A side-by-side comparison of the three main phase converter technologies — so you can match the right tool to your application and budget.
Every factor that matters when choosing a phase converter.
| Feature | Static | Rotary | Digital |
|---|---|---|---|
| Power Quality | Poor (2/3 power after startup) | Excellent (balanced 3-phase) | Superior (±1–2% balance) |
| Price Range | $500–$2,500 | $1,500–$8,000 | $2,500–$15,000+ |
| Can Run CNC Machines | No | Yes | Yes |
| Multiple Machines | No (single motor only) | Yes (entire shop) | Limited (sized per load) |
| Noise Level | Silent | Moderate (60–70 dB) | Very Quiet (45–55 dB) |
| Standby Power Draw | None | Low (1–3 kW idle) | Very Low (<0.5 kW) |
Static phase converters are the cheapest option but only provide true three-phase power during motor startup. After startup, motors run on single-phase at approximately 2/3 rated capacity. Use only for single-motor, non-critical loads.
Rotary phase converters generate continuous, balanced three-phase power using an idler motor. They handle any load type, scale to entire shops, and cost a fraction of digital units. The industry standard for 90% of applications.
Digital phase converters use solid-state electronics for tight voltage balance (±1–2%). Quieter and lower standby draw, but 2–3x the cost and typically sized per-load. Best for specialty applications with strict power requirements.
A rotary phase converter uses an idler motor to generate continuous, balanced three-phase power — producing true three-phase output at all times. The rotating mass acts as a flywheel, smoothing voltage fluctuations and delivering utility-grade power quality. A static phase converter uses capacitors to provide a starting boost for motors — it only assists with motor startup. Once the motor reaches operating speed, the converter drops out, leaving the motor running on single-phase at approximately 2/3 of rated capacity. Static converters cannot run CNC machines, sensitive electronics, or multiple machines simultaneously. Rotary converters can run your entire shop from a single unit. For 90% of applications, a rotary phase converter from Phoenix is the correct choice.
Digital phase converters use solid-state electronics to generate three-phase power with extremely tight voltage balance (±1–2%). They're quieter and consume less standby power. However, they cost 2–3x more than rotary converters (typically $2,500–$15,000+ depending on capacity), are sized to specific loads rather than flexible shop-wide use, and have complex electronics that can be expensive to repair. Rotary phase converters deliver excellent balanced power at a significantly lower cost, can flexibly handle varying loads across multiple machines, and use proven technology that has been reliable for 40+ years. Many rotary converters installed in the 1980s are still running today. For most shops, farms, and factories, a rotary phase converter provides the best balance of power quality, versatility, and value.
To properly size a phase converter: (1) Identify all equipment you'll run simultaneously. (2) Find the Full Load Amp (FLA) or Service Factor Amp (SFA) rating on each motor's nameplate. (3) Add up the total amp draw of equipment running at the same time. (4) Select a phase converter rated above that total. General rules: size for the largest single motor that needs to start plus all concurrent loads. A 10 HP rotary converter typically handles a 10 HP main load, while a 15 HP converter provides headroom for startup surges and multiple machines. Over-sizing by 20–25% is recommended for shops that plan to add equipment. Phoenix Phase Converters offers free sizing assistance — call 1 (866) 418-9060 and a dedicated support agent will help match the right converter to your exact application.
Free sizing consultation. Lifetime warranty. Ships from 7 US warehouses.