Description
The Atlas Copco ZR 90 VSD is the 90 kW model of the oil-free rotary screw range, built around two-stage compression and variable speed drive. It closes the top of the ZR/ZT 55-90 platform at 90 kW / 120 hp, and the family spans the VSD, VSD+ and VSD FF versions in 50 Hz and 60 Hz, all carrying the ISO 8573-1 Class 0 certification that oil-free applications demand.
Where the ZR 90 VSD Sits in the Oil-Free Range
The oil-free screw range below 100 kW is organized around the ZR/ZT 55-90 platform. ZR 55 and ZR 75 cover the lower power bands with installed motor ratings of 55/75 and 75/100 kW/HP, and the ZR 90 closes the platform at 90 kW / 120 hp. The letter ZR marks the water-cooled package, while the ZT 90 is the air-cooled counterpart built around the same two-stage oil-free element. Both letters share the platform’s technical data.
The VSD+ generation carries the same model into the newer ZR 90-160 platform. In that generation the package reaches 70 dB(A) at the work station, and the weight structure separates into Pack, Full Feature (iMD) and Full Feature (iMDG) branches.
VSD, VSD+ and VSD FF: What Each Name Means
Three names describe the versions, and each name adds one fact:
- VSD — variable speed drive: the main motor follows air demand through the drive, which holds the pressure band steady and trims energy use at part load.
- VSD+ — the newer generation of the same concept, built on the ZR 90-160 platform with lower sound levels and updated electronics.
- VSD FF — Full Feature: the package includes an integrated heat-of-compression MD dryer, marked iMD or iMDG in the VSD+ generation, so drying happens inside the package rather than beside it.
Both 50 Hz and 60 Hz versions exist across the family.
Performance Data of the ZR 90 VSD
The tested package performance of the ZR 90 VSD is recorded at four rated pressures, measured according to ISO 1217, Annex E. The tested models ZR 90VSD-125 and ZR 90VSD-150 are two-stage oil-free screw packages with a 121 hp drive motor at 93.5 percent nominal efficiency.
| Rated pressure | Max capacity | Specific power | Package input power | No-load power |
|---|---|---|---|---|
| 100 psig | 548 acfm | 21.0 kW/100 acfm | 114.9 kW | 10.2 kW |
| 125 psig | 509 acfm | 22.5 kW/100 acfm | 114.4 kW | 10.2 kW |
| 130 psig | 501 acfm | 22.9 kW/100 acfm | 114.6 kW | 12.4 kW |
| 150 psig | 469 acfm | 24.3 kW/100 acfm | 114.1 kW | 12.4 kW |
Reading the Pressure and Capacity Trade-Off
Capacity falls from 548 acfm at 100 psig to 469 acfm at 150 psig as the same two-stage element compresses to a higher pressure, while specific power rises from 21.0 to 24.3 kW per 100 acfm. Package input power stays between 114.1 and 114.9 kW across all four points, which is the VSD drive holding the motor near its efficient operating range.
No-load power separates the two gearbox versions. The ZR 90VSD-125 draws 10.2 kW at zero flow, and the ZR 90VSD-150 draws 12.4 kW, a difference that matters in plants with long unloaded periods.
The part-load points on the 100 psig sheet add the turndown story: specific power holds 20.6-20.7 kW/100 acfm down to 353 acfm, rises to 21.7 at 256 acfm, and reaches 24.9 at the 158 acfm floor. The ZR 90 VSD keeps its best specific power through the mid-load band where most plants operate.
Technical Specifications of the ZR 90 VSD
The table below condenses the family into its headline figures. Where the branches differ, the figures reflect the largest Full Feature configuration of the VSD+ generation, and the section that follows breaks the branches out separately.
