Permanent-Magnet Variable-Speed (PMVSD) on Water-Lubricated Compressors: Energy & TCO

Why speed control matters

Compressed air is one of industry’s largest energy users — the U.S. DOE estimates roughly 10 % of industrial electricity drives compressors, and ENERGY STAR notes electricity is about 76 % of a compressor’s lifecycle cost. Fixed-speed units modulate by load/unload (wasting energy); a PMVSD drive matches motor speed to demand, avoiding unloaded losses.

The TCO model (5 blocks)

1. Energy (≈ 70–76 % of lifecycle cost)

2. Acquisition

3. Maintenance

4. Water treatment / consumables

5. Decommissioning

Worked example

A 200 hp (≈ 150 kW) unit at $0.10/kWh, 6,000 h/yr, 0.85 load factor:

• Energy/yr ≈ 150 kW × 6,000 h × 0.85 × $0.10 ≈ $76,500/yr

• A PMVSD saving ~20–25 % part-load → ~$15,000–19,000/yr recoverable

**Placeholder:** Replace rates, hours and saving % with CMN’s verified figures and the user’s tariff.

10 questions to ask any supplier

1. Is the certificate model-specific (TÜV Class 0)?

2. What is specific power (kWh per m³/min) at the duty point per ISO 1217?

3. PMVSD turn-down range and part-load efficiency curve?

4. Water-circuit treatment and service interval?

5. Star-wheel expected life and replacement cost?

6. Noise level at 1 m?

7. Lead time and local service partner?

8. Spare-parts availability?

9. Heat-recovery option?

10. Reference sites in my industry?

Request an energy report with your duty profile.