Project Description

Scheme description      

□Application Overview

   Pneumatic technology is one of the most effective means of automation and mechanization of the production process. It has the advantages of high speed, high efficiency, clean safety, low cost, and easy maintenance. The air compressor is the main body of the electromechanical air source device in the pneumatic system. Compressed and pressurized, and then delivered to the pneumatic system, which can be used in metallurgy, textile, electric power, mining, machinery manufacturing, production and processing industries.

□Application Challenge

  Provide high-quality gas supply with low pressure fluctuation;

  Realize energy-saving operation and reduce operating costs;

  Reduce equipment operating noise and improve operating environment;

  Avoid mechanical resonance and improve system stability;

solution:

The load characteristic of the screw air compressor is a constant torque load, and the gas is added to the pipe network through the compression of the screw. In the traditional project, the air compressor motor has been running at a power frequency of 50 Hz, and the air inlet valve is closed when the air pressure reaches the requirement. In unloading operation, the motor at this time is still in the state of power frequency operation, and is doing useless work.

   The control principle of the frequency conversion scheme is: the use of frequency conversion energy-saving technology to reduce the operating frequency of the motor during no-load operation to achieve the purpose of reducing power consumption. The scheme can also achieve soft start of the device, further reduce the starting current, reduce grid impact, and at the same time low frequency The operating noise will also be low, the pressure on each device will be reduced, improve the operating conditions and improve system reliability.

1. Product introduction and application

Related Products

Air compressor dedicated inverter integrated cabinet

• 　　Air compressor energy-saving transformation plan

Dedicated inverter integrated cabinet for air compressor

Product Brief

The air compressor dedicated inverter integrated cabinet is mainly developed for the frequency conversion market of air compressor agents. In the past, most air compressor agents were passively doing air compressor transformation. When customers have demand, they actively request air compressor agents. The main reason is that most air compressor agents do not have the strength for assembly, installation and commissioning or are not large-scale. Now we are introducing an integrated integrated energy-saving cabinet with its own air compressor The drive system does not require major changes to the original system, simple debugging and easy installation.

 Features

　　 More powerful performance

■ Excellent V/F and SVC control performance, large starting torque and stable speed

■ V/F separation, voltage and frequency are adjusted separately, suitable for professional applications

■Integrated chassis design, convenient and fast operation panel, modify parameters at any time according to working conditions, to achieve optimal control

■ There are two modes of speed and torque control, torque mode response is fast, high precision

■ More V/F curve can adapt to more

■ Obvious energy saving effect, in most cases it has a power saving rate of 15% to 45%

　　 Better protection

■ Integrated independent industrial frequency conversion system

■ 41 fault detection codes

■ Self-inspection of equipment around power on, safer

■ Optimize overvoltage stall control and protection, more stable

■ Optional protection action in case of failure, more accurate protection

■ Optimized power supply instantaneous stop judgment function to reduce the probability of false stop

■ Higher hardware redundancy design, more reliable

■ Independent air duct design, effectively solve the heat dissipation problem in the control cabinet

　　 More flexible application

■ Input/output signal type, power common terminal can be selected through jumper (table or diagram)

■ With common DC bus function

■ Rich options and expansion cards: LCD panel, IO expansion card, communication card, etc.

■ PT100, PT1000 interface optional, for detecting motor temperature

■ Compatible with multiple active sensor signals

■ The effective level of the terminal can be defined, the system design is more flexible

　　 Richer functions

■ Multi-function panel, user parameters can be customized

■ Optimized PID control-two-stage PID parameters, etc.

■ New input and output functions: virtual terminal function, analog channel used as digital input, etc.

■ Speed tracking and restart, faster

■ AI curve setting, selection and correction

■ PID reverse cut-off function; AI can be expanded to DI function; parameter backup function

technical parameter

Special inverter for air compressor in BYD factory

　　 Fourth, air compressor energy-saving transformation program and specific analysis

　　》Industry overview

     An air compressor is a device that uses a motor to compress gas in a compression chamber and make the compressed gas have a certain pressure. It is widely used and can be used in various industries such as metallurgy, machinery manufacturing, mining, power, textile, petrochemical and so on. Air compressors account for 15% of the power consumption of large industrial equipment (fans, pumps, boilers, air compressors, etc.). After investigation, most air compressors have the following shortcomings:

1. When the output pressure is greater than a certain value, the load relief valve is automatically opened to make the asynchronous motor idle, which is a serious waste of energy.

2. The asynchronous motor is easy to start and stop frequently, which affects the service life of the motor.

3. Poor working conditions and loud noise.

4. The degree of automation is low, and the output pressure is adjusted by the opening of the artificial control valve. The adjustment speed is slow, the fluctuation is large, unstable, and the accuracy is low.

5. The starting frequency of air compressor power frequency is large, the impact on the power grid is large, the motor bearing wear is large, and the equipment maintenance is large.

In response to the above problems, frequency converters can be used to realize energy-saving transformation of screw-type air compressors. After the transformation, the degree of automation is high and the energy-saving effect is remarkable.

