Phase converters are essential devices used to convert electric power provided in one form into another, enabling the operation of three-phase equipment where only single-phase power is available. This capability is particularly useful in locations where three-phase power is not accessible or would be prohibitively expensive to install, such as in rural areas or in certain residential settings. Understanding how phase converters work involves exploring the different types available and their operational principles.

Types of Phase Converters

There are three primary types of phase converters: rotary, static, and digital (or electronic). Each type has its unique mechanism of operation and application suitability.

Rotary Phase Converters (RPC)

Phoenix Rotary Phase Converters are mechanical devices that generate three-phase power from single-phase power using an induction motor. The process involves two main components: an idler generator (which is essentially an induction motor) and a control panel. The single-phase power is first applied to the idler, which then generates the third phase through rotation. This newly created third phase, combined with the original single-phase power, provides balanced three-phase power output. RPCs are favored for their durability and ability to handle high-power and variable loads, making them suitable for heavy-duty industrial machinery.

Static Phase Converters

Static phase converters use electrical components like capacitors and relays to start three-phase motors running on single-phase power. However, once the motor reaches a certain speed, the converter disengages, and the motor continues running on single-phase power but with reduced efficiency. This type is less expensive than RPCs but is suitable only for applications where the motor does not require full power for its operation, such as light to medium-duty machinery.

Digital (Electronic) Phase Converters

Digital or electronic phase converters use solid-state electronics to generate a third phase from single-phase power. They are more efficient and provide a more stable and accurate phase conversion than mechanical or static converters. Digital phase converters are versatile, able to power both heavy-duty industrial machines and sensitive electronic equipment. They work by converting the AC power to DC and then back to AC in three phases, using sophisticated control algorithms to ensure the output power quality and stability.

How Phase Converters Work

Phase converters are devices used to convert single-phase electricity to three-phase power, allowing three-phase equipment to operate on a single-phase power source. There are several types of phase converters: Digital, Static, Rotary, and Variable Frequency Drives (VFDs), each serving different purposes.

Digital Phase Converters

Digital phase converters are primarily used to convert single-phase to three-phase power. These devices are composed of electronic components and do not use an electric motor. They are not suitable for adjusting the speed of an AC motor or for running resistive loads such as welders, heating elements, lights, or battery chargers.

Variable Frequency Drives (VFDs)

VFDs are mainly used to control the speed of AC motors by varying the frequency and voltage of the power supplied to the motor. The conversion from single-phase to three-phase involves three steps:

  1. **AC to DC Conversion (Rectifier):** Converts AC power to pulsating DC using diodes.
  2. **DC Smoothing:** Uses capacitors to stabilize the pulsating DC into a more consistent DC supply.
  3. **Inverter:** Similar to solar panel inverters, it uses IGBTs or MOSFETs to rapidly switch DC into a three-phase AC output.

VFDs typically run one motor at a time. While converting from single to three-phase is practical, the output power may not fully match the input in terms of efficiency and capacity. For motor speed adjustment, using an inverter-ratedmotor is recommended due to their enhanced insulation and robustness.

Static Phase Converters

Static phase converters are simple, cost-effective solutions for starting three phase motors. They use start capacitors to generate enough torque to start the motor, and once up to speed, the capacitors are disconnected. This type of converter is best suited for light to medium loads, and using incorrect capacitor sizes can lead to failure. When running, these converters power the motor with just two phases, causing reduced efficiency and potential overheating, typically delivering 50% to 70% of the motor's rated capacity.

Rotary Phase Converters

More complex and efficient than static converters, rotary phase converters use an idler motor (acting as a generator) to produce nearly full three-phase power. The setup includes start and run capacitors, and a control panel with a power block and relay or timers. High-quality rotary converters, like those from Phoenix Phase Converters, can deliver power close to true three-phase quality, suitable for demanding applications like CNC machines and woodworking equipment.

Phoenix Phase Converters

Known for robust designs, Phoenix Phase Converters offer equipment like the NEMA 4 rated TEFC (Totally Enclosed Fan Cooled) cast iron generator. This design is water and dust resistant, featuring thicker steel and powder-coated finishes for rust resilience. TEFC motors remain cooler due to metal fins that dissipate heat efficiently, providing superior protection and performance compared to ODP (Open Drip Proof) motors.


Rotary phase converters represent a robust solution for accessing three-phase power from a single-phase source, ensuring optimal performance for a wide range of equipment. With advanced features like NEMA 4 ratings and TEFC motors, Phoenix Phase Converters stand out for their reliability and efficiency, catering to even the most demanding industrial applications.