JPH0420243B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a cooling control device for electrical equipment that drives a cooling device installed in electrical equipment such as a transformer and a reactor using a variable frequency power supply. be.

[Technical Background of the Invention] Electrical equipment such as oil-immersed transformers are cooled by oil-filled air-cooling type cooling control devices or oil-feeding air-cooling type cooling control devices. Conventionally, these cooling control devices Generally, the number of operating units is controlled based on the transformer load or oil temperature.

However, in recent years, from the perspective of energy conservation, it has been reconsidered that the transformer cooling system is cooled more than necessary, which wastes power. Control methods that change according to load, etc. are being considered.

FIG. 1 is a characteristic diagram in which the horizontal axis shows the load factor, and the vertical axis shows the required auxiliary function power factor and the auxiliary machine power factor. In the figure, curve A is an ideal curve of required auxiliary function power with respect to load factor. Curve B is an example of auxiliary machine power in a control system that increases or decreases the number of auxiliary machines according to the load factor, and therefore the cooling capacity of the cooling device is often excessive.

In general, the cooling capacity of a cooling system is approximately proportional to the rotation speed of the fan or pump, and the required auxiliary input is 3 times the rotation speed.
Proportional to the power. Therefore, when the rotational speed of the fan and pump motor is reduced along curve A, the required auxiliary power becomes curves C, D, F, and H, which are compared to auxiliary power curve B based on conventional number control. , the shaded area is obtained as a power saving effect.

[Problems with Background Art] A block diagram of this variable frequency control is shown in FIG. 1 is a transformer, and 2 is a transformer cooling device, which is composed of a fan, a pump, and an electric motor that drives these. 3 is a current transformer that detects the load amount of the transformer 1; 4 is a load factor detector that detects the load factor based on the output of the current transformer; 5 is a control device that controls output power according to the output of the load factor detector 4. variable frequency converter,
11 is a power supply device for the cooling device. The load factor of the transformer 1 is detected by the load factor detector 4, and the output frequency of the variable frequency converter 5 is controlled according to this load factor, and the fan and pump motor rotation speeds of the transformer cooling device 2 are controlled. Change. In the area where the load factor is below I ₂ (the characteristic at this time is point D), the auxiliary function power P ₂
There is no problem with low-speed operation, but when the auxiliary equipment stops and restarts, it is necessary to use the minimum power P ₁ or more that can start the fan and pump motor. For this reason, conventionally, the load factor detector 4 is configured so that the auxiliary power becomes P ₂ as shown by curve E in the region below the load factor I ₂ .

The variable frequency cooling control system constructed as described above has the disadvantage that at low load factors (lower than _I2 in FIG. 1), excessive cooling occurs compared to the ideal curve for required auxiliary equipment.

[Object of the Invention] The present invention was made with the aim of solving the above-mentioned problems, and is an electrical device using variable frequency control that increases the energy saving effect by bringing the auxiliary power closer to the required auxiliary ideal power. An object of the present invention is to provide a cooling control device for

[Summary of the invention] In the present invention, the electric motor of the cooling auxiliary machine stops → starts,
Focusing on the fact that there is a difference in the minimum required auxiliary power between high-speed operation and low-speed operation, the system starts up via a frequency setting device, and after a predetermined period of time, the operation is controlled according to the load factor of the transformer. The idea is to use switching control to compensate for energy loss.

[Embodiments of the Invention] Examples will be described below with reference to the drawings. FIG. 3 is a configuration diagram of an embodiment of a cooling control device for electrical equipment using variable frequency control according to the present invention. In addition,
The same numbers as in FIG. 2 have the same functions. The load factor detector 4 detects curves C and C in FIG. 1 according to the transformer load.
The cooling system auxiliary power (frequency and power) is controlled along D, F, and G. 6 is the setting above the auxiliary power supply frequency that allows the fan and pump motor to start and rotate from a stopped state (equivalent to curve E, the auxiliary power at this time is
_P2 ) is a frequency setting device. 7 is an auxiliary relay, 7a and 7b are normally open contacts and normally closed contacts, 8-P and 8-N are control circuit power supplies, 9 is an operation signal contact for the cooling device, 10 is a time-limited relay, 1
0b is its normally closed contact, and 11 is a power supply device for the cooling device.

