How To Size a Rotary Phase Converter

If you’re relatively new to phase converters, the technical information you read on how to size a rotary phase converter may overwhelm you. To size your phase converter, you will need to know the type and specifications of your machine such as the kW, HP, kVA, or AMPs ratings as well as the voltage. This will determine your system’s style load such as resistive, CNC, hard starting, or light duty. Knowing your phase converter’s style load ultimately determines the capability of your system.

Please note: you can have a phase converter that supports a larger load than you currently need. In fact, it’s recommended that you opt for a bigger load—you’ll likely need it in the future.

Setup & Equipment Configuration In Your Facility Impacts the Phase Converter Sizing Process

When it comes to sizing your rotary phase converter, it’s extremely helpful to know the placement location. This will help customize the system to your individual needs. If you think your phase converter will be mounted on a wall separate from machines, portable, or operating with other components, a licensed technician is able to customize the sizing of your system. There are a variety of options to optimize the needs of your shop.

How Loud Is a Phase Converter When Running?

Despite the idler running to operate the third leg, phase converter systems are not distracting or excessively loud. We design and engineer our rotary phase converters to operate with an idler that runs quietly and efficiently—no matter the HP your phase converter needs. Our advanced mechanisms create a top-tier power supply that’s even more precise than utility-supplied three-phase power. Contractors and technicians across the nation choose to configure our selection of high-quality rotary phase converters.

Sizing 2:1 Rule of Thumb Method

Drawing from single-phase power to run a three-phase system requires a correct size rotary phase converter. To ensure you find equipment with a sufficient capacity, it’s best to use a 2:1 ratio. Doubling the HP rating of your machine is the most effective method to obtain the correct phase converter sizing as well as determine parameters of your budget. Please note: Companies may have different guidelines for labeling phase converter sizes. Getting the wrong component will likely impact cost analysis, planning, breaker sizing, and electrical rough-in.

Need help finding the right size phase converter for your needs? Get phase converter sizing help from our experts.

3 Benefits of Rotary Phase Converters

There are so many advantages to using rotary phase mechanisms within your shop. In addition to being a cost-effective alternative, these systems are incredibly user-friendly. Let’s unpack the top three benefits of a rotary phase converter.


It’s no secret that three-phase power runs longer and more efficiently than conventional methods. Our rotary phase converters are reliable, long-lasting components that maximize functionality.

High Power

With an optimal rotary phase converter size, you’re able to utilize three-phase power with a single-phase source. This prevents installing three-phase power lines, which is an extremely costly expense.


The idler motor within a rotary phase converter only takes the power needed to operate. This component enables the motor to run idle, which maximizes efficiency and extends longevity.

Additional benefits and features of a rotary phase converter include:

  • Built-in motor start control
  • Simple installation
  • 3-line power protection
  • Precise voltage stability
  • State-controlled starter circuit

Our Catalog Of Phase Converters

To learn more about different types of phase converters, transformers, or additional components, contact our team by phone at (866) 418-9060. Our staff will help you choose a correct phase converter size or capacity for your unique application. We offer different types of phase converters such as rotary phase converters, digital phase converters, and autostart phase converters. Our knowledgeable team members are committed to working with you to find a system that best fits your specific needs.

For over 50 years, Phoenix Phase Converters has helped customers find the right parts needed for their specific goals, and we’ll do the same for you. With hundreds of options in stock and a 36-month warranty to back up our services, you’ll see why we’re the top choice for converters, motors, and accessory components. Speak with our staff directly to learn more about our products, warranties, and policies.