Rotary Phase Converters
A spinning motor that generates true three-phase power from single-phase input. Here's how it works and why it matters.
How It Works
A rotary phase converter contains a three-phase induction motor — called the idler motor — that runs continuously once started. Single-phase power from your utility feeds in on two legs; the spinning idler generates a third synthesized leg, producing balanced three-phase output at your load panel.
Unlike static converters (which use capacitors only) or digital converters (which use solid-state electronics), a rotary converter creates a true rotating magnetic field. That means it handles motor starting surges, variable loads, and continuous duty without voltage distortion.
Key Specifications
- Input: Single-phase 230V (standard) or 460V with transformer
- Output: Three-phase 230V (NL/PL series) or 460V (NLT/PLT/NLTA/PLTA series)
- Voltage balance: ±2% on Phoenix units at rated load
- Starting capacity: Handles up to 3× rated load inrush for hard-start loads
- Duty cycle: Continuous — no duty cycle limits
Rotary vs. Static vs. Digital
| Feature | Rotary | Static | Digital |
|---|---|---|---|
| True 3-phase output | ✓ | ✗ | ✓ |
| Motor starting (full HP) | ✓ | Limited | ✓ |
| Multiple simultaneous loads | ✓ | ✗ | Limited |
| Continuous duty | ✓ | ✓ | ✓ |
| Voltage balance under load | Excellent | Poor | Excellent |
| Cost (for same HP) | Mid | Low | High |
When to Choose Rotary
Rotary converters are the right choice when you have multiple motors, need to start under load (compressors, dust collectors, CNC spindles), or run equipment continuously. They're the industry standard for machine shops, agricultural operations, and any facility that needs reliable 3-phase without utility service.
If you're running a single light-duty motor that doesn't start under load, a static converter is cheaper. If you need precise frequency control or have sensitive CNC drives, look at the Digital Phase Shifter R5.