Variable speed rotary screw compressor

LU 7.5–90 PMi

The Liutech LU 7.5-90 PMi range combines permanent magnet motor technology with intelligent variable speed control to deliver efficient compressed air from 7.5 to 90 kW. Designed for a wide range of industrial applications, these compressors adapt to changing air demand while supporting stable pressure and reliable operation.

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LU 45 PMI Screw Air Compressor front view

High efficient PM drive

Oil‑cooled IE4/IE5‑class permanent‑magnet motors deliver high torque at low speed, eliminate fan maintenance and provide excellent long‑term efficiency in continuous operation.

Precise control

A high‑precision vector inverter and AIRLOGIC² T controller maintain tight pressure stability and continuously optimise motor speed to match real air demand.

Robust cooling

Separated oil and air cooling zones with enlarged cooling surfaces protect electronics and motor components, ensuring reliable operation in high ambient temperatures up to 46℃.

7.5–90 kW Permanent magnet variable speed compressors for industrial use

The LU 7.5–90 PMI  series uses high efficiency in-house designed screw element  to reduce internal leakage and improve free air delivery, especially during low‑speed operation. Its oil‑cooled permanent‑magnet motor, built with high‑temperature‑resistant magnets, maintains efficiency over time while eliminating fan‑related maintenance. Direct coupling removes transmission losses and enhances mechanical stability during continuous duty.

To adapt precisely to changing air demand, a high‑precision vector inverter enables wide turndown while maintaining a tight pressure band through regulation. The intelligent controller provides clear system status, alarms and service reminders. Together with separated cooling zones and optimised thermal routing, the LU PMI range delivers robust operation, strong electronic protection and dependable performance in elevated ambient conditions.

LU 7.5–90 PMI Screw Air Compressor inside view

Across the 7.5–90 kW range, LU PMI compressors operate at typical industrial pressures from around 7 to 10.5 bar, with wide flow ranges tailored to each power size. Performance is tested according to ISO 1217 reference conditions to ensure accurate free air delivery values and consistent comparison across models.

Reinforced frames, efficient thermal separation and high‑capacity cooling support reliable operation in ambient temperatures up to about 46 °C while maintaining stable discharge temperatures and pressure profiles.

Maintenance is simplified by the direct‑drive design. The oil‑cooled permanent‑magnet motor requires no re‑greasing or fan cleaning, and externally accessible filters and separation components allow fast, predictable routine service.

The intelligent controller supports maintenance planning with service reminders and diagnostic information. This combination helps identify issues early, reduce unplanned downtime and support long‑term reliability throughout the compressor’s operating life.

Permanent‑magnet variable‑speed technology allows motor speed to closely follow real‑time air demand, reducing energy consumption by up to around 35% compared with fixed‑speed compressors in variable‑load applications. Stable pressure control further reduces unload time and leakage‑related energy losses.

Reliable components, effective cooling and reduced mechanical stress extend service intervals and lower total operating cost. Integrated monitoring improves planning and uptime, while consistent airflow quality enhances downstream equipment efficiency, making the LU 7.5–90 PMI range a cost‑effective long‑term industrial solution.

Technical information

Model Pressure Motor Capacity Weight Connection Dimension
Bar(g) kW l/s cfm Kg G LxWxH (mm)
LU7.5 PMI 7-8.5 7.5 8.2-21 17-44 195 G3/4'' 914x850x1050
10-10.5 7.2-18 15-39
LU11 PMI 7-8.5 11 9.1-32 19-68 195 G3/4'' 914x850x1050
10-10.5 7.2-27 15-57
LU15 PMI 7-8.5 15 11.8-42 25-88 215 G1'' 1014x850x1200
10-10.5 11.5-35 24-74
LU18.5 PMI 7-8.5 18.5 14.7-54 31-117 245 G1'' 1014x850x1200
10-10.5 12.5-45 26-95
LU22 PMI 7-8.5 22 19.3-69 41-145 335 G1 1/2'' 1178x1050x1350
10-10.5 18-57 38-120
LU30 PMI 7-8.5 30 27.3-95 58-201 370 G1 1/2'' 1178x1050x1350
10-10.5 24.2-80 51-170
LU37 PMI 7-8.5 37 37.8-116 80-247 495 G1 1/2'' 1264x1197x1500
10-10.5 34.6-93 73-198
LU45 PMI 7-8.5 45 41.5-142 88-300 530 G1 1/2'' 1264x1197x1500
10-10.5 43-113 91-240
LU55 PMI 7-8.5 55 45-183 95-388 840 G2'' 1656x1089x1840
10-10.5 40-157 85-332
LU75 PMI 7-8.5 75 53-217 113-459 865 G2'' 1656x1089x1840
10-10.5 43-187 92-396
LU90 PM 7-8.5 90 88-290 187-614 1520 G2'' 1806x1089x1840
10-10.5 77-242 162-512
LU7.5 PMI TMDD 7-8.5 7.5 8.2-21 17-44 598 G3/4'' 1887x900x1862
10-10.5 7.2-18 15-39
LU11 PMI TMDD 7-8.5 11 9.1-32 19-68 598 G3/4'' 1887x900x1862
10-10.5 7.2-27 15-57
LU15 PMI TMDD 7-8.5 15 11.8-42 25-88 626 G1'' 1887x900x2012
10-10.5 11.5-35 24-74
LU18.5 PMI TMDD 7-8.5 18.5 14.7-54 31-117 788 G1 1/2'' 2057x1050x2162
10-10.5 12.5-45 26-95
LU22 PMI TMDD 7-8.5 22 19.3-69 41-145 788 G1 1/2'' 2057x1050x2162
10-10.5 18-57 38-120

Unit performance measured according to ISO 1217, Annex C, ed.4 2009.

LU 7.5-90 PMI

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