Basic information of users
A welded mesh factory mainly produces various welded mesh sheets, fence nets, grassland nets, gabion nets, hook nets, barbecue nets, rabbit cages, etc. The company’s production line equipment is large, medium and small welding machines, and the distribution transformers are 1000 kVA and 1630 kVA transformers. The power supply system diagram is as follows:
Actual operating data
The total power of the welding machine with the 1000KVA transformer is 1860KVA, the average power factor is PF=0.7, and the working fluctuation current is 1050-2700A. The total power of the welding machine with the 630KVA transformer is 930KVA, the average power factor is PF=0.7, and the working fluctuation current The current is 570-1420A.
Power System Situation Analysis
The welding machine power supply is mainly used to step down the large current load, which is a nonlinear load. The equipment generates a large number of harmonics during operation. The harmonic current belonging to the typical harmonic source is injected into the power grid, and the grid impedance generates harmonic voltage, causing the grid voltage and current Distortion affects power supply quality and operation safety, increases line loss and voltage offset, and increases power. Therefore, it is necessary to select system software with harmonic suppression to suppress harmonics, compensate for reactive loads, and improve power factor.
Filter reactive power compensation treatment plan
Governance goals
The design of filter compensation equipment meets the requirements of harmonic suppression and reactive power suppression management.
Under the 0.4KV system operating mode, after the filter compensation equipment is put into operation, the pulse current is suppressed, and the monthly average power factor is around 0.92.
High-order harmonic resonance, resonance overvoltage, and overcurrent caused by connecting to the filter compensation branch circuit will not occur.
Design Follows Standards
Power quality Public grid harmonics GB/T14519-1993
Power quality Voltage fluctuation and flicker GB12326-2000
General technical conditions of low-voltage reactive power compensation device GB/T 15576-1995
Low-voltage reactive power compensation device JB/T 7115-1993
Reactive power compensation technical conditions JB/T9663-1999 “Low-voltage reactive power automatic compensation controller” from the high-order harmonic current limit value of low-voltage power and electronic equipment GB/T17625.7-1998
Electrotechnical terms Power capacitors GB/T 2900.16-1996
Low voltage shunt capacitor GB/T 3983.1-1989
Reactor GB10229-88
Reactor IEC 289-88
Low-voltage reactive power compensation controller order technical conditions DL/T597-1996
Low-voltage electrical enclosure protection grade GB5013.1-1997
Low-voltage complete switchgear and control equipment GB7251.1-1997
Design ideas
Based on the actual situation of the enterprise, the company comprehensively considers the load power factor and harmonic suppression for the filter reactive power compensation of the welding machine, and installs a filter reactive power compensation device on the 0.4KV low-voltage side of the enterprise transformer to suppress harmonics and compensate reactive power to improve the power factor.
During the working process of the welding machine, 3 times of 150HZ, 5 times of 250HZ and above harmonics are generated. Therefore, in the design of the reactive power compensation of the secondary welding machine filter, the frequency of 150HZ, 250HZ and around must be designed to ensure that the filter compensation loop can reasonably suppress the pulse current while compensating the reactive load and improving the power factor.
design assignment
The comprehensive power factor of the production line of the second welding machine matched with the 1000 kVA transformer is compensated from 0.7 to about 0.92. Filtration device Compensation equipment must be installed with a capacity of 550 kVA. The 9 groups of capacitors in phase splitting are automatically connected and disconnected, each of which matches the winding on the bottom voltage side of the transformer. The class adjustment capacity is 25KVAR, which can meet various power requirements of the second-warranty welding machine. The comprehensive power factor of the second-guarantee welding machine matched with the 630 kVA transformer is compensated from 0.7 to about 0.92. Filtration device compensation equipment must be installed with a capacity of 360 kVA. The 9 groups of capacitors in phase splitting are automatically connected and disconnected, each of which matches the winding on the bottom voltage side of the transformer. The class adjustment capacity is 25KVAR, which can meet various power requirements of the production line. This design is sufficient to ensure that the adjusted power factor is higher than 0.92.
Effect analysis after installation of filter compensation
In April 2010, the filter reactive power compensation device of the welding machine was shipped out of the factory. The device automatically tracks the load change of the welding machine, suppresses the harmonic compensation reactive power in real time, and improves the power factor. details as following:
After the filter compensation device is put into use, the power factor change curve is about 0.97 (the raised part is about 0.8 when the filter compensation device is removed)
Load operation
The operating current of the 1000KVA transformer drops from 1250A to 1060A, a reduction rate of 15%, and the operating current of a 630KVA transformer drops from 770A to 620A, a reduction rate of 19%. After compensation, the power loss reduction value is WT=△Pd*(S1/S2)2*τ*[1-(cosφ1/cosφ2)2]=24×{(0.85×2000)/2000}2×0.4≈16(kw h) In the formula, Pd is the short-circuit loss of the transformer, which is 24KW, and the annual saving of electricity expenses is 16*20*30*10*0.7=67,000 yuan (based on working 20 hours a day, 30 days a month, 10 months a year, 0.7 yuan per kWh).
power factor situation
The comprehensive power factor of the enterprise increased from 0.8 to 0.95 in the current month, and the monthly power factor will remain at 0.96-0.98 in the future, and the monthly bonus will be 3000-5000 yuan.
in conclusion
The filter reactive power compensation device of electric welding machine has the ability to suppress harmonics and compensate reactive power, solve the problem of reactive power fines in enterprises, enhance the output capacity of transformers, reduce effective additional losses, increase production, and bring significant economic benefits to enterprises. Return on investment in less than a year. Therefore, the reactive power compensation device manufactured by the company is very satisfied, and will attract many customers in the future.
Post time: Apr-14-2023