JPH0430167B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in cooling devices for forced cooling type transformers, such as oil feed air-cooled type transformers, and in particular, the invention relates to improvements in cooling devices for forced cooling type transformers such as oil feed air-cooled type transformers, and in particular, the invention relates to improvements in cooling devices for forced cooling type transformers such as oil feed air-cooled type transformers, and in particular, to improve cooling devices for forced cooling type transformers such as oil feed air-cooled type transformers. The present invention relates to a cooling device that is operated.

FIG. 1 is a block diagram mainly showing a cooling device for a conventional oil-feeding, air-cooled transformer. Reference numeral 1 denotes the transformer body, which contains oil as a cooling medium. 2 is the transformer body 1
3 is an oil pump and motor (hereinafter referred to as oil pump motor) that circulates oil as a cooling medium between the transformer body 1 and the cooler body 2; 4 is a fan and motor (hereinafter referred to as fan motor) for cooling the oil sent to the cooler body 2, 5 is a detection unit that detects the load current of the transformer, and 6 is the load detected by the detection unit 5. A control unit that opens and closes the power supply circuit of the oil pump motor 3 and fan motor 4 according to the current value using a switch 7; 8 a no-use breaker (NFB) that opens and closes the power supply for the entire cooling system; 9 a control unit 6; switch 7
A cooler control panel houses the NFB 8, etc., and 10 is a commercial frequency power supply. Note that the oil feed pump motor 3 and the fan motor 4 are induction motors.

FIG. 2 is a block diagram showing the main parts of the cooling device shown in FIG. 1, and shows a case in which three (or three groups) of coolers are connected. In Figures 1 and 2, the solid lines of connection lines between devices and devices are power lines,
The broken line indicates a signal line, and the dashed line indicates a control line to the switch 7, and the same applies to the following figures.

A conventional oil-feeding, air-cooled transformer is constructed as described above, and the cooling device is selected so that the temperature of the transformer is below a specified temperature rise limit under rated load conditions.

However, under light load conditions where the load on the transformer is lower than the rated load, the loss generated by the transformer is lower than under the rated load condition, so even if some coolers are stopped, the temperature of the transformer remains below the specified temperature rise limit. As a result, the power required for operating the cooler (hereinafter referred to as auxiliary equipment loss) can be reduced. For this reason, the number of operating coolers 2 is controlled according to the transformer load current detected by the detection unit 5. FIG. 3 shows an example of a conventional cooler operation control method, in which the control unit 6 determines which of the preset temperature categories the transformer load current I detected by the detection unit 5 is in, and Correspondingly, the switch 7 of the predetermined cooler 2 is closed to reduce the number of operating units N.
control and operate the cooler.

In this case, the cooling capacity of the entire cooling system is approximately proportional to the number of operating coolers, and auxiliary equipment loss can also be reduced approximately in proportion to the number of operating coolers, but reduction of auxiliary equipment loss is not always possible. I can't say it's enough either.

The present invention enables a variable voltage variable frequency inverter to operate an induction motor used in a cooler oil pump motor, fan motor, etc. at variable speed according to the transformer load current, thereby improving the efficiency of the conventional cooling system as described above. The purpose of this invention is to provide a new cooling device that has a greater effect of reducing auxiliary equipment loss.

Fig. 4 is an embodiment of the present invention, and is a block diagram mainly showing a cooling device when applied to an oil-feeding air-cooled transformer, and Fig. 5 shows the main parts of the cooling device shown in Fig. 4. It is a block diagram. In FIGS. 4 and 5, 1 to 5 and 8 to 10 are completely the same as in FIGS. , an arithmetic processing section 13 that receives signals from the interface section 12, determines the power frequency of the oil pump motor 3 and fan motor 4, and outputs the signals; It consists of an interface section 14 with a converter (hereinafter referred to as a variable frequency inverter). Reference numeral 15 denotes a variable frequency inverter that converts the electric power from the commercial power supply 10 into electric power at a frequency determined by the output signal of the arithmetic control unit 11 and supplies the converted electric power to the oil pump motor 3 and the fan motor 4.

In the cooler configured as described above, if the output frequency of the variable frequency inverter 15 is changed,
Since both the oil pump motor 3 and the fan motor 4 are induction motors, their rotational speeds change, and the amount of oil and air blown changes. The cooling capacity of the cooler 2 depends on the amount of oil and air blown, and the shaft power of the oil pump and fan changes approximately in proportion to the cube of the rotation speed, so the output frequency of the variable frequency inverter 15 ultimately Due to the change, the cooling capacity of the cooler 2 and the auxiliary equipment loss change.

