7.5 KW 10 HP Variable Speed Drive Rotary Screw Air Compressor

As industrial screw air compressor manufacturer in China, we produce VFD/VSD compressor. And this is 7.5 KW 10 HPscrew air compressor for sale. Variable speed drive compressor has many advantages. One of the biggest advantages is energy saving.

What is vsd air compressor?

It’s also namely PM VSD screw air compressor. That is, permanent magnet variable frequency compressor. Firstly, it can change the rotational speed of the drive motor. Secondly, adjust the compressor airend speed. Finally, adjust the air discharge volume. Best screw compressor for sale!

Air capacity of vsd rotary screw compressor can be adjustable by itself. That is, change according to the customer’s on-site air consumption. Air demand changes the speed of the motor. Finally, it achieves the desired balance.

For example, the air consumption reaches the upper limit of the exhaust volume. At this time, the vsd compressor is running at full load.

On the contrary, the air consumption is less than the rated volume. At this time, the inverter reduces the frequency of the motor. Thereby reducing the airend speed accordingly. Eventually, it reduces the air discharge volume.

When stopping air usage, the variable frequency motor runs at low frequency. At the same time, the intake valve does not take in air. The screw compressor is in no-load state.

Technical parameters of 7.5 kw 10 HP PM VSD screw air compressor for sale

Why choose our variable frequency air compressor?

1. Firstly, use high efficiency screw airend

So the screw drive air compressor has the below advantages:

Adopt Sweden’s top SKF tapered roller bearings;
Reduce the exhaust pressure resistance;
Lower rpm, big air end and big discharge air volume;
Ensure high performance of vsd compressor;
At the same time, improve working efficiency of screw air compressor for sale;

2. Secondly, our air compressor uses permanent magnet variable frequency motor

It maintain very high motor efficiency at low speeds. Therefore, when the air consumption is small, it has obvious energy saving advantages.

Compared with fixed speed air compressor, the energy saving is 15%~38%. Compared to ordinary VSD air compressor, energy saving is 5%~10%. Moreover, the greater the fluctuation of air consumption, the more obvious the energy saving effect.

So our industrial air compressor machine has high overload capacity. Besides, has wider speed regulation range.

In addition, the permanent magnet motor uses NdFeB permanent magnets. So it will not lose magnetism at 120°C. The service life can be over 15 years.

3. Thirdly, use the smart control panel

Thus, it brings many advantages of our screw air compressor for sale.

Improve the ineractive experience of compressor operator;
Besides, support various mainstream PLC communication protocols;
And it can smoothly support animation and video playback;
In addition, faster data processing and response speed;

4. Finally, super filtration system

Use precise oil and air separation filter element;
So improve the compressed air separation efficiency;
Moreover, reduce the exhaust oil content;
At the same time, prevent pipeline blockage;

How does a vsd compressor work?

Firstly, the power frequency AC current is rectified into a stable DC current. Then convert it into AC current with adjustable frequency. Finally output to the variable frequency motor.

Inverter output frequency is proportional to the motor speed. Take a 4-pole motor as an example. When the output frequency is 20Hz, the motor speed is 600rpm. And when it is 50Hz, the motor speed is 1500rpm.

When the air consumption is large, the motor input frequency is high. So the speed is high. At this time, the air capacity of VSD compressor is high. On the contrary, when the air consumption is small, the input frequency of the motor is low. Thus, the rotation speed is low. And the air capacity of screw compressor for sale is small.

1. Control Logic of Fixed Speed Air Compressor

The fixed speed air compressor is set with two pressures. One is the loading pressure. Another is unloading pressure. Besides, its control is also very simple.

That is, the air pressure is less than the loading pressure. At this time, the screw air compressor is loading. Conversely, the air pressure is greater than the unloading pressure. At this time, the rotary air compressor is unloading.

During the unloading process, 25-50% of the power is consuming electricity. Therefore, it wastes a certain amount of energy.

As seen from the above figure, the air consumption of the power frequency air compressor has been fluctuating. The air pressure also fluctuates frequently.

