case of energy-saving transformation of frequency conversion air compressor

The energy-saving transformation of air compressor equipment has been carried out in Quanzhou, Guangzhou, Shenzhen, Zhuhai, Dongguan and other places. The actual energy-saving effect was very satwasfactory. A capacitor film production plant in Quanzhou has been started for 3 months. It has been running for more than 2,100 hours, saving more than 20,000 degrees and saving more than 40%. A 22kW variable frequency air compressor in a hardware factory in Shenzhen operated for 4 months, saving more than 30%.

一、the status of equipment before the transformation

MM company has 2 air compressor rooms to be transformed, all are screw machines, a total of 4 + 3 = 7 air compressors, total power (22 + 37 + 55 + 132) + (110 * 3) = 576kW. Loading and unloading status: 132kW loading time 36 seconds, unloading 50 seconds, loading rate 42%. 110kW was loaded for 65 seconds, unloaded for 55 seconds, and the loading rate was 54%.

Gas pressure demand: spraying demand was 6~7Bar, production workshop demand was 6.8~7.8Bar;

The original system has the following problems:

1 Although the main motor was started by Y-△ decompression, the starting current was still large, which will affect the stability of the power grid;

2 Air compressors often operate at no load, which was non-economical operation and wastes power;

3 The power frequency was very nowasy during operation;

4 The power frequency start has a great impact on the equipment. The operating frequency of each component such as the solenoid valve was high, and the equipment maintenance cost was relatively high.

二、the advantages of frequency conversion

1. Energy saving

The frequency conversion control system can control the output of the air compressor more accurately according to the requirements of the gas system, and achieve the purpose of saving energy:

1) The soft start function of the inverter makes the starting current of the air compressor <2 times the rated current, and the power frequency was up to 8 times;

2) When the air compressor was loaded, the motor speed was changed due to the change of the air supply amount;

3) When the air consumption was very small, the air compressor was unloaded or hibernated, and the energy consumption of the motor was greatly reduced when the air compressor was in the no-load state;

4) V&T frequency conversion starts quickly, and can quickly go out of sleep to enter the loading state, ensuring that the air supply pressure was higher than the lowest value.

2. Reduce maintenance costs

With the variable frequency control system, the soft start of the air compressor reduces the impact on some electrical and mechanical components. During normal operation, the rotational speed was lower than the rated speed for most of the time, which reduces the operating frequency of various related solenoid valves and pneumatic components, prolongs the service life of the components and reduces the maintenance cost of the air compressor.

3. Reduce nowase

When the exhaust volume was reduced, the motor running speed was slowed down, and the nowase emitted by the air compressor was greatly reduced compared with the nowase at full speed operation, which improves the working environment of the operator, was conducive to environmental protection and protects the health of employees.

4. The output pressure was stable, and the output pressure can be kept fluctuating ±0.01Mpa when the gas volume changes slowly.

三、the transformation indicators

1. Pressure stability: normal gas supply, gas tank outlet pressure fluctuation ± 0.05MPa;

2. Control mode: It has two sets of control schemes of frequency conversion and power frequency, which can be switched;

3. Reliability: After any one device was damaged, it can guarantee the short-term recovery of gas supply capacity;

4. Maintainability: After the host was damaged, the backup machine can be put into use. After the host was repaired, the alternate backup machine can be switched online;

5. Starting ability: starting current <2 times rated current, short starting time after sleep, quick air supply, minimum working pressure;

6, online transformation: the transformation does not affect the normal supply of exwasting production gas, unconsciously completed the transformation;

7. The total power saving rate was not less than 20%;

8. Nowase: Less than before the renovation.

The above requirements can be realized by using V5-H frequency drive + special controller. The original air compressor controller was no longer used after frequency conversion transformation. It was necessary to install a pressure transmitter on the compressed air main pipeline, and output 4~20mA signal to the controller, compare it with the pressure set value, output the control signal to the inverter through the PID operation, adjust the motor speed and air compressor. The loading and unloading maintains the pressure to achieve the purpose of constant pressure gas supply.

四、the transformation plan

From the field data, air compressor equipment, renovation construction and future non-stop gas supply maintenance of various factors. The following frequency conversion retrofit solutions can be adopted in two phases:

The first stage: 

Spray air compressor room:

Only 55kW air compressor was used for frequency conversion transformation, 55kW as the main control machine, 55kW as the main engine has been turned on, the power can be adjusted from 0 to 55kW, and can be scheduled 22kW, 37kW, or even 132kW. With this scheme, the gas demand was automatically adjusted within 0~114kW. The 55kW frequency conversion air compressor supports the power frequency mode to improve the anti-rwask ability.

If 55kW, 22kW, 37kW fault or need to be repaired, it can start 132kW to meet the gas supply demand. If the gas supply exceeds 132kW gas supply capacity, start any machine available in 22kW, 37kW, 55kW, starting from the minimum power.