　　》Working principle and control method analysis

     The working principle of the screw type air compressor is shown in the figure below. Air is sucked in through the air filter and the suction regulator valve. The regulating valve is mainly used to adjust the compression chamber formed by the cylinder, rotor and sliding plate. The rotation of the female and male rotors runs eccentrically with respect to the cylinder. The sliding vanes are installed in the rotor slots, and the sliding vanes are pushed to the cylinder wall by centrifugal force. An efficient oil injection system can ensure good cooling of the compressor and minimum comfort consumption of lubricating oil. A thin layer formed on the cylinder wall The oil film can prevent direct contact between metal parts and cause wear. The temperature of the compressed air is high, which is mixed with a certain amount of oil and gas. After separation by the oil and gas separator, the oil and gas is cooled by the oil cooler and then flows back to the oil storage tank through the oil filter. The air passes through the air cooler (air cooling device) ) Cool and enter the gas storage tank.

Control mode analysis

After the frequency conversion of the air compressor, the system should meet the following requirements:

■ The frequency conversion operation state of the motor keeps the outlet pressure of the gas storage tank stable, and the pressure fluctuation range does not exceed ±0.05Mpa.

■ The system has two sets of control loops of frequency conversion and power frequency.

■ The system has two sets of open loop and closed loop control loops.

■ One inverter can control two air compressor units, which can be switched by a changeover switch.

■ According to the working condition requirements of the air compressor, the system should ensure that the motor has constant torque running characteristics.

■ In order to prevent harmonic interference of the air compressor controller, the input end of the inverter should have measures to suppress electromagnetic interference.

■ In the case of small electrical quantity, the motor winding temperature and motor noise should not exceed the allowable range.

■ Considering the future expansion of the system, the inverter should meet the requirements for future expansion of the operating conditions.

　　》System solution selection

The system selects Shenzhen Oulun Electric Co., Ltd. special air compressor special series, has the following characteristics:

■ Frequency accuracy: digital setting is 0.01Hz; analog setting is ±0.1%, which can make the pressure fluctuation range meet the design requirements.

■ Strong overload capacity: 150% rated current 60s; 180% rated current 1s.

■ Stall control function: effectively prevent frequent overcurrent and overvoltage trips.

■ Built-in PID: Closed-loop control system can be easily realized.

■ Torque compensation and lifting function: It has good applicability to the constant torque load of air compressor.

■ AVR function: When the grid voltage changes, it can automatically keep the output voltage constant.

■ Automatic energy saving: automatically reduce the output voltage under light load to achieve energy saving effect.

Installing an input reactor on the input end of the inverter can effectively suppress the interference of the inverter on the power grid. Installing an output reactor at the output end of the inverter can ensure that the motor temperature and noise during low-frequency operation do not exceed the allowable range.

　　》Control electrical diagram & field application

》参数设定

》Benefits

1. Energy saving

     Inverter-controlled compressors are compared with traditional compressors: it is a very economical operating state to adjust the compressor operating conditions according to the air volume demand, and the most significant energy saving effect.

　　 2. Reduce operating costs

     The operating cost of a traditional compressor consists of three items: initial purchase cost, maintenance cost, and energy cost. Among them, the energy cost accounts for about 70% of the operating cost of the compressor. By reducing the energy cost by 30-40%, and the impact on the equipment after the frequency conversion start is reduced, the amount of maintenance and repair is also reduced.

Travel costs will be greatly reduced.

　　 3. Improve pressure control accuracy

     The frequency conversion control system has precise pressure control capability, so that the air pressure output of the compressor matches the air volume required by the user's air system. The output air volume of the inverter control compressor changes with the change of the motor speed. Due to the increased accuracy of the frequency-controlled motor speed, it can keep the system pressure change of the pipe network within ±0.002Mpa, effectively improving the quality of the working conditions.

　　 4. Extend the service life of the compressor

     The frequency converter starts the compressor from 0Hz, and its starting acceleration time can be adjusted, thereby reducing the impact on the electrical and mechanical components of the compressor during starting, enhancing the system reliability, and extending the service life of the compressor.

     In addition, the frequency conversion control can reduce the current fluctuation when the unit starts, and this ripple current will affect the power consumption of the power grid and other equipment. The special inverter for air compressor can effectively reduce the peak value of starting current to the minimum.

　　 5. Low noise of air compressor

     According to the working condition requirements of the compressor, after the frequency conversion energy-saving transformation, the running speed of the motor is significantly slowed down, so the noise of the air compressor during operation is effectively reduced. On-site measurements showed that the noise decreased by about 3 to 7 dB compared with the original system.

　　 6. Take the actual transformation of a single air compressor 22kW in your workshop as an example:

■ The monthly electricity consumption before transformation is approximately:

P moving = U*I*cosφ = 1.732×0.38KV×44A×0.85≈24.62kW

(Cosφ=0.85 grid voltage U=380V air compressor I=44A when operating at 50 Hz power frequency)

■ According to the empirical data, after installing the air compressor inverter, the average current is about 35A:

P variable=U1*I1*cosφ =1.732×0.38KV×35A×0.85≈19.58kW

(Cos=φ0.85 U1=380V I1=35A, upper limit frequency 50Hz, lower limit frequency set between 25-30Hz)

　　Power frequency monthly electricity consumption: 24.62kW×24×26≈15363kW.h

　　 Frequency conversion monthly electricity consumption: 19.58kW×24×26≈12218kW.h

　　 Monthly electricity saving: 15363kW-12218kW≈3145kW.h

　　 Power saving rate: (24.62-19.58)/24.62≈21%

　　 Monthly electricity saving: 3145kW.h×0.75 yuan/kW.h≈2359 yuan

　　Electricity saving electricity cost per year: 2359 yuan × December ≈ 28308 yuan