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Hiconics 10kV/10000kW water cooled drive used in North Korea power plant

Number of visits: Date:11/19/2015 03:22:54

Hiconics Large Power Water-Cooled Medium Voltage Drive

1.      Technical Background

Medium Voltage drives will cause power consumption when running, normally the power consumption is 3-5% of the drive’s capacity, among which phase-shifting transformer takes up 45%, rectifier and converter takes up 40%, control system, main circuit cable and copper bar all together takes up 15%.

There are three modes of cooling of MV drive, including natural cooling, air force cooling and water cooling. In China market, mainly the air forced cooling is the most popular one. With the development of MV drive technology, the VFD capacity has been continuously enlarged, and the air forced cooling cannot fully meet the cooling requirements of the large power drives because air forced cooling affected by heat sink size, environment temperature, ambient temperature, fan size, noise and etc.

Cooling is the major factor that affects the reliability of MV drives. The heat produced from the large semi conductor components and phase shift transformer will cause the temperature rise of these components. If there is no proper cooling to take the heat away, then it will cause the component temperature rise higher than their required junction temperature. Therefore, in the design process, select the proper cooling mode and with proper design, in this way, the life cycle of the components can be effectively prolonged and thus the reliability of VFD improved.

2.      Comparison between water cooling and air cooling

Water cooling

Air forced cooling

Coefficient of heat transfer 3500W /(m2·℃), good cooling effect

Coefficient of heat transfer 35W /(m2·℃), cooling effect not as good

Smaller sized VFD, compact structure, saving space

big size, big footprint

Less noise, good operation environment, the major driving power parts (eg. water pump) one for use, one for spare, high reliability 

fan in the VFD, with the VFD power growing, the number of fans should be increased, high noise level, and fan life cycle is limited, less reliable.

Not limited by the space, because the distributing pipe lines are not limited by the distance, and smaller size. 

VFD cannot be installed too far away, because the wind pipe transmission distance should not be too far, or else the fan wind pressure will be larger

Able to cool down the system temperature lower than the room temperature, not limited by the room temperature

cooling ability limited, not able to cool down the system temperature lower than room temperature

Not affected by the environment, able to run in the environment with dust and harmful gas

the dust and harmful gas will adhere to heat sinks, increase thermal resistance, thus affecting the heat exchange and electric isolation

Applicable to all types of VFDs, especially to the large power VFDs and the harsh environmental site

Cooling effects is not as good as water cooling effects for large power VFD

3.      Hiconics water-cooled VFD structure and cooling principle

3.1 VFD structure

Water cooled VFD is composed of start cabinet, phase shift transformer, power cell cabinet, control cabinet and circulating water cooling units. Compared with air forced cooled VFDs, circulating water cooling units are the new parts, the other structure are the same. (see figure 1)

1. start cabinet  2. Phase-shift transformer 3. power cell cabinet 4 control cabinet  5. Circulating water cooling units

3.2 Working principle of water cooling units

3.2.1 Working principle of water cooling diagram  (see figure 2)

3.2.2 Description of water cooling

Driven by the main circulating pump, the cooling water is flowing through the power cell heat sink with a constant speed, taking the heat away continuously; the cooling water get temperature rise, and they will go through the main circuit to enter the heat exchanger to do the heat exchange; after heat exchange, the water will flow back to the entrance of the main circulating pump, and form an enclosed circulating cooling system.

Water cooling control modules automatically regulates the heat exchange proportion according to the preset cooling water temperature value to precisely control the water temperature. According to the water cooling capacity, and various onsite conditions, the system can adopt the secondary heat exchange mode such as water-water, water-air etc. to release the heat to the outside environment.

4.  Hiconics water-cooled VFD solution

4.1 Transformer

4.1.1 Structure (see figure 3)

4.1.2 Working principle

   Type: forced oil-immersed circulating cooling water transformer

Transformer oil tank, oil-water heat exchanger, oil pump use pipes connected in series to form an enclosed circuit. When transformer is working, it produces heat, transformer is immersed in the cooling oil, heat transferred to cooling oil. Due to the oil pump working, it forces  the cooling oil to flow, the heated oil flowing out through the upper part of the oil tank, and going through the enclosed piped and do the heat exchange with cooling water when passing by the oil-water heat exchanger. The heat in the hot oil taken away by the cooling water, the oil after being cooled return back to the oil tank, in this way of circulating, the transformer cooling has been achieved.

4.1.3  Features

Ø  Cooling type: oil-water heat exchange

Ø  less loss, efficiency >99%

Ø  high over-voltage capability, capacity less than 1,5 times, continuously running for 120 minutes.

Ø  using patented technology, to ensure the reliable sealing of wire tap.

4.2 Power cell (see figure 4)


4.2.1 cooling mode: power cell using water cooling mainly, air forced cooling as supplement

4.2.2  Solution and feature

Ø  power cell water cooling pipes using paralleled connection, to ensure the even distribution of flow.

Ø  independent power cell electrolytic capacitor cooling wind channel, low capacitor running temperature, long life cycle.

Ø  ;using laminate busbar design, small parasitic inductance, compact structure of power cell

Ø  power cell heat sink uses Vacuum brazing type water cooling radiator, the water inlet entrance and water return entrance use double quick joint closure, easy for the replacement of power cells.

Ø  power cell cabinet main pipes use stainless steel pipes, power cell and main pipes connection using rubber hose to ensure the power cell isolation

4.3  Circulating cooling water units

4.3.1  circulating principle (see figure 5)

 Figure 5

4.3.2 Working principle

Driven by the main circulating pump, the cooling water flows through the power cell heat sink with constant speed, continuously taking away the heat. After cooling water temperature rise, it passes the main pipe circuit and enters in the heat exchange device to do the heat exchange. After the water temperature lowered, return back to the entrance of the main circulating pump and form an enclosed circulating cooling water system. The system control module regulates the heat exchange proportion according to the preset cooling water temperature, control precisely the water temperature.

According to the difference of cooling capacity, onsite condition, the system can adopt water-water, water-wind heat exchange mode to release the heat to the outside environment.

Because the MV drive runs under the high voltage environment, the cooling water must have high resistivity, the main circulating cooling circuit paralleled connected with de-ionized water treatment bypass, a certain proportion of cooling water flows through the ion exchange, continuously removing the ions extracted from the equipment and pipes. To keep the constant pressure of pipes and cooling water full, and to buffer the change of cooling water size caused by the temperature exchange, the buffer tank and the water supply device is installed.

4.3.3 Features:

Ø  all of the devices in the pipe circuit use stainless steel, good anti-corrosive

Ø  independent de-ionized water treatment bypass device.

Ø  independent PLC supervision system to achieve the remote control

Ø  Full scale prewarning protection function. Eg: water leakage monitoring and alarm, condensation monitoring and control, water constant temperature control and high water temperature alarm, water conductivity monitoring and alarm, etc.

5.      Onsite running condition

Ø  installed in independent enclosed space, equip the air conditioner according to the VFD capacity, air conditioner power selection formula:

Pair conditioner =(PVFD(kVA)*1%/2.5,(hp)

Ø  Onsite provide 5-32℃cooling water, the flow quantity is related to the VFD capacity. If there’s no cooling water supply onsite, Hiconics can supply secondary cooling water equipment.

Industry: Company News

Keywords for the information:

Hiconics Drive Technology Co., Ltd.    Tel: +86 10 59180173    Fax: +86 10 59180035

Address: No.3 Bo Xing 2nd Road, Economic Technology Development Zone, Beijing.

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Tel: +86 10 59180173