So it is very likely that the loading pressure and the unloading pressure are set incorrectly. At this time, air fluctuations may damage our equipments. Moreover, frequent current fluctuations are also harmful.

2. Control principle of vsd variable frequency air compressor

In contrast, the vfd screw compressor for sale uses a PID controller. It sets a constant pressure. Firstly, it calculate through the proportional-integral-derivative. So it ensures the process of pressure increasing becomes smoothly.

Motor rotational speed has a quadratic relationship with the actual air consumption of vsd compressor. Therefore, in order to reduce the actual consumption, we can reduce the motor speed.

The inverter can control the motor speed in real time. That is, the output power. Then it will change the compressor speed. So it can respond instantly to pressure changes. And can maintain stable system pressure. Finally, it can achieve on-demand output of high-quality compressed air.

Why variable frequency air compressors saves energy?

Energy saving is the biggest advantage of vsd screw air compressor for sale.

Usually we choose compressor air capacity according to Max actual conditions. However, the actual air consumption only reach 60%-80% of the maximum rated value. Even it is lower.

The fixed speed air compressor adopts the loading and unloading control technology. When the air consumption is not large, we can do unloading operattion. So it can avoid compressor stop.

At this time, the motor idling. Thus, it will not generate compressed air. The power consumed at this time is called “unloading power”. In fact, it is a waste of energy.

But vsd air compressor is different. When the air consumption decreases, it will automatically reduce the speed. Thereby reducing power consumption. So there is no unloading loss. This is a big advantage of vfd screw air compressor for sale.

Of course, vsd compressor is not energy efficient under all conditions. As shown in the figure above, when running at full load, the energy saving effect is not so obvious.

If the air consumption is very stable, it is more appropriate to choose a fixed speed air compressor. Therefore, we need proper selection.

Specific case analysis of vsd screw air compressor for sale:

The company has 3 sets screw compressors. Among them, 2 units are 10m³/min (75kW). Now the production scale is expanded. Therefore, the air consumption is increasing significantly.

In order to ensure the safety of air use, add an vsd air compressor. It is 18.7m³/min, 1.23MPa and150kW.

We will use these three air compressors alternately. Swap every two weeks. 300 days of work per year. Also, work 14 hours a day.

The max discharge pressure of the vfd compressor is 1.1MPa. The actual air pressure is 0.6MPa. And the air pressure range is 0.4MPa-0.7MPa.

Observe the working conditions of two 10m³/min compressors. So we can obtain the following budget results :

After uses vsd, the compressor works for one hour. It can save 14~16 degrees of electricity. So the power saving rate is not less than 20%.

2# compressor works for one hour. Power saving is 12~14 degrees. So power saving rate is not less than 19%.

The two compressors work 14 hours a day. So total saving electricity is: (12+14)14=364 (kWh).  Assume that the work 150 days per year. Then the annual electricity saving is about 364150=54600 (kWh).

The current electricity fee is 0.85 CNY/kWh. Therefore, the annual electricity bill can be saved by 54600*0.85=46410 CNY.

Therefore, each vsd screw air compressor for sale can save over 23,000 CNY per year.

VSD air compressor use manual 1. How to install the screw air compressor for sale

Whether the installation is standard is very critical. Because it directly affects the performance of our vsd air compressor. So please refer to our user manual.

(1) Installation environment layout requirements

① Firstly, the compressor room should be as close to the load center as possible. In order to shorten the length of the pipeline. Moreover, it can reduce the pressure loss. And ensure the air supply pressure.

② Secondly, consider the rationality of power supply and water supply.

③ The vsd air compressor directly inhales the atmosphere. So it should be kept away from harmful substances and gases. For example, explosive, corrosive, toxic gas, dust, etc. This can our screw air compressor for sale.

④ In addition, the heat dissipation of VFD compressor is large. Especially in summer, the temperature inside is very high. Therefore, the room must be well ventilated.

⑤ Although the compressor has a shell, it is strictly forbidden to shower with rainwater. So should not install the industrial compressor outdoor.

