Technical Support
Phase Converters: Single Phase to Three Phase Power
Complete buyer's guide
Phase converters — everything you need to know
Convert single-phase power to three-phase for CNC machines, compressors, HVAC, and entire machine shops. American-made since 1968.
40,000+
Units in service
50+ yrs
Engineering experience
3–200 HP
Available range
Lifetime
Panel warranty
Types
Which type of phase converter do you need?
Three technologies exist. One is right for almost every shop application.
Best choice
Rotary phase converter
True 3-phase · All applications
Uses a spinning idler motor to generate a real third phase. Full horsepower on all three legs — identical to utility three-phase.
- Runs CNC, compressors, HVAC, welders
- Powers multiple machines simultaneously
- Full-rated HP output on all legs
- Handles hard-starting loads
- Lifetime warranty on Phoenix units
Static phase converter
Start-only · Light duty
Capacitors start the motor, then drop out. Motor runs on single-phase only — limited to about 2/3 rated HP.
- Cannot run CNC or sensitive electronics
- Motor runs hot, wears faster
- Only one motor at a time
- Lowest upfront cost
VFD (variable frequency drive)
One motor · Speed control
Electronic conversion for a single motor with speed control. Creates problems when combined with CNC internal VFDs.
- One motor per VFD — not shop-wide
- Causes CNC alarm faults
- Good only for simple single-motor loads
- Adds speed control if needed
Sizing calculator
Find your converter in 30 seconds
Enter your largest motor's HP and select your load type — we'll tell you exactly which Phoenix converter you need.
Converter sizing tool
Based on 50+ years of field sizing experience.
10 HP
Minimum converter size20 HP
Recommended modelGP20NL
Starting price$2,663
SeriesNL Series (auto-start) for standard shop use
Running multiple machines? Add up all HP running simultaneously, then apply the multiplier for your hardest-starting load. CNC machines: include spindle, servo drives, coolant pump, and hydraulic unit — not just spindle HP.
Quick-reference
Sizing by equipment type
Common configurations and recommended Phoenix models.
| Your equipment | Motor HP | Min converter HP | Recommended model | Starting price |
|---|---|---|---|---|
| Lathe, drill press, small saw | 1–3 HP | 3–6 HP | GP3NL / GP5NL | from $749 |
| Milling machine, grinder | 3–5 HP | 6–10 HP | GP10NL | $1,955 |
| CNC mill (Haas VF-2, Bridgeport) | 5–10 HP | 20 HP | GP20NL | $2,663 |
| 10 HP air compressor | 10 HP | 25 HP | GP25NL | $3,709 |
| Large CNC or multiple machines | 10–20 HP | 40 HP | GP40NL | $4,820 |
| Full machine shop, large HVAC | 20–40 HP | 60 HP | GP60NL | $8,635 |
| Industrial facility, 40+ HP loads | 40–100 HP | 100 HP | GP100NL | $13,034 |
Applications
What are you powering?
Every application has specific sizing rules. Click yours for a dedicated guide.
CNC machines
Haas, Mazak, DMG Mori, Bridgeport
HVAC and refrigeration
Commercial AC, chillers, compressors
Woodworking
Table saws, planers, dust collectors
Agriculture
Irrigation pumps, grain dryers, augers
Welding and plasma
MIG, TIG, plasma cutters
Machine shops
Full shop, multiple machines, subpanel
Comparison
Phase converter vs. utility three-phase
Running utility service costs $10,000–$100,000+. Here's how the numbers compare.
| Phoenix phase converter | Utility 3-phase service | |
|---|---|---|
| Upfront cost | $749 – $13,000 | $10,000 – $100,000+ |
| Installation time | 1–2 hours | 2–12 months (utility scheduling) |
| Monthly cost | Electricity only — no demand charges | $50–$200/month demand charges |
| Portable if you move | Yes — take it with you | No — stays with the building |
| Available anywhere | Yes — any single-phase location | Limited — utility coverage required |
| Warranty | Lifetime panel + 10-year motor | N/A |
Why Phoenix
Built differently for 50+ years
Every unit hand-assembled, load-tested, and serial-tracked in Phoenix, AZ before it ships.
Lifetime panel warranty
Every control panel carries a lifetime warranty. Motors carry a 10-year warranty. No asterisks.
Engineer answers the phone
Call and talk to the person who built your converter. Free sizing, no pressure, no call centers.
NEMA 4 + TEFC standard
Weatherproof enclosure and cast-iron idler motor included on every unit — not optional upgrades.
Made in Phoenix, AZ
U.S. patented design. Family-owned two generations. 40,000+ units in service across all 50 states.
FAQ
Common questions
If your question isn't here, call (800) 417-6568 — we size systems free every day.
What size phase converter do I need?
The basic rule is to double the HP of your largest motor. A 10 HP motor needs a 20 HP converter. For compressors and HVAC, use 2.5x. For dust collectors and high-inertia fans, use 3x. Running multiple machines simultaneously? Add up all the HP running at once, then apply the multiplier. Use the calculator above for an instant recommendation.
Can a rotary phase converter run a CNC machine?
Yes — rotary phase converters power CNC machines in job shops across the country every day. The key is correct sizing. A CNC machine has a spindle motor, servo drives, coolant pump, and hydraulic unit — all drawing power simultaneously. Add all nameplate HP values, then size the converter at 2x that total. Don't size based on spindle HP alone.
How much does a phase converter cost?
Phoenix phase converters range from $749 for a 3 HP unit to $13,034 for 100 HP. The most common range for machine shops (10–30 HP) runs $1,955 to $4,480. Compare that to $10,000–$100,000+ to have the utility company install three-phase service — plus months of waiting for permits and scheduling.
What is the difference between NL and PL series?
The NL series is auto-start — power it up and it runs. Most popular for machine shops where the converter stays on all day. The PL series adds a built-in push-button start/stop control and voltage monitoring that automatically protects the converter if something goes wrong. PL is preferred when equipment protection is a priority.
Can I run multiple machines on one phase converter?
Yes — this is the most common setup. One converter feeds a three-phase subpanel, and all your machines plug into that panel. The converter stays on during shop hours; machines start and stop independently. Size for the total HP running simultaneously, not the total of all machines in the shop.
Do I need a transformer with my phase converter?
Only if your equipment voltage doesn't match your supply. A standard Phoenix converter on 240V single-phase produces 240V three-phase. If your equipment is rated for 460/480V, you need a step-up transformer after the converter. Phoenix can spec the complete system for 460V applications.
Is a phase converter as good as utility three-phase power?
For virtually all shop applications, yes. A properly sized Phoenix rotary converter produces balanced voltage within 3% leg-to-leg — within NEMA specs for motors and within tolerance for CNC controls and servo drives. In some cases, converter-supplied three-phase is actually cleaner than utility three-phase from a distant substation.
Not sure what size you need?
Tell us your equipment and we'll spec the right converter in under 5 minutes. 50+ years of sizing experience — free, no pressure.
(800) 417-6568Mon–Fri 7AM–5PM MST · Built in Phoenix, AZ · Lifetime warranty
Talk to a Phase Converter Engineer
📞 (800) 417-6568Free sizing help • Lifetime warranty • Made in USA • Mon–Fri 7AM–5PM MST