In the control circuit of Fig. 4, the load of transformer 1 is
It is detected by the load factor detector 4 via the CT 3 and a control signal is sent to the variable frequency conversion device 5. Variable frequency power supplies convert commercial frequency voltage to direct current,
Outputs control voltage (DC → variable frequency, variable voltage depending on transformer load factor).

The load factor detector 4 detects the curve C depending on the transformer load.
Control the cooling system auxiliary power supply frequency according to In the area below load factor I ₂ , that is, point D on the characteristic curve, there is a low speed rotation limit for the fan and pump motors, and curve G (load factor I ₁ , auxiliary power P ₁ ) indicates that the motor cannot rotate from a stopped state. Unable to start due to lack of torque,
This is the auxiliary power that is at the operational limit when the rotation is gradually controlled from a high-speed rotation state to a low-speed rotation state.

The auxiliary relay 7 and the time-limited relay 10 are energized by the cooling device operation signal 9, and the auxiliary relay 7 is de-energized after a certain period of time (the settling time of the time-limited relay 10). Therefore, when starting the cooling system, the signal from the load factor detector 4 is opened via 7b, and the signal from the frequency setter 6, which is set to enable starting the motor, is input to the variable frequency converter 5 via 7a. do.

Therefore, the characteristic E is determined only during a certain period of time when the cooling control device is activated.
is operated at the set frequency along the curve C,
You will drive along D, F, G.

[Effects of the Invention] As explained above, according to the present invention, it is noted that there is a difference between the minimum rotational frequency of the motor when it is stopped → starting, and high speed operation → low speed operation, and the minimum rotational frequency (stop → Starting)〉Since this is the lowest rotational frequency (high speed → low speed), when the transformer is operating at a low load factor (area below point D), the conventional variable frequency cooling control device is able to switch from stop to start according to curve E due to the frequency constraint. In contrast, it operates on curves D, F, and G along the rotation reduction limit frequency. Therefore, the shaded area surrounded by curve E and curves D, F, and G can be obtained as a power saving effect.

[Brief explanation of drawings]

Figure 1 is a curve diagram showing transformer load factor-required auxiliary function power and auxiliary equipment power, Figure 2 is a block diagram of conventional variable speed cooling control, and Figure 3 is transformer cooling using variable frequency control according to the present invention. FIG. 4 is a configuration diagram of an embodiment of the control device, and FIG. 4 is a control circuit diagram. DESCRIPTION OF SYMBOLS 1...Transformer, 2...Cooling device, 3...CT, 4...Load factor detector, 5...Variable frequency power supply device, 6...Frequency setter, 7, 7a, 7b...Auxiliary relay, 8-
P, 8-N...Control circuit power supply, 9...Cooling control device operation signal, 10...Time-limiting relay, 11...Cooling device power supply device.

Claims (1)

[Claims] 1. In a cooling control device for electrical equipment that controls the cooling capacity of a cooling control device for electrical equipment provided attached to the electrical equipment according to the load of the electrical equipment, a signal corresponding to the load amount of the electrical equipment. A transformer is provided to output the output signal of the transformer, and the output signal of the transformer is inputted, and when the magnitude of the input signal is less than a predetermined value, the minimum power required to maintain the operation of the cooling device is Output the corresponding signal,
A load factor detector that outputs a signal approximately corresponding to the input signal when the magnitude of the input signal is greater than a predetermined value, and a frequency setting that outputs a signal corresponding to the minimum power required when starting the cooling device. The vessel and
A switching means for selectively outputting an output signal of the load factor detector when the cooling device is started and an output signal of the frequency setting device when the cooling device is operating; A cooling control device for electrical equipment comprising a cooling device power supply device whose output signal is controlled according to an input signal.