1. Basics: kW, kWh, and kVA
kW (kilowatt) = Instantaneous “power”
How much power is used at a moment in time.
Example: 10 kW when cutting, 2 kW in standby.
kWh (kilowatt‑hour) = Accumulated “energy”
Electricity bills are based on kWh × unit price.
Example: 10 kW for 1 hour = 10 kWh.
kVA (apparent power) = “Capacity” of the supply
A guide to maximum load and contract power.
Convert to average kW by multiplying the power factor (PF).
Rule of thumb: Average kW ≒ kVA × PF × utilization
2. Reading catalogs (MC / NC lathe)
Machining centers
| Item | Meaning | Energy‑saving viewpoint |
|---|---|---|
| Required power (kVA) | Capacity at max load | Right‑size contract; avoid overspec |
| Spindle motor (e.g., 26/22 kW) | 30‑min / continuous ratings | Evaluate on continuous side; cap peaks |
| Feed axis motors (X/Y/Z) | Rated power of each servo | Optimize accel/decel and use regeneration |
Example “26/22 (30‑min/cont.)”: use the continuous side for energy studies.
NC lathes (incl. multi‑tasking)
| Item | Meaning | Energy‑saving viewpoint |
|---|---|---|
| Main spindle (L) | Left spindle power | Tune cutting conditions to reduce load |
| Sub spindle (R) | Sub spindle power | Manage concurrency to level peaks |
| Rotary tool spindle | Milling spindle rating | Shorten use time; proper rpm/feed |
Multi‑tasking peaks depend on concurrency (main × sub × rotary). Program/setup to flatten peaks.
3. Old vs. latest energy‑saving machines
| Viewpoint | Old model (example) | Latest energy‑saving model (example) | Effect |
|---|---|---|---|
| Standby power | 2.5 kW | 1.2 kW | −52% |
| Avg. while cutting | 12.0 kW | 9.5 kW | −21% |
| Monthly energy | 5,800 kWh | 4,300 kWh | −26% |
| Auxiliary control | Always ON | Inverters + auto control | Less ON‑time |
| Regeneration | None / limited | Standard / enhanced | Lower losses |
4. Operational measures that work now
① Auto‑stop in standby
Automatically stop or reduce power in idle time. Eliminates “left ON” by mistake.
② Eco modes & setup review
Use off‑peak tariffs; optimize concurrency to level peaks.
③ Inverters for auxiliaries
Optimize coolant/air flow and ON‑time. Cut “invisible power”.
④ Optimize accel/decel
Extreme speed isn’t always better. Balance quality and energy.
5. GX (CO₂ conversion) and internal buy‑in
| Energy savings (kWh/month) | CO₂ reduction (t‑CO₂/year) | Notes |
|---|---|---|
| 500 | ~2.4 | Using 0.4 kg‑CO₂/kWh |
| 1,000 | ~4.8 | Same |
| 1,500 | ~7.2 | Same |
6. Model comparison checklist
| Item | Check | Memo |
|---|---|---|
| Required power (kVA) | □ Low □ Std □ High | |
| Standby power (kW) | □ Low □ Std □ High | |
| Auxiliary control (inverters / auto‑stop) | □ Yes □ No | |
| Regeneration | □ Yes □ No | |
| Room to optimize concurrency | □ High □ Mid □ Low |