line control circuit of claim 6 wherein the second reactance is provided by a second reactor.

8. The line control circuit of claim 7 wherein the third reactance is provided by a combination of at least a portion of the first reactor and at least a portion of the second reactor.

9. The line control circuit of claim 7 wherein the third reactance is provided by a third reactor independent of the first reactor and the second reactor.

10. The line control circuit of claim 7 wherein the third reactance is provided by the second reactor.

11. The line control circuit of claim 7 wherein the third reactance is provided by a serial combination of the first reactor and the second reactor.

12. An adapted variable series reactor comprising:
a supply bus connection point for connecting to a phase of a supply bus having a plurality of phases;
a transformer connection point for connecting to a transformer for an electrical load;
a fixed-value reactor connected, at a first fixed-value reactor end, to the supply bus connection point, the fixed-value reactor having a second fixed-value reactor end;
a thyristor-path switch connected, at a first thyristor-path switch end, to the second fixed-value reactor end, the thyristor-path switch having a second thyristor-path switch end;
a thyristor switch connected, at a first thyristor switch end, to the second thyristor-path switch end, the thyristor switch having a second thyristor switch end connected to the transformer connection point;
a tapped reactor connected, at a first tapped reactor end, to the second fixed-value reactor end, the tapped reactor having a second tapped reactor end and a tapped reactor selector;
a tapped-reactor-path switch connected between the second tapped reactor end and the transformer connection point; and
a selector-path switch connected, at a first selector-path switch end, to the tapped reactor selector and, a second selector-path switch end, to the first thyristor switch end;
the adapted variable series reactor having a first configuration defined by:
the selector-path switch being an open state;
the tapped-reactor-path switch being a closed state; and
the thyristor-path switch being in a closed state; and
the adapted variable series reactor having a second configuration defined by:
the selector-path switch being a closed state;
the tapped-reactor-path switch being an open state; and
the thyristor-path switch being in an open state.

13. The adapted variable series reactor of claim 12 wherein the load comprises an electric arc furnace.

14. The adapted variable series reactor of claim 13 wherein the electric arc furnace comprises three electrodes.

15. The adapted variable series reactor of claim 14 wherein the electric arc furnace comprises six electrodes.

16. The adapted variable series reactor of claim 13 wherein the first configuration provides a relatively high power and relatively high current furnace stabilizer.

17. The adapted variable series reactor of claim 12 wherein the second configuration provides a relatively low power and relatively low current furnace startup and idling mechanism.

18. The adapted variable series reactor of claim 12 further comprising a firing angle control device adapted to control a firing angle for thyristors in the thyristor switch.

19. An adapted variable series reactor comprising:
a supply bus connection point for connecting to a phase of a supply bus having a plurality of phases;
a transformer connection point for connecting to a transformer for an electrical load;
a fixed-value reactor connected, at a first fixed-value reactor end, to the supply bus connection point, the fixed-value reactor having a second fixed-value reactor end;
a thyristor-path switch connected, at a first thyristor-path switch end, to the second fixed-value reactor end, the thyristor-path switch having a second thyristor-path switch end;
a thyristor switch connected, at a first thyristor switch end, to the second thyristor-path switch end, the thyristor switch having a second thyristor switch end connected to the transformer connection point;
a further reactor connected, at a first further reactor end, to the second fixed-value reactor end, the further reactor having a second further reactor end;
a lower switch connected between the second further reactor end and the transformer connection point; and
a middle switch connected, at a first middle switch end, to the second further reactor end and, at a second middle switch end, to the first thyristor switch end;
the adapted variable series reactor having a first configuration defined by:
the middle switch being an open state;
the lower switch being a closed state; and
the thyristor-path switch being in a closed state; and

the adapted variable series reactor having a second configuration defined by:
the middle switch being a closed state;
the lower switch being an open state; and
the thyristor-path switch being in an open state.

Assignees

• Hatch Ltd

Inventors

• Campbell Michael Morgan
• Elksnis Yan
• Shen Dong

Classifications

• Y02P10/25

  Process efficiency · CPC title

• H02J3/1807

  using series compensators, e.g. thyristor-controlled series capacitors [TCSC] · CPC title

• H02J3/002 Primary

  Flicker reduction, e.g. compensation of flicker introduced by non-linear load · CPC title

• Y02E40/30

  Reactive power compensation · CPC title

• H05B7/18

  Heating by arc discharge · CPC title