Traditional air compressor transformation principles and advantages after transformation

Problems with traditional air compressors

1. Serious waste of electric energy.

Traditional loading and unloading air compressors, energy is mainly wasted in:

(1) Power consumption during loading. After the pressure reaches the required working pressure, the traditional control method determines that the pressure will continue to rise by about 10% until the pressure is unloaded. During pressurization, more heat and noise are bound to be generated, resulting in loss of electrical energy. On the other hand, before the high-pressure gas enters the pneumatic components, its pressure needs to be reduced through the pressure reducing valve, and this process also consumes energy.
(2) Power consumption during unloading. When the unloading pressure is reached, the air compressor will automatically open the unloading valve, causing the motor to run idly, causing serious energy waste. The power consumption of the air compressor when it is unloaded is about 30% to 50% of that when it is fully loaded. It can be seen that the traditional air compressor has obvious energy-saving space.

2. The power frequency start-up impulse current is large.

Although the main motor is started by Y-△ decompression, the starting current is still very large, which has a great impact on the power grid, which may easily cause the instability of the power grid and threaten the operation safety of other electrical equipment. For self-generating plants, the impact of several times the rated current may cause abnormalities in other equipment.

3. The pressure is unstable and the degree of automation is low.

The traditional air compressor has a low degree of automation, and the adjustment of the output pressure is realized by the control of the loading and unloading valve and the regulating valve. The adjustment speed is slow, the fluctuation is large, the precision is low, and the output pressure is unstable.

4. A large amount of equipment maintenance.

The starting current of the air compressor at power frequency is large, up to 5~8 times of the rated current. The working method determines that the loading and unloading valve must move repeatedly, the components are easy to age, the power frequency runs at high speed, the bearing wears heavily, and the equipment maintenance requires a lot.

5. Loud noise.

Continuous high-speed operation at power frequency, additional pressure exceeding the required working pressure, repeated loading and unloading, all directly lead to high noise at power frequency operation.

Transformation principle

According to the original working conditions of the air compressor and combined with the requirements of the production process, after the frequency conversion technology transformation of the air compressor, the system meets the following requirements.

1. After the air compressor is transformed, the system is switched by a switch, with two sets of control loops of frequency conversion and power frequency, and two sets of control loops of open loop and closed loop. When one drive two starts, for the two motors M1 and M2, the frequency conversion/power frequency start can be selected through the switch. During normal operation, the motor M1 is in the state of variable frequency speed regulation, and the motor M2 is in the state of power frequency. The on-site pressure transmitter detects the outlet pressure of the pipe network and compares it with the given value. After the PID command operation, the frequency signal is obtained, and the speed is adjusted to reach the required pressure. When stopping, press the stop button, PLC controls all contactors to disconnect, and the inverter stops working.

2. To ensure that the abnormal protection of the frequency conversion will not affect the normal production. In order to prevent the non-sine wave from interfering with the air compressor controller, there are effective measures to suppress electromagnetic interference at the input end of the frequency converter. Shielded cables are used for control lines and signal lines, which are separated from power cables during wiring to prevent interference.

3. Keep the outlet pressure of the gas storage tank stable when the motor is running with frequency conversion, and the pressure fluctuation range should not exceed 0.02 MPa.

4. The air compressor is not allowed to run at low frequency for a long time. The speed of the air compressor is too low. The lower limit is not lower than 30 Hz.

6. Set high voltage protection, high temperature protection, etc. to set alarm and fault self-diagnosis.
(1) High pressure protection When the system pressure exceeds the set value, it will automatically cut off the power supply of the main engine to make the compressor stop in an emergency.
(2) High temperature protection When the exhaust temperature of the compressor exceeds the set value, the temperature sensor probe connected to the exhaust port of the main engine controls the action of the temperature electric contact, automatically cuts off the power supply of the motor, and makes the compressor stop in an emergency.
(3) The electrical protection system adopts the soft start mode, and has functions such as phase sequence protection (to prevent the compressor from reversing), phase loss protection, and motor thermal overload protection.

Advantages of air compressor after frequency conversion transformation

1. Energy saving: the overall energy saving is more than 20%.

(1) Energy saving during loading: After the air compressor is converted to frequency conversion, the pressure is always maintained at the required set working pressure, which can be reduced by 10% compared with before the modification. According to the power consumption formula, it can save energy by 10% after the modification. %.
(2) Energy saving during unloading. The energy consumed by the motor during unloading operation is about 40% of that during loading and unloading. Calculated according to the average unloading time of about a quarter, this item can save about 10% of energy.

2. The starting current is small and has no impact on the power grid.

The frequency converter can make the current rise smoothly when the motor is started and loaded without any impact; it can make the motor realize soft stop, avoid the harm caused by the reverse current, and help to prolong the service life of the equipment.

3. Stable output pressure

After the frequency conversion control system is adopted, the pressure of the gas in the gas supply pipeline can be monitored in real time, so that the pressure of the gas in the gas supply pipeline can be kept constant, and the production efficiency and product quality can be improved.

4. Less equipment maintenance

The frequency conversion air compressor has a small starting current, which is less than 2 times the rated current. The loading and unloading valve does not need to be repeatedly operated. The frequency conversion air compressor automatically adjusts the motor speed according to the air consumption. The operating frequency is low, the speed is slow, the bearing wear is small, and the service life of the equipment is extended. The workload becomes smaller.

5. Low noise

The frequency conversion provides energy according to the needs of gas consumption, without too much energy loss, the motor running frequency is low, and the mechanical rotation noise is therefore reduced. Due to the frequency conversion to adjust the motor speed, there is no need to repeatedly load and unload, and the noise of frequent loading and unloading is also gone. , continue to pressurize, and the noise caused by unstable air pressure also disappears. In short, after adopting the frequency conversion constant pressure control system, not only can save a considerable amount of electricity costs, prolong the service life of the compressor, but also achieve the purpose of constant pressure gas supply, improve production efficiency and product quality.

Sollant Group-Professional Compressed Gas Solutions Provider