Description
CM/DV Series Low Pressure Permanent Magnet Variable Frequency Oil-Free Screw Air Compressor
The CM/DV series combines oil-free screw compression with a permanent magnet variable frequency drive motor, producing a low-pressure compressor that adjusts its output speed in real time to match actual plant air demand. For operations where compressed air requirements vary across shifts, seasons, or production cycles, this variable-speed capability can meaningfully reduce energy consumption compared to fixed-speed compressors running at full load regardless of actual draw.
The series covers motor power from 45 kW to 160 kW and working pressures from 0.12 MPa to 0.40 MPa (17–58 psi). Free air delivery ranges from 5.50 m³/min at minimum speed on the CM45DV up to 42.88 m³/min at full speed on the CM160DV, giving each model a turndown capability that a fixed-speed unit cannot match. Discharge air temperature is held at 45 °C or below, and because the compression stage is oil-free, the delivered air contains no oil carryover.
For facilities that have already evaluated fixed-speed options, the CM/DV is worth comparing when the daily load profile shows significant variation, when energy cost reduction is a priority, or when the application requires oil-free air quality alongside efficient part-load operation. The full comparison of available types is covered in the medium and low pressure air compressor range.
Key Technical Features
Permanent Magnet Variable Frequency Drive Motor
The CM/DV uses a permanent magnet (PM) synchronous motor driven by an integrated variable frequency drive (VFD). PM motors maintain high efficiency across a wide speed range, unlike standard induction motors that lose efficiency significantly at partial load. Combined with the VFD, the compressor speed tracks actual demand, reducing power consumption during periods of lower air use. This is the primary distinction between the CM/DV and the fixed-speed CM/D series.
Variable FAD Output — Matched to Demand
Each CM/DV model covers a speed-dependent FAD range rather than a fixed output point. The CM45DV, for example, delivers between 5.50 and 13.80 m³/min depending on compressor speed, while the CM160DV ranges from 17.10 to 42.88 m³/min. This turndown range means the compressor can serve both low-demand periods and peak-demand periods from the same unit, without the pressure fluctuation and start-stop cycling that fixed-speed units produce at partial load.
Certified Oil-Free Compressed Air
The screw air-end operates without oil in the compression chamber. There is no oil injection, no oil separator, and no oil carryover into the delivered airstream. For applications in food processing, pharmaceuticals, electronics manufacturing, or any process where oil contamination is unacceptable, the CM/DV meets the air purity requirement at the source without relying on downstream filtration to compensate.
Stable Discharge Pressure with Narrow Band Variation
Because the VFD adjusts motor speed rather than loading and unloading a fixed-speed compressor, the supply pressure stays within a tighter band around the setpoint. Fixed-speed compressors typically cycle between a lower cut-in pressure and an upper cut-out pressure, creating a pressure swing that pneumatic equipment must be designed to accommodate. Variable speed operation reduces this swing, which can improve the performance consistency of pressure-sensitive downstream processes.
Water-Cooled Design for Consistent Performance
Like the fixed-speed CM/D series, the CM/DV uses water cooling throughout. This keeps discharge temperature at or below 45 °C independent of ambient conditions and supports sustained full-load operation in high-temperature plant environments. Cooling water connections are DN40 for the CM45DV through CM75DV, and DN80 for the CM110DV through CM160DV, with flow requirements ranging from 12 T/h to 35 T/h referenced at 32 °C inlet temperature.
Reduced Mechanical Stress and Lower Noise at Partial Load
Variable speed operation reduces the mechanical stress cycles that fixed-speed loading and unloading imposes on the drive train and air-end. At partial load, the compressor runs more quietly than at full speed — a practical benefit in facilities where compressor room acoustics are a consideration. The CM45DV and CM55DV operate at 70 dB(A) at rated load, with actual noise lower during part-load operation.
