JPH0678539A - Cooling system for power conversion apparatus - Google Patents

Abstract

PURPOSE:To prevent a cooling liquid from freezing and corroding apparatuses electrically, by using as the cooling liquid the mixed liquid wherein ethylene glycol is mixed with water, and by making the mixed liquid flow through an ion-exchange resin so as to keep its conductivity low. CONSTITUTION:The mixed liquid wherein ethylene glycol is mixed with water flows from a water tank 6, and passes a pump 7, and further, its one part returns to the water tank 6. Its other part is cooled by a heat exchanger 8, and thereafter, returns to the water tank 6 via the cylinder 9 for an ion- exchange resin. The conductivity of the mixed liquid is kept constant by regulating its flow rate into the cylinder 9 for an ion-exchange resin. The temperature of the mixed liquid is kept constant, adjusting the cooling by the heat exchanger 8 and the heating by a heater 10 in the water tank 6. By such a mixed liquid, a power conversion apparatus is cooled. Therefore, the mixed liquid of a cooling liquid can be prevented from freezing while keeping its conductivity low. Also, even when the operation of the power conversion apparatus used in cold districts is stopped, there is no necessity for the ejection of the cooling liquid and the heat insulation of the cooling liquid or the pipe of the cooling liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling system for power conversion equipment.

[0002]

2. Description of the Related Art An example of a cooling system for power conversion equipment is shown in FIG. The thyristor cooling stack 1, the resistor 2, and the anode reactor 4 are articles cooled with water. These products are connected by insulating piping 5, and water is cooled by flowing between these products.

By the way, since there is a potential difference between the products connected by the insulating pipe 5, a current depending on the potential difference and the resistance of the water in the insulating pipe 5 flows between the products through the water. This current may cause corrosion (hereinafter referred to as "electrolytic corrosion"), and in order to avoid this electrolytic corrosion, a metal, such as stainless steel, that does not easily cause electrolytic corrosion is used at the tip of the part of the article that contacts the insulating pipe 5. At the same time, the cooling water is high resistance water,
So-called pure water is used to keep this current low.

[0004]

When an electric power conversion device using such pure water as a cooling liquid is used in a cold region,
During operation, the cooling liquid is warmed and flowing due to the heat generated by the power conversion device, so that the cooling liquid does not freeze.

However, when the power conversion equipment is stopped due to periodic inspections or accidents, if the outside temperature drops, the cooling liquid may freeze or the insulating pipe 5 may break due to volume expansion. In order to avoid such a situation, the cooling liquid is drained or the cooling liquid or the cooling liquid pipe is kept warm during the stop. However, draining the cooling liquid is a laborious task and is not easy, and keeping the cooling liquid or the cooling liquid pipe warm also requires extra expense. An object of the present invention is to provide a cooling system for a power conversion device that prevents freezing of the cooling liquid and electrolytic corrosion.

[0006]

In order to achieve the above object, the present invention uses a mixed solution of ethylene glycol and water as a cooling liquid by passing it through an ion exchange resin so as to keep the conductivity low. Freezing can be prevented by mixing ethylene glycol, and electrolytic corrosion can be prevented by passing an ion exchange resin.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining a cooling system for a power converter according to the present invention. In FIG. 1, a mixed solution of ethylene glycol and water (not shown), for example, a mixed solution of 31% by weight of ethylene glycol and 69% by weight of water flows in the following loop. That is,
The mixed liquid passes from the water tank 6 through the pump 7, and part of it returns to the water tank 6 as it is, but part of it returns to the water tank 6 through the ion-exchange resin cylinder 9 after being cooled by the heat exchanger 8. The electric conductivity of the mixed liquid is kept constant by adjusting the amount of flowing into the ion exchange resin cylinder 9, and the temperature of the mixed liquid is kept constant by adjusting the cooling by the heat exchanger 8 and the heating of the heater 10 in the water tank 6. . The power conversion equipment (not shown) is cooled by such a mixed liquid.

Further, prevention of freezing and prevention of electrolytic corrosion of the above-mentioned mixed liquid will be described with reference to FIG. 2 and Table 1.
FIG. 2 is a diagram showing the relationship between the concentration of ethylene glycol and the freezing point, and Table 2 shows the mixed solution as described above in a loop as shown in FIG. It shows the content of ethylene glycol in the mixed solution before and after the circulation. In addition,% in the table indicates weight percent.

[0010]

[Table 1]

As described above, in order to keep the electric conductivity of the mixed solution constant, the content of ethylene glycol does not change even when the mixed solution is passed through the ion exchange resin. Therefore, it can be seen from FIG. 2 that the freezing point of such a mixed solution is kept constant at -17 ° C. That is, since the temperature at which the mixed liquid starts to freeze can be greatly reduced from 0 ° C. of water, it is possible to prevent the mixed liquid from freezing even when the power conversion device is stopped. The freezing point of the mixed solution may be adjusted by adjusting the content of ethylene glycol in the mixed solution, that is, the concentration, as can be seen from FIG.

On the other hand, prevention of electrolytic corrosion can be realized by passing an ion exchange resin. Regarding the relationship with anti-freezing, as shown in Table 1, the content of ethylene glycol in the mixed solution does not change even if the mixed solution is passed through an ion exchange resin. Therefore, maintain the freezing point of the mixed solution at a desired temperature. It is possible to prevent freezing.

In this way, it is possible to prevent freezing of the mixed liquid, which is a cooling liquid, while keeping the electrical conductivity low. For this reason,
Even when the power conversion equipment used in a cold region is stopped, it is not necessary to drain the cooling liquid or keep the cooling liquid or the cooling liquid pipe warm, so that the workability can be improved and the cost can be reduced.

[0014]

As described above, according to the present invention, a mixed liquid composed of ethylene glycol and water is passed through an ion exchange resin so as to maintain a low electric conductivity to form a cooling liquid.
It is possible to obtain a cooling system for a power conversion device that can simultaneously achieve prevention of electrolytic corrosion and freezing of a cooling liquid.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a cooling system for a power conversion device according to the present invention.

FIG. 2 is a diagram showing an example of characteristics of ethylene glycol concentration and freezing point.

FIG. 3 is a configuration diagram of a cooling system for a typical power conversion device.

Claims (1)

[Claims] 1. A cooling system for a power conversion device, wherein a mixed liquid of ethylene glycol and water is passed through an ion exchange resin so as to keep the electric conductivity low to form a cooling liquid.