Figure 6 shows the drive power frequency F of the oil pump motor 3 and fan motor 4 and the cooling capacity C of the cooler 2.
and shows an example of the relationship between auxiliary equipment loss L,
As shown in FIG. 6, the reduction rate of auxiliary equipment loss with respect to the reduction in drive power frequency is greater than the reduction rate of cooling capacity. Therefore, the auxiliary equipment loss per unit cooling capacity decreases with the drive power frequency.

Therefore, based on the transformer load current detected by the detection unit 5, the arithmetic processing unit 13 determines that the temperature rise of the transformer main body relative to the outside temperature is maintained at a substantially predetermined constant level in the final cooling medium, that is, in the oil-fed air-cooled cooler. If the output frequency of the variable frequency inverter 15 is controlled to obtain the required cooling capacity of the cooler 2 and the corresponding rotational speed of the oil pump motor 3 and fan motor 4, the auxiliary equipment can be Losses can be significantly reduced compared to conventional devices for the following reasons.

In other words, in conventional equipment, the cooling capacity is controlled by changing the number of operating coolers, so both auxiliary loss and cooling capacity are proportional to the number of operating coolers, and the auxiliary loss per unit cooling capacity is In contrast, in this invention, the auxiliary equipment loss per unit cooling capacity decreases with the drive power frequency as described above, so in the light load state of the transformer that can reduce the cooling capacity of the cooler, the loss per unit cooling capacity decreases with the conventional Auxiliary machine losses can be further reduced compared to other equipment.

In addition, in the above embodiment, an oil-feeding air-cooled transformer was described, but it is also possible to use an oil-feeding self-cooling type or an oil-filled air-cooled type transformer that has only either an oil pump motor or a fan motor, or other cooling medium transformers. Similar effects can be expected even if the present invention is applied to an oil-feed water-cooled transformer, for example.

As explained above, this invention is a transformer cooling device that includes a variable frequency inverter and a calculation control section that controls the output frequency of the variable frequency inverter based on the transformer load current detected by the detection section. The auxiliary equipment loss of the cooler can be reduced compared to conventional transformer cooling devices.

[Brief explanation of drawings]

Figure 1 is a block diagram centered on the cooling system of a conventional oil-feeding air-cooled transformer, Figure 2 is a block diagram of the cooling system in Figure 1, and Figure 3 is a transformer load current of a conventional cooling system. Figure 4 is a graph showing the relationship between the number of operating coolers and the number of coolers in operation.
This figure is a block diagram of the cooling device shown in FIG. 4, and FIG. 6 is a characteristic diagram showing the relationship between the drive power frequency of the cooler, the cooling capacity of the cooler, and the loss of auxiliary equipment. In the figure, 1 is the transformer main body, 2 is the cooler main body, 3 is the oil pump motor, 4 is the fan motor,
5 is a transformer load current detection section, 10 is a commercial frequency power supply, 11 is an arithmetic control section, and 15 is a variable voltage variable frequency inverter. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A cooling mechanism that forcibly circulates a cooling medium of a transformer using an induction motor, a current detection unit that detects a load current of the transformer, and a current detection unit that detects a load current of the transformer, and a current detection unit that detects a load current of the transformer, and a current detection unit that detects a load current of the transformer. an arithmetic control unit that determines an output frequency to be supplied to the motor and generates a frequency command signal, and converts the power of the power source into power of a predetermined frequency based on the command signal from the arithmetic control unit, and supplies the power to the induction motor. A transformer cooling device comprising a variable voltage variable frequency inverter, and obtaining a necessary circulating amount of cooling medium by controlling the output frequency of the variable voltage variable frequency inverter. 2. The arithmetic control unit controls the output frequency of the variable voltage variable frequency inverter supplied to the induction motor so that the temperature rise of the main part of the transformer with respect to the ambient temperature of the transformer is almost constant. A transformer cooling device according to claim 1. 3. The transformer cooling according to claim 1, wherein the arithmetic control section controls the output frequency of the variable voltage variable frequency inverter so as to keep the temperature of the main part of the transformer substantially constant. Device. 4. A cooling mechanism in which a cooling medium in the transformer is fan-cooled by an induction motor, a current detection unit that detects the load current of the transformer, and an output frequency that is supplied to the induction motor according to an output signal of the current detection unit. an arithmetic control unit that determines the frequency and generates a frequency command signal, and converts the power of the power supply into power of a predetermined frequency based on the command signal from the arithmetic and control unit,
A transformer cooling device comprising a variable voltage variable frequency inverter that supplies the induction motor to the induction motor, and obtaining a necessary amount of air blown to the cooling medium by controlling the output frequency of the variable voltage variable frequency inverter.