Technical Specifications — CM/DV Series (Variable Frequency)
Water-cooled | Supply gas temperature ≤45 °C | Cooling water inlet temperature reference: 32 °C | FAD range reflects variable speed output
| Model | Work Pressure MPa / Psi |
FAD Range m³/min / cfm |
Motor Power kW / HP |
Noise dB(A) |
Weight kg |
Cooling Water Pipe Inlet/Outlet |
Cooling Water Qty T/h (32 °C) |
Dimensions L×W×H mm |
Air Outlet |
| CM45DV | 0.12–0.25 / 17–36 | 5.50–13.80 / 194–487 | 45 / 60 | 70 | 1720 | DN40 | 12 | 2200×1350×1530 | DN65 |
| CM55DV | 0.25–0.40 / 36–58 | 5.40–13.60 / 191–480 | 55 / 75 | 70 | 1750 | DN40 | 18 | 2200×1350×1530 | DN65 |
| CM75DV | 0.25–0.40 / 36–58 | 8.04–20.10 / 284–710 | 75 / 100 | 72 | 2300 | DN40 | 20 | 2200×1350×1530 | DN65 |
| CM110DV | 0.25–0.40 / 36–58 | 12.00–30.10 / 424–1063 | 110 / 150 | 78 | 3790 | DN80 | 24 | 3100×1700×2090 | DN125 |
| CM132DV | 0.12–0.25 / 17–36 | 17.20–43.00 / 607–1518 | 132 / 180 | 78 | 3850 | DN80 | 30 | 3100×1700×2090 | DN125 |
| CM160DV | 0.25–0.40 / 36–58 | 17.10–42.88 / 604–1514 | 160 / 220 | 78 | 3900 | DN80 | 35 | 3100×1700×2090 | DN125 |
FAD range reflects variable speed output from minimum to maximum compressor speed. Actual operating range depends on setpoint pressure and speed limits.
How to Select the Right CM/DV Model
The selection process for a variable frequency model has one additional consideration compared to a fixed-speed unit: you need to account for both peak demand and average demand, not just peak.
Size for peak, evaluate at average. The compressor must be capable of meeting your maximum instantaneous demand at full speed. Use the upper FAD figure for each model to confirm it covers your peak requirement. Then assess whether your average daily load — the actual airflow consumed over a shift or a day — is significantly below that peak. If average load is 60–70% or less of peak capacity, a variable frequency drive is likely to produce meaningful energy savings over a fixed-speed alternative running at full output.
Pressure range selection. The CM45DV and CM132DV cover the lower pressure band of 0.12–0.25 MPa (17–36 psi). The CM55DV, CM75DV, CM110DV, and CM160DV operate at 0.25–0.40 MPa (36–58 psi). Match the model’s rated pressure range to your process requirement before evaluating FAD.
Cooling water requirements. The CM/DV is water-cooled and requires the same cooling water supply as the fixed-speed CM/D equivalent. Confirm that your facility’s cooling water system can support the required flow rate for your selected model before installation planning proceeds.
CM/DV versus CM/D: when does VFD pay off? Variable frequency drives add capital cost. The payback period depends on local energy costs, daily operating hours, and how variable your demand profile actually is. For operations running at consistent near-full load for most of the day, the CM/D fixed-speed series may be more cost-effective. For operations with significant partial-load periods — overnight reduced production, batch processes with gaps between runs, seasonal variation — the CM/DV is typically the better long-term choice.
Typical Applications
The CM/DV is most beneficial in applications where both oil-free air quality and variable demand profiles apply simultaneously.
- Pharmaceutical Manufacturing — Fermentation, coating drums, and cleanroom pressurization require confirmed oil-free air. Batch-based production typically generates variable air demand, making the CM/DV’s part-load efficiency particularly useful.
- Food and Beverage Processing — Pneumatic conveying, packaging line actuation, and process air in food plants require oil-free compressed air. Variable production schedules — multiple product runs per shift, cleaning cycles between batches — create the demand variation where VFD saves energy.
- Electronics and Semiconductor Manufacturing — Cleanroom environments and component assembly lines use oil-free compressed air. Demand may vary with shift patterns and production mix, making variable speed operation practical.
- Wastewater Treatment — Biological aeration demand varies with influent load, time of day, and seasonal patterns. Oil-free air is required where the compressed air contacts the biological treatment process. The CM/DV can reduce aeration energy costs compared to fixed-speed operation by matching output to actual oxygen demand.
- Textile Manufacturing — Air-jet loom systems run oil-free air at 3–4 bar. Weaving operations often run multiple shifts with differing numbers of active looms, creating a demand profile that benefits from variable speed operation.
- Chemical Processing — Process gas, instrument air, and reaction vessel aeration in chemical plants often require oil-free air at controlled pressures. Batch chemical processes create the variable demand that makes VFD operation cost-effective.
- Industrial Automation — Centralized plant air for robotic systems and automated assembly lines may vary significantly between production runs, shift changes, and maintenance periods. Variable frequency operation avoids the inefficiency of a fixed-speed compressor unloading and reloading during these transitions.