| Parameter | Value |
|---|---|
| Model | Atlas Copco ZR 90 VSD |
| Compressor type | Oil-free two-stage rotary screw |
| Capacity control | Variable speed drive (VSD) |
| Installed motor power | 90 kW / 120 hp |
| Drive motor | 121 hp at 93.5 percent nominal efficiency |
| Frequency | 50 Hz and 60 Hz |
| Working pressure | 4-10.4 bar(e) / 58-150 psig by version |
| Free air delivery | Up to 298 l/s (17.9 m³/min / 631 cfm) |
| Sound level | From 70 dB(A) at the work station |
| Weight, largest branch | 3,700 kg / 8,200 lb |
| Dimensions (L × W × H), largest branch | 3,430 × 1,660 × 2,000 mm (135 × 65 × 80 in) |
| Air quality | ISO 8573-1 Class 0, TÜV certified |
Rated Data of the ZR 90 VSD – 8.6 and ZR 90 VSD – 10.4
The two pressure versions of the ZR 90 VSD share the same 90 kW / 120 hp motor, and the 50 Hz data lists each of them at three pressure settings. The FAD span inside every row covers the full VSD speed range at that setting:
| Model | Setting | Working pressure | FAD (l/s) | FAD (m³/min) | FAD (cfm) | Noise |
|---|---|---|---|---|---|---|
| ZR 90 VSD – 8.6 | Minimum | 6 bar(e) / 58 psig | 75.1-297.2 | 4.51-17.8 | 159.1-629.7 | 71 dB(A) |
| ZR 90 VSD – 8.6 | Effective | 7 bar(e) / 100 psig | 74.1-282.5 | 4.4-16.9 | 157-598.6 | 71 dB(A) |
| ZR 90 VSD – 8.6 | Maximum | 8.6 bar(e) / 125 psig | 73.6-258.1 | 4.42-15.5 | 155.9-546.9 | 71 dB(A) |
| ZR 90 VSD – 10.4 | Minimum | 6 bar(e) / 87 psig | 76.5-292.9 | 4.6-17.6 | 162.1-620.6 | 74 dB(A) |
| ZR 90 VSD – 10.4 | Effective | 9 bar(e) / 130 psig | 75.5-250.5 | 4.53-15 | 160-530.8 | 74 dB(A) |
| ZR 90 VSD – 10.4 | Maximum | 10.4 bar(e) / 150 psig | 75.0-229.2 | 4.5-13.7 | 158.9-485.6 | 74 dB(A) |
The 8.6 bar(e) version peaks at 297.2 l/s on its minimum setting, and the 10.4 bar(e) version peaks at 292.9 l/s. Within one version, the maximum pressure setting costs about 40 l/s of peak FAD against the minimum setting.
Rated Data of the ZR 90 VSD+ – 10.4
The VSD+ generation builds the model on the ZR 90-160 platform with the same 90 kW / 120 hp drive at 70 dB(A), listed at three pressure settings across the VSD+ speed range:
| Setting | Working pressure | FAD (l/s) | FAD (m³/min) | FAD (cfm) |
|---|---|---|---|---|
| Minimum | 4 bar(e) / 60 psig | 90-298 | 5.4-17.9 | 192-631 |
| Effective | 7.5 bar(e) / 100 psig | 90-276 | 5.4-16.5 | 192-584 |
| Maximum | 10.4 bar(e) / 150 psig | 90-231 | 5.4-13.9 | 188-490 |
The ZR 90 VSD+ – 10.4 holds the largest FAD figure in the family, 631 cfm at its minimum setting; its package weights appear in the branch table below.
Size and Weight Across the Family Branches
The weight and footprint of the ZR 90 VSD depend on the branch. The spread between the lightest and the heaviest configuration is more than a tonne and a half:
| Branch | Weight | Dimensions (L × W × H) |
|---|---|---|
| ZR 90 VSD, Standard | 1,970 kg / 4,343 lb | 2,180 × 1,450 × 2,184 mm |
| ZR 90 VSD, Full Feature | 2,220 kg / 4,894 lb | 2,180 × 1,450 × 2,184 mm |
| ZR 90 VSD+, Pack | 2,500 kg / 5,512 lb | 2,030 × 1,660 × 2,000 mm |
| ZR 90 VSD+, FF (iMD) | 3,400 kg / 7,400 lb | 3,430 × 1,660 × 2,000 mm |
| ZR 90 VSD+, FF (iMDG) | 3,700 kg / 8,200 lb | 3,430 × 1,660 × 2,000 mm |
The pattern in the table is easy to read. The integrated dryer adds length: the Full Feature packages of the VSD+ generation stretch to 3,430 mm against 2,030 mm for the Pack. On the earlier generation the Standard and Full Feature packages of the ZR 90 VSD share the same 2,180 mm footprint, so the dryer there adds weight but not floor space. Sound levels follow the same spread, from 70 dB(A) on the VSD+ package up to 74 dB(A) on the highest-pressure settings of the earlier generation.
