JPS636212Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an operation control device for a heat retention furnace in a steel rolling facility, and particularly to an emergency operation circuit during a commercial power outage.

A heat retention furnace is a type of self-heating reverberatory furnace that aims to retain the heat of the heat material sent to the rolling mill (it retains heat by reflecting the heat of the heat material itself inside the furnace). It is. A roller table is installed inside the furnace, and the heat material is moved by the motor drive of the roller table.

If a power outage occurs during operation, the roller table will stop and the heating material will be in a stationary state, causing thermal damage to the rollers in that area. To prevent this, in the event of a power outage, the system switches to emergency power and repeatedly moves the heating material back and forth at a slow speed inside the furnace.

Generally, the driving means for a roller table is as follows:
A variable speed control device is used, such as a combination of a DC motor and a thyristor Leonard device, or a combination of an induction motor and a VVVF (Variable Voltage Variable Frequency) device. An example is shown in FIG.

In Fig. 1, 1 is a commercial power supply, 2 and 3 are circuit breakers, 4 is a forward conversion circuit using a thyristor, 5 is a control device, 6 is a DC reactor, 7 is a DC motor for driving the roller table, and 8 is a DC motor for driving the roller table. A pulse pickup 9 detects the rotational speed of the motor 7 and supplies it to the control device 5; 9 detects the motor current and supplies it to the control device 5;
The controller 5 controls the gate phase of the thyristor 4 to control the motor 7.
variable speed control. In the event of a power outage, the system will switch to an emergency power source (not shown) and control the system to repeatedly move forward and backward at slow speeds.

However, although there is generally a speed difference of 10:1 or more between the operating speed during normal operation and the slow forward/backward speed during emergency operation, the installed capacity remains the same in either case as long as the operation is performed at the same voltage. That is, even during a power outage, a power source with the same power capacity as in normal operation is required.

This invention was made taking the above points into consideration.
A transformer is installed to step down the voltage of the emergency power supply, and in the event of a power outage, the control device is connected to the primary side and the main circuit is connected to the secondary side, making it possible to reduce the capacity of the emergency power supply and operate with a high power factor. The purpose of the present invention is to provide an operation control device for a heat retention furnace.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 2 shows an embodiment of the present invention, in which 1 is a commercial power supply, 2, 3, and 10 are circuit breakers, 4 is a forward conversion circuit using a thyristor, 5 is a control device, 6 is a DC reactor, and 7 is a DC motor, 8 is a pulse pickup, 9 is a current detector, 11 is an emergency power supply,
12 is a transformer that steps down the voltage of this power supply 11;
3 is a switching circuit using an electromagnetic contactor, and contact 13
A switches the connection between the commercial power source 1 of the main circuit and the secondary side of the transformer 12, and a contact 13B switches the connection between the commercial power source 1 of the control device and the primary side of the transformer 12. . The transformer 12 has a transformation ratio of, for example, 1/10.

With such a configuration, normally the contacts 13A,
13B is in the illustrated state, and is connected to the main circuit and the control device 5 to the commercial power source 1 side, and is controlled by the control device 5 to a required speed.

On the other hand, during a power outage, the contact 13A of the switching circuit 13,
13B is switched, the main circuit is connected to the secondary side of the transformer 12, and the control device 5 is connected to the primary side of the transformer 12. In this state, the controller 5 controls the vehicle to repeatedly move forward and backward at a very slow speed. For example, it is driven at 1/10th the normal speed. In this case, transformer 1
2 reduces the voltage of the emergency power supply 11 to 1/10, and the thyristor 5 performs speed control without extremely restricting the speed. In other words, high power factor operation occurs. For example, when a 75KW DC motor is operated using the thyristor Leonard method, the output is approximately 113KVA at normal rated speed operation, which is 1/10 at the same voltage.
The speed is approximately 113KVA, but the power supply voltage is reduced to 1/10 and operated using the thyristor Leonard method.
When the speed is 1/10, it is approximately 11.3KVA, that is, 1/1
A capacity of 0 is sufficient.

FIG. 3 shows another embodiment of the present invention, in which an induction motor 14 is used instead of the DC motor 7, an inverse conversion circuit 15 is arranged on the output side of the DC reactor 6, and the speed is controlled by a so-called VVVF device. This is a case where control is performed, and the effects such as high power factor operation are the same as in the previous embodiment.

Note that the transformer 12 may be an autotransformer.

As described above, according to the present invention, a transformer is provided to step down the voltage of the emergency power supply, and the stepped down low voltage is supplied to the main circuit in the event of a power outage. It can be performed using a high-capacity power supply (the control device requires conventional voltage, but the power required for control is negligible), and during forward conversion, phase control can be performed using conventional low power factor power. This is different from the operation and is in the range of high power factor operation, which is very preferable for the generator as the power source 11 and becomes a load. Another advantage is that it can contribute to solving general phenomena in which the influence of the thyristor device as a load on the AC synchronous generator on the damper winding becomes a problem.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram showing an example of a conventional operation control device for a heat retention furnace, Fig. 2 is a connection diagram showing an embodiment of the present invention, and Fig. 3 is a connection diagram showing another embodiment of the present invention. It is. DESCRIPTION OF SYMBOLS 1...Commercial power supply, 4...Forward conversion circuit, 5...Control device, 7...DC motor, 11...Emergency power supply, 12...
Transformer, 13...Switching circuit, 14...Induction motor, 1
5... Inverse conversion circuit.

Claims (1)

[Scope of utility model registration request] In the operation control device of a heat retention furnace, which has a control device that variable speed controls the drive motor of the roller table that moves the heat material, and which is normally connected to the main circuit and the control device to the commercial power source, and switches to the emergency power source in the event of a power outage. , a transformer that steps down the voltage of the emergency power supply, and the main circuit and control device are usually connected to the commercial power supply, and in the event of a power outage, the main circuit is connected to the secondary side of the transformer, and the control device is connected to the primary side of the transformer. A heat retention furnace operation control device comprising a switching circuit connected to each.