The Application of Air Water Cooling of Leader High Voltage Frequency Converter and Its Supporting Facilities in Nayong No.2 Power Plant
Screw chiller is called screw chiller because of its key component-compressor. The unit is made of gas refrigerant from the evaporator; after the compressor is adiabatically compressed, it becomes a high temperature and high pressure state. The compressed gas refrigerant is cooled and condensed in the condenser at equal pressure, and after condensing, it changes into a liquid refrigerant, and then expands to a low pressure through a throttle valve to become a gas-liquid mixture. The liquid refrigerant under low temperature and low pressure absorbs the heat of the material to be cooled in the evaporator and becomes gaseous refrigerant again. The gaseous refrigerant re-enters the compressor through the pipeline and starts a new cycle. The principle flow of screw chiller is divided into air cooling and water cooling. Water Cooled Screw Chiller,Screw Water Chiller,Water Cooled Screw Compressor Chiller,screw top water cooler,screw water cooled liquid chiller,water cooled screw chiller trane,Water cooled flooded screw chiller, Screw type water chiller plant‎ Shenzhen Toyocool Refrigeration Equipment Co.,Ltd. , https://www.toyochiller.com
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: 
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: 
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: 
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.