The Application of Air Water Cooling of Leader High Voltage Frequency Converter and Its Supporting Facilities in Nayong No.2 Power Plant

I. INTRODUCTION After the reform of the desulfurization system (FGD) in the thermal power plant, in order to overcome the smoke pressure drop caused by the FGD baffle, absorption tower and internal components, a booster fan, desulfurization gas, is required on the original flue gas side of the FGD. The pressure control system controls the speed of the flue gas fed into the FGD system according to the pressure in front of the original flue gas damper by controlling the static leaf diversion angle of the booster fan, so as to ensure that the pressure of the original flue gas baffle plate is stable and adapts to the boiler Load changes. The booster fan is an adjustable blade axial fan.

II. Overview Nayong Power Plant No.2 Large-scale thermal power generation enterprises currently have a total of four 300MW coal-fired power generation units that use wet desulfurization technology to meet the desulfurization and environmental protection requirements. After the boiler flue gas is dedusted by electric dust, it enters the absorption tower through a booster fan and removes SO2 and SO3. After the subsequent series of chemical reactions and technological processes, the flue gas after desulphurization is finally discharged into the atmosphere to reduce environmental pollution. Nayong Plant began to use frequency conversion in 2010 to meet the national requirements of energy-saving emission reduction targets, of which there are 24 auxiliary machines using energy-saving inverter Harvard-type HARSVEST-VA inverter.

Third, the feasibility of the use of fan frequency conversion The operating characteristics of the fan are as follows:
From the above knowledge, the fan speed was adjusted to reduce the air volume, the fan was changed to run at speed N2, the work characteristic was curve 2, the fan was working at point C, and the air flow was still Q2, but the pressure was H2. Compared with B and C, the reduced axial power of the fan is: ΔP=PB-PC=(H3–H2)×Q2. In the case where the windage resistance characteristics are not changed, the wind volume Q, pressure H, and shaft power P of the fan The relationship between the speed N and the speed N satisfies the following relation (similarity theorem): Q∝N, H∝N2, P∝N3 Therefore, if the wind speed of the fan is changed by the speed control method, the fan shaft power will decrease when the air volume decreases by half.

HARSVERT-A06/485 high voltage frequency converter principle The frequency conversion device adopts multi-level series technology and consists of phase-shifting transformer, power unit and main controller. The structure and electrical performance of each power unit are completely consistent and interchangeable. The structure of the power unit is a basic AC-DC-AC inverter circuit. The rectifier side is a three-phase full-bridge rectifier circuit. PWM control is performed through an IGBT inverter bridge. The output voltage of a single power unit is obtained by stepping sinusoidal PWM waveforms obtained by recombining and superimposing the waveforms of multiple units. This type of waveform has a good sinusoidal degree and a small dv/dt, which can reduce the damage to the insulation of cables and motors. Output filter; colleagues, the harmonic loss of the motor is greatly reduced, eliminate mechanical vibration, reduce the mechanical stress of the bearing and the blade.

In order to fully ensure the reliability of the system, the following main loop solution is adopted:
This scheme is a typical scheme for automatic bypass. The principle is composed of three high voltage switches QF1, QF2 and QF3 and a high voltage switch QF, motor M (see the left figure). QF2 and QF3 closing circuits are required to have mechanical, electrical, and interlocking logic and cannot be closed at the same time. When the inverter is running, QF3 is turned off and QF1 and QF2 are closed. When power frequency is running, QF1 and QF2 are turned off and QF3 is closed. High-voltage switch QF, motor M is the original equipment on site.

Inverter supporting facilities As the HARSVERT-A06/485 high-voltage inverter is composed of phase-shifting transformers, power units and main controllers. The inverter's efficiency is about 96%, theoretically about 4% of the energy is lost. Among them, the primary equipment transformer and power unit account for the main part. If the control loop is neglected, it can be considered that the two most of the losses are about 50%.

The power of the frequency converter used in this booster fan is 4000KW, which is calculated according to 4% of the rated power. Then the heat output during rated operation: 4000KWx4%=160KW, this heat will be lost in the indoor environment of the inverter. In order to ensure the normal use of the equipment, the heat dissipation problem of the equipment needs to be solved. There are the following methods:

1, natural wind cooling. This method has low investment, high environmental requirements, and is greatly affected by the surrounding environment of the equipment. It is not suitable for on-site use where the dust is large and the air is humid, and it cannot guarantee the long-term stable operation of the equipment.

2, using air conditioning cooling. The air-conditioning environment is good. If the air-conditioning cooling capacity is about 2.5KW/P, this equipment is rated by the rated heat value of 160KW, 160KW÷2.5=64 horsepower. It can be concluded that if air-conditioning cooling is used, the purchase of air-conditioning, as well as the long-term operation of the electricity is very large, and the maintenance costs are high.

Compared with the above two methods, the air-cooled system matching device designed by our company can fully solve the problem.

Air cooling system principle:
As shown in the figure, the high-voltage frequency converter operates in a closed room and a hood is installed on the top of the equipment cabinet. The wind produced by FD-1, FD-2, FD-3, FD-4, FD-5 and FD-6 The tube leads to the heat that is dissipated from the top of the cabinet of the high-voltage converter, and a booster fan is installed outside. After passing through the FD-7 (water cooler) installed in the wall, the cooling air is circulated to the high-voltage inverter room again for the high-voltage inverter. The body is cooled.

For the use of air conditioners, the cost of cooling is extremely low and investment is not significant. Only need to provide circulating cooling water of FD-7 and a low-voltage motor for circulating the pressure in the air duct. Environmental sanitation, high cooling efficiency, long-term investment, and easy maintenance.

After summarizing the use of high-voltage frequency conversion devices, according to the user's rough statistics, the normal load operation reduces the current by about 50A compared with the industrial frequency operation. Especially at low load operation, the effect is particularly obvious, and the power grid impact and mechanical impact caused by the start of the power frequency are significantly reduced. , Reduce motor maintenance two, save inspection and maintenance costs, while the life of the motor is greatly extended.

Tri Clamp concentric reducers, as their name implies, reduce in diameter towards the center thus forming a conical cylinder. A Concentric Reducer is often used inline on a vertical flow application, or if laid horizontally, as an increaser. We do not recommend reducing in the horizontal as pooling may occur. In these cases, an Eccentric Reducer, which lays flat on one side is preferable. Concentric reducers have a lower chance of producing agitation like an end cap reducer may.


Tri Clamp eccentric reducers are designed primarily to reduce in a horizontal flow application. Because they are flat on one side, their is no risk of pooling, unlike their concentric reducer counterparts.They are also well suited when one end is offset from the other in a vertical position. They are designed to be inserted inline and have a lower chance of producing agitation.


1.Connection mode: Clamp,Weld

2.Specification: 1/2"-4", applied to the stainless steel pipeline system

3.Material: SS304, SS316L

4.Standard: ISO, DIN, SMS, 3A etc

5.Application: Beer, food, dairy, beverage, cosmetics, pharmacy etc industries


Sanitary Reducer


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Sanitary Butterfly Valve, Sanitary Check Valve and Diaphragm Valves, as well as Various Tank Accessories:  Sight Glass, Strainers/Filter, Cleaning Ball, And other Pipe Fittings , (Pipe Unions: SMS, DIN, IDF, RJT, 3A,DS; Fittings: Ferrule,Elbow, Tee, Reducer and all other Non-standrad fittings), each products are tested well by our strictly Quality Control System, and we also have excellent service to support you and promote your business.
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Any question or problem will be respond within 12 hours.

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