JPS591358Y2 - Electric furnace load unbalance compensation device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a device that compensates for load imbalance caused by hot water blowing up in an electric furnace.

Figure 1 shows a conventional power supply system to an electric furnace.

In the figure, 1 is an electric furnace, 2 is an electric furnace transformer that supplies power to the electric furnace 1, 3, 4.5 is a power switch, 6,
7.8 is a power bus.

Next, the operation will be explained.

The power supplied from the power buses 6, 7.8 is connected to the power switch 3.
, 4.5 to the electric furnace 1 by the electric furnace transformer 2.

When new raw materials were introduced into the electric furnace 1 while it was in operation, hot water bubbled up inside the furnace, causing a part of the electrode inserted in the electric furnace 1 to become insulated, resulting in load imbalance in each phase. occurs.

As a result, a negative sequence current flows, which has an adverse effect on the power supply side.

However, in the past, the tap changer of the electric furnace transformer 2 was manually operated to lower the voltage applied to the electric furnace 1.
The output was reduced, the moisture contained in the new raw materials was dissipated, and the scale of the hot water blowing was reduced.

When the hot water in the electric furnace 2 has stopped blowing up, the tap changer of the electric furnace transformer 2 is manually operated again to increase the voltage applied to the electric furnace 1, and the output of the electric furnace 1 is returned to normal operation. The situation is being restored.

Conventional measures against hot water boiling up in electric furnaces are taken as described above, so every time hot water blowing up occurs, the tap changer of the electric furnace transformer must be manually operated, and the tap changer must be manually operated. It had the disadvantage of drastically shortening the lifespan of the vessel.

For the electric furnace, the efficiency of continuous operation will decrease,
Furthermore, when the electric furnace is supplied with electric power by a dedicated power supply equipment, there are drawbacks to the power supply equipment, such as repeated sudden changes in load and overheating of extreme parts due to negative sequence current.

This idea was made with the aim of eliminating the above-mentioned drawbacks. When load imbalance occurs due to hot water blowing up in the electric furnace, a dummy load is automatically applied to the optimal phase. To provide a device for compensating for unbalanced loads in power supply equipment by making it appear as if the loads are balanced.

An embodiment of this invention will be described below based on the drawings.

In Fig. 2, 9 is a dummy load, 10, 11.12 is an instrument current transformer that detects each phase current of the electric furnace load, and 13 is an electric furnace load detected by the instrument current transformer 10, 11.12. 14 is a current comparator 1 that compares the current values of each phase.
This is an electromagnetic switch closing device that determines the unbalanced state of the load based on the phase current detected in step 3 and closes the electromagnetic switch 15, 16, 17 of the optimum phase.

20 are instrument current transformers 10, 11, 12, current comparator 13
This is an unbalance detection device constructed by

Note that the other configurations are the same as those of the prior art, so explanations will be omitted.

As described above, this idea is designed to reduce the load on the instrument current transformer 10.11.
2 and the current comparator 13, the detected content is sent to the electromagnetic switch closing device 14, which further judges the detected content and closes the dummy load 9. This system determines the optimum type of electromagnetic switch to be used, and then turns on either the electromagnetic switch 15, 16, or 17 for this optimum type. By adding dummy load 9 for optimization,
Electric furnace load imbalance can be compensated for.

In addition, in this embodiment, it is also possible to provide it in parallel with the electric furnace, and in this way, load imbalance can be compensated for in stages.

Furthermore, if the dummy load amount is controlled using a thyristor, continuously variable load compensation is possible.

As described above, according to this invention, the load imbalance caused by hot water blowing up in the electric furnace is automatically detected, the optimum load is detected, and a dummy load is applied. There is no need to manually operate the tap changer of the device.
This has the effect of suppressing the negative influence on the power source side and also enabling continuous high efficiency operation of the electric furnace.

[Brief explanation of the drawing]

FIG. 1 is a simplified wiring diagram showing a conventional power supply system to an electric furnace, and FIG. 2 is a simplified wiring diagram showing an electric furnace load imbalance compensator according to an embodiment of the invention. In the figure, 1 is an electric furnace, 2 is a transformer for electric furnaces, 3, 4.5 are power switches, 6, 7.8 are power busbars, 9 is a dummy load,
10jlj2 is an instrument current transformer, 13 is a current comparator, 14
is an electromagnetic switch closing device, and 15j6 and 17 are electromagnetic switches. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] An electric furnace transformer that supplies power from a power source to an electric furnace via a switch, an unbalance detection device that detects the unbalance for each phase when the load of the electric furnace is unbalanced, and this unbalance detection device An electric furnace load unbalance compensator comprising a dummy load that is applied to the optimum phase of the load according to a signal from the electric furnace load.