(2) Screw drive compressor installation steps

① Firstly, install the outlet pipe of the variable frequency screw air compressor. As well as installing ball valves, adapters and connecting pipes.

② Secondly, configure the inlet connection of the air storage tank. And connect the pipeline from screw air compressor for sale.

③ Thirdly, install the tank pressure gauge. Then, install the safety valve. In addition, install a drain valve at the bottom of the air tank. Finally configure the auto drain.

④ Fourthly, install compressed air filter and pipes. Sometimes, the size of the filter is different from that of the air compressor and dryer. So we need to use some fittings.

⑤ Fifthly, install the automatic drainer at the bottom of the filter. In addition, install a ball valve after outlet of the filter. It is convenient to cut off the air. And facilitate the maintenance of refrigerated air dryer.

2. How to operate the variable frequency compressor

1. Firstly, complete the installation of vsd air compressor. At this time, the panel will display position and other control buttons. For example, switch emergency stop and set button.

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3. In principle, we can operate all switches on the panel. But there are always emergencies. Need to stop immediately. Otherwise, it will cause a safety accident. Therefore, each screw air compressor has an emergency stop button.

4. Make sure that each air compressor rotates correctly. However, when starting for the first time, pay attention to the forward and reverse rotation of the motor.

Press the start button first. Then press the emergency stop immediately. Another person observes if the motor rotation is correct. If reverse rotation, it needs to change phase.

4. Before starting vsd air compressor, check the valve at the exhaust port. Make sure it is always open. Otherwise compressor pressure cannot be released. Finally it will cause the safety valve above the tank to trip. Thereby, it will bring out internal screw oil.

   
   

5. Open the door. Check whether there is running, leaking or dripping inside. If there is, please contact for repairing.

Maintenance of screw compressor for sale

Failure to maintain will cause great harm to the air compressor. Correct maintenance plays a vital role in the service life of the vsd air compressor. So keep it on time.

(1) Daily Maintenance

① During startup, check whether the oil level is in the green area;
② Operate the drain valve of the air storage tank once a day;
③ Operating range of VSD compressor is always in the loading and unloading pressure section;

(2) Maintenance every three months

① Clean the compressor air filter element. Also clean the automatic trap;
② Clean the air inlet of the motor. Also clean water cooling water inlet filter;
③ Check whether there is any abnormal sound during the operation of the screw air compressor for sale;
④ Check the tightness and safety grounding in the electric control cabinet;

(3) Maintenance every 4000 hours

① Check the electrical connection;
② Cooling water system:
A) Clean the scale and dirt in the cooling water tank. Also clean the dirt in the filter at the inlet of the pump;
B) Check for dirt in the cooling tower. Also check fan rotation.
③ Verify the sensitivity of the tank pressure gauge and safety valve.

(4)Maintenance every 8000 hours

① Replace the third filter of vsd air compressor. Namely air filter element, oil filter and oil separator element;
② Test and verify the safety valve.

Troubleshooting of vsd screw compressor

There are various reasons for the failure of vfd compressor. Blow are common malfunctions of screw air compressor for sale. At the same time, also give the solutions. But it is impossible to list all faults and troubleshooting methods.

(1) Unable to start

① Firstly, maybe the power is not on —— so close the switch to turn on the power.

② Secondly, the control circuit fuse maybe blown —— then replace the fuse.

③ Thirdly, the discharge temperature is too high. So cause vsd compressor shutdown —— solve the high temperature problem first. Then restart screw air compressor for sale.

④ The thermal overload relay is disconnected —— correct the cause of the overload. Reset the thermal overload appliance.

⑤ The voltage may also be too low —— ask the power department to check the input voltage. And compare with the motor terminal voltage. So as to check the cause of the low voltage.

⑥ Power failure —— check the power supply.
⑦ Loose wiring —— check all wiring terminals. And fasten it.
⑧ Compressor temperature sensor failure —— overhaul the sensor.

(2) Thermal overload relay open

① VSD compressor discharge pressure is too high —— so set the unloading pressure lower.