Variable Frequency vs. Fixed Speed vs. Micro-Oil: Choosing Your Configuration
All three low-pressure screw compressor types are available within the CM/D product family. The table below summarizes the trade-offs for the three most relevant choices when evaluating the CM/DV.
| Type | Key Advantages | Best Suited For |
| Variable Frequency Oil-Free CM/DV Series |
Speed adjusts to match actual demand. Permanent magnet motor maintains efficiency at partial load. Narrower supply pressure band. Oil-free compression. Reduced mechanical cycling. | Applications requiring oil-free air with variable demand profiles. Facilities prioritizing long-term energy cost reduction. Batch processes, multi-shift operations with varying production volumes. |
| Fixed Speed Oil-Free CM/D Series |
Lower capital cost than VFD equivalent. Simpler drive system. Well-suited to continuous constant-load operation. Oil-free compression. Water-cooled for stable performance. | Applications requiring oil-free air at consistent near-full load. Operations running 24/7 at steady demand. Situations where capital cost is a higher priority than part-load efficiency. |
| Micro-Oil Screw Compressor CMN/D Series |
Lower capital cost. Air-cooled — no water supply required. Higher volumetric efficiency due to oil sealing. Broader power range from 22 kW. ≤2 PPM oil content. | General industrial applications where 2 PPM oil content is acceptable. Locations without cooling water infrastructure. Applications where air quality requirements allow micro-oil with downstream filtration. |
See the full medium and low pressure air compressor range for detailed specifications across all series.
Frequently Asked Questions
What is a permanent magnet variable frequency oil-free screw compressor?
It is a screw air compressor with three integrated characteristics: the compression stage runs without oil (oil-free), the motor is a permanent magnet synchronous type with higher part-load efficiency than standard induction motors, and the motor is driven by a variable frequency drive (VFD) that adjusts compressor speed to match actual air demand. The combination produces an oil-free compressor that uses less energy during partial-load operation than a fixed-speed equivalent, which is the main reason for specifying this configuration over the simpler CM/D series.
How much energy can a variable frequency compressor save?
Energy savings depend on your actual load profile. In applications where demand varies between 40% and 80% of rated capacity across a typical operating day, energy savings of 15–30% compared to a fixed-speed unit are commonly observed. If your compressor runs at consistent near-full load for the majority of its operating hours, the savings potential is lower, and the fixed-speed CM/D may offer better value. The case for a VFD is strongest when partial-load periods are frequent and extended.
What does the FAD range in the CM/DV specifications mean?
Free air delivery (FAD) is the actual volume of air the compressor delivers at rated conditions. For a fixed-speed compressor, this is a single figure. For the CM/DV variable frequency series, the FAD range reflects the output at minimum and maximum compressor speed. For example, the CM55DV delivers between 5.40 and 13.60 m³/min depending on how fast the motor is running, which in turn depends on how much air the system is drawing. The compressor adjusts speed continuously to maintain your setpoint pressure.
Is the CM/DV series suitable for continuous 24/7 operation?
Yes, the CM/DV is designed for continuous industrial operation. Variable frequency operation actually reduces the thermal and mechanical cycling that load-unload fixed-speed operation produces, which can benefit long-term reliability. The water-cooled design supports sustained full-load running independent of ambient temperature. For critical continuous operations, specifying a standby unit is standard practice regardless of compressor type.
What is the difference between the CM/DV and CM/D series?
Both series are oil-free, water-cooled low-pressure screw compressors covering the same power and pressure ranges. The CM/D is fixed-speed: it runs at rated output when operating. The CM/DV adds a permanent magnet motor and variable frequency drive that adjust compressor speed to match actual demand. The CM/DV costs more upfront but can reduce energy costs in variable-load applications. For constant-load operations, the CM/D is typically the more cost-effective choice.
What maintenance does the CM/DV require compared to fixed-speed models?
The CM/DV shares the same oil-free maintenance profile as the CM/D: no oil filters, oil separators, or oil sampling. Additional maintenance considerations specific to the VFD configuration include periodic inspection of the VFD unit itself — cleaning, thermal management checks, and capacitor life monitoring at manufacturer-recommended intervals. The PM motor has no brushes and requires minimal motor-specific maintenance beyond standard inspection. Overall, the additional VFD-related maintenance tasks are modest relative to the energy benefits in variable-load applications.
Does the CM/DV series require cooling water?
Yes. Like the fixed-speed CM/D series, all CM/DV models are water-cooled. Cooling water connections, flow rates, and inlet temperature requirements are the same as the equivalent CM/D model at the same power rating. If your facility does not have an adequate cooling water supply, the air-cooled CMN/D micro-oil series is worth considering, provided that its 2 PPM oil content is acceptable for your application.
Evaluate the CM/DV for Your Application
To determine whether the CM/DV variable frequency series is the right fit for your plant, share your required peak airflow (m³/min or cfm), working pressure, daily operating hours, and a description of how your demand varies across a typical shift or day. Our engineering team can assess whether the VFD configuration offers meaningful energy savings for your specific load profile, and confirm model selection accordingly.
Compare the full range of available options on the medium and low pressure air compressor series page before reaching out.