If 22kW or 37kW was set as the host, 22kW, 37kW gas supply capacity was insufficient, 55kW and 132kW will have excess gas supply after opening, which will lead to 55kW or 132kW frequent loading and unloading, return to the old state of power frequency control, and will not be able to Very good frequency conversion energy saving effect.

Top floor air compressor room:

Any two 110kW air compressors can be modified at will, and the third 110kW will not be modified and used for backup.

The two air compressors that have been modified can be used as main engines. When the average production capacity was below, only one machine can be opened. Each unit can be supplied with sufficient pressure independently. During the peak season, two units can be turned on for automatic power dwastribution, which can be quickly reacted when the gas consumption was changed and frequently. The two air compressors are frequency-converted to ensure optimal air supply. If only one 110kW air compressor was used for frequency conversion control, it was worried that when the power was required to be in the range of 110~130kW, that was, the power frequency was full speed, the frequency conversion was the lowest speed or sleep, if the frequency conversion air compressor was always in the dormant critical state, it was used. When the gas suddenly decreases, the upper limit of the pressure will be reached, and the industrial frequency air compressor will be unloaded. Below the lower limit, the power frequency air compressor will restart, which will cause the gas supply to fluctuate. Therefore, it was best to use the power frequency full speed or power frequency shutdown + frequency conversion automatically adjusted within a reasonable power range, so that the control was optimal, the gas supply was the most stable, and the energy saving was the largest. Spraying the machine room, because there are 2 low-power can be fully deployed, so there was no such problem.

The two air compressors that have been modified support the power frequency mode to improve the ability to reswast rwasks. When the fault occurs, the power frequency can be cut back to ensure the same function as before the transformation.

Second stage (optional):

Spray air compressor room:

Change the 132kW standby machine to variable frequency control, so you don't need to open 3 small machines, just use one. It was possible to work in turn instead of keeping the standby machine in standby and the working machine was always working.

Top floor air compressor room:

No second stage renovation was required.

五、Recovery cycle analyswas

Total investment: yuan

Investment recovery cycle: Monthly electricity saving for 0.8 yuan per year: 13.5 million yuan

Total energy saving rate: 27.9%

Total annual energy saving: 16.92 million kWh Estimated total power consumption before transformation: 606,600 kWh/year.

Energy saving rate estimation:

Spray air compressor room: energy saving rate estimate: 30.8%

Loading and unloading status: 132kW, loading rate 42%.

Loading power: 110kW (assumed value, the larger the value, the higher the energy saving rate)

Unloading power: 40kW (assumed value, the larger the value, the higher the energy saving rate)

The air compressor unloading process was actually a process of energy loss. The power that can be saved was basically concentrated in this piece, but After using frequency conversion, you can save 90% of the energy in this part, then the energy saving rate was 30.8%.

(40 × (1-42%)) × 90% ÷ (120 × 42% + 30 × (1-42%)) × 100% = 30.8%

The average load power after frequency conversion transformation was estimated to be: 50kW

 (120×42%+(40×(1-42%))×10%)÷(100%)=52.7kW

Top floor air compressor room: energy saving rate estimate: 19.2%

Loading and unloading status: 110kW, loading rate 54%.

Loading power: 110kW (estimated value, the larger the value, the higher the energy saving rate)

Unloading power: 35kW (estimated value, the larger the value, the higher the energy saving rate, but the equipment should be maintained when more than 60% rated)

The air compressor unloading process was actually a process of energy loss. The power that can be saved was basically concentrated in this piece, but After using frequency conversion, you can save 90% of the energy in this part, then the energy saving rate was 19.2%.

(35 × (1-54%)) × 90% ÷ (110 × 54% + 35 × (1-54%)) × 100% = 19.2%

Estimated average load power after frequency conversion transformation: 61kW

(110×54%+(35×(1-54%))×10%)÷(100%)=61kW

Total energy saving: 169,198 degrees / year, the total annual electricity consumption before the transformation: 606,604 degrees / year, so the overall power saving rate: 27.9%

Calculated at 0.8 yuan per kilowatt hour, annual electricity saving: 169198 × 0.8 = 135358 yuan

The following was the calculation analyswas: according to 4000 hours / year working time, assigned to each machine room was:

Spray air compressor room: 52.7 ÷ (1-30.8%) × 4000 × 30.8% = 93824 degrees

Top floor air compressor room: 61÷(1-19.2%)×4000×19.2%×130%=75374 degrees

130% of the origin: Because the machine room sometimes needs a machine to start at the same time, assuming that the simultaneous opening time accounts for 30% of the total time, when two sets are simultaneously opened, 30% of the single power saving can be increased.

Estimate the total power before the transformation: 52.7 ÷ (1-30.8%) + 61 ÷ (1-19.2%) × 4000 = 606604 degrees

六、after sales service

1. Provide technical training for the management and use of the inverter air compressors of your company.

2, provide 1 year free service, after the failure to repair, respond within 24 hours, provide regular inspection services;

3. After the expiration of the free service, provide regular inspection service, and provide paid service according to the actual situation after the component was damaged.

7. electrical control block diagram