② Or the voltage is too low —— check the input voltage and current at full load.

③ The thermal overload relay wiring is loose —— so need to tighten wiring screws.

④ Setting is incorrect – check the motor nameplate first. Then compare it with the overload relay setting.

⑤ Motor or starter wiring is loose —— check whether all wiring is tightened.

⑥ It may also be the fault of the air compressor motor —— overhaul the motor, or replace it.

(3) Excessive consumption of lubricating oil

① The oil level in the oil-air separator is too high —— firstly, exhaust part of the lubricating oil. Lower the oil level to the specified height. Observe the oil level gauge while vsd air compressor is running. Determine the oil level.

② The secondary oil return line is blocked —— clean the oil return line. Also, check to see if the check valve is damaged.

③ The exhaust temperature of screw compressor is too high —— refer to the following specific solutions.

④ Damaged oil separator element—— replace the air-oil separator of screw air compressor for sale.

⑥ Lubricating oil pipeline leakage —— check for leakage. Then replace the seal.

⑦ Loading and unloading cycles are too frequent —— overhaul;

⑨ Improper use of lubricating oil—— use the recommended lubricating oil.

(4) Too high discharge temperature

① The amount of cooling water in the cooler is insufficient (only for water-cooled screw air compressor for sale) —— clean the cooler. Check for water system failures.

② Insufficient air circulation in the cooler —— Check the installation position of the cooler. Make sure the airflow is not obstructed. Clean as necessary.

③ The oil level in the oil-air separator is too low —— add oil to the recommended height. Check the oil system for leakage.

④ The oil filter is blocked —— replace the oil filter element of vsd compressor.

⑤ The oil cooler is blocked —— check whether there is rust. Thoroughly clean the compressor cooler.

⑥ The ambient temperature is too high —— it should not exceed the max rated temperature of screw compressor.

⑦ Wrong direction of fan rotation —— the correct direction is that the fan pushes air into the cooler. So swap any two of the three-phase power lines.

⑧ Incorrect lubricating oil —— we are using Shell brand oil.

⑨ Compressor air filter clogged —— Clean or replace the air filter.

⑩ The temperature control valve is damaged——repair or replace as necessary.

⑪ The compressor airend is damaged —— contact our after-sales service department.

(5) Insufficient air supply of screw compressor for sale

① Air filter clogged —— clean or replace the air filter of vsd compressor. If the environment is harsh, please install a pre-filter.

② There is leakage in the pipeline —— you can check the leakage of the pipeline with soapy water.

③ The intake valve is not fully opened —— check whether the solenoid valve, discharge valve and servo cylinder are working normally.

FAQ

1. Why has my screw compressor stopped working?

The following reasons may cause vsd air compressor to stop suddenly.
Firstly, the exhaust temperature of the screw air compressor for sale is high.
Secondly, the unloading valve is faulty.
Thirdly, the airend resistance is too large.
In addition, the thermal relay circuit is short-circuited or has poor contact.

2. How often should compressors be serviced?

For a new vsd air compressor, it is necessary to carry out routine maintenance after use for sometime. Maintenance is divided into small and major maintenance.

For the former, it only needs to replace the air compressor oil and oil filter. Generally, it is replaced when the new compressor runs for 500 hours.

For the latter, also needs to replace the air filter and the oil-air separator element. Also replace the motor grease etc. Usually carry out this maintenance when compressor is running for about 3000 hours.

Of course it depends on the work environment. If it’s very dirty, should reduce time appropriately.

3. Difference between single screw and twin screw compressor

They have multiple differences.

① Manufacturing cost different

Single screw air compressors can withstand ordinary bearings. Therefore, the cost is low.

However, the latter uses two screws. Because of the large load on the rotor and the high precision, the cost is high.

② Different applicability

Single screw air compressor: suitable for occasions with high exhaust pressure.

The two screw air compressor for sale: It can only be suitable in the medium and low pressure range. Because there are constraints such as rotor stiffness and bearing compliance.