Two-Stage Oil-Free Compression Inside
Compression runs through two stages, and each stage works on its own pair of oil-free rotors. Air enters the first-stage air end after filtration, leaves it at an intermediate pressure, and passes the intercooler before the second stage raises it to the final level. The gears between motor and elements set the speed ratio for each stage, and the whole train sits inside one gear casing. This two-stage layout is what lets the ZR 90 VSD reach 10.4 bar(e) without pushing a single stage past its design pressure.
- Filtration and first compression — ambient air enters the first-stage air end and is compressed to an intermediate pressure.
- Cooling and second compression — the intercooler lowers the temperature before the second stage brings the air to its final pressure.
- Cooling and drying — the after-cooler condenses moisture out of the air, and on Full Feature packages the heat-of-compression MD dryer regenerates with compression heat.
The oil circuit stays outside this path. A pump feeds cool, filtered oil to the bearings and the gears and returns it to the sump, so the compressed air never meets lubricant at any stage. That separation is the mechanical basis of the Class 0 certificate, and it is the reason the ZR 90 VSD appears in air systems where oil carry-over would stop production.
Air Quality and Applications
ISO 8573-1 Class 0 is the strictest air purity class in the standard, and Atlas Copco was the first compressor manufacturer to receive the certification, with TÜV as the certifying body. The ZR 90 VSD carries that certification on the compressed air at the outlet flange. For buyers, the certificate removes the need to interpret oil aerosol numbers against class limits, because the limit itself is zero.
The applications follow directly. Electronics manufacturing, food and beverage, pharmaceutical production, chemical processing and textile plants all specify oil-free air either by regulation or by product sensitivity, and these are the plants where the ZR 90 VSD is written into the specification. The pressure version narrows the choice: the 8.6 bar(e) version covers the general plant band up to 125 psig, while the 10.4 bar(e) version reaches 150 psig for higher-pressure processes.
Service and Support Around the ZR 90 VSD
The Elektronikon controller monitors the package, adapts the drive to the demand profile and records the data service teams use at inspection time. The two-stage element, the drive train and the integrated dryer of the FF branches all sit inside Atlas Copco’s documented service structure, with service kits and spare parts defined for the platform.
The -125 and -150 suffixes on the tested models point to the gearbox version behind the pressure rating. A photograph of the machine plate together with the compressor model is enough to fix the version before any parts conversation starts.
Seadweer supplies genuine Atlas Copco spare parts and service kits for the installed base of the ZR 90 VSD. Send us the compressor model and serial number together with the parts you need, and the correct items are confirmed with the quotation in one pass.
FAQ
What does VSD mean on the Atlas Copco ZR 90 VSD?
VSD stands for variable speed drive. The drive adjusts the main motor speed to the air demand, so the package holds the pressure band and avoids unloaded running at part load.
How much air does the ZR 90 VSD deliver?
Peak free air delivery reaches 298 l/s, or 631 cfm, at the lowest working pressure setting. At 100 psig the package delivers 548 acfm, and at 150 psig the figure is 469 acfm.
What is the difference between the ZR 90 VSD and the ZT 90?
The letter marks the cooling type. The ZR 90 VSD is the water-cooled package, and the ZT 90 is the air-cooled counterpart built on the same two-stage oil-free platform.
What is the difference between VSD and VSD+?
VSD+ is the newer generation of the same variable speed concept, built on the ZR 90-160 platform. It brings a 70 dB(A) package rating and the iMD and iMDG Full Feature branches.
What does VSD FF add to the ZR 90 VSD?
FF stands for Full Feature: an integrated heat-of-compression MD dryer inside the package. In the VSD+ generation these branches are marked iMD and iMDG, and they add weight and length to the package.
Is the ZR 90 VSD certified for ISO 8573-1 Class 0?
Yes. The oil-free range carries ISO 8573-1 Class 0 (2010) certification with TÜV as the certifying body, so the air at the outlet is covered by certified measurement at the strictest class.
Ahmed Al-Rashid –
We replaced an ageing oil-free unit with the ZR 90 VSD after comparing the rated figures for the 100 psig setting, and the installed machine has matched them. The VSD drive keeps the pressure band steady through shift changes, and the Elektronikon readings show exactly where the energy goes. Seadweer answered our configuration questions before the order and followed up with the service plan for the new package.