Sizing a Phase Converter for different applications

The Phase Perfect allows for flexibility in getting power to your 3-phase equipment. Two to three times the starting capacity of a rotary converter, no need to balance capacitors, power factor correction to make the most of available power, a single Phase Perfect is capable of running your entire shop or bank of changing loads.

Typically, you would choose a Phase Perfect rated above the sum of total current drawn for all connected loads. However, Phase Perfect’s can certainly be oversized, or split into multiple units, to better accommodate the available incoming power.


Scenario #1

Available power spread across multiple panels

In many cases, a small commercial building in a mixed commercial/residential area may only have single-phase power available. It is common in this scenario to have multiple panels with less available service. This is often done to reduce cost, 400-600 amp and larger single-phase panels are available, but cost significantly more than multiple 200-amp panels.

For Example:

Customer needs to run 2 sets of VRF units with 2 condensers each (4 total) for a new HVAC installation. They are choosing to run 3-phase units for any of a long list of reasons. Read more about phase conversion and hvac. The data sheet shows each condenser draws an MCA of 44 A @ 230 V. 44 multiplied by 4 equals 176 A @ 230 V. The customer would then typically choose a PT060 with a max output of 190 A @ 230 V. All of these amperages are three-phase.

Looking at the electrical drawings, you might find that each unit is spec’d with 200 A single-phase service panel. The PT060 requires a max input of 329 A. This is easily overcome by simply using two PT030 units to power the VRF units separately. Each PT030 can supply 95 A from 165 A of single-phase supply. Not a hard problem to overcome but illustrates the importance of not only checking the total load, but also the available max service size.


Scenario #2

Start-up CNC shop planning for the future

Having helped thousands of entrepreneurs get their machining businesses off the ground, we know getting that first machine up and running is exciting. We also know even before that first machine gets powered up, many machining startups are already thinking about their second and third machines.

For Example:

Perhaps the first CNC machine tool (mill, lathe, etc) has been purchased for a startup-up machining shop. The shop will probably want to add another machine in the next year or two. Not knowing the current draw on any future machines makes this somewhat uncertain, but one can still create future capacity, which can then be used to size that future equipment. To properly size a phase converter for this scenario one must determine the max service size they are able to use for the phase converter.

Let’s assume there is 225 A of single-phase available in this shop and 80 A needs to be set aside for things like lights, a small auxiliary heater, an air compressor, and some standard wall outlets. This leaves 145 A of single-phase available to run the first CNC and any future equipment. The largest phase converter that can be run with the 145 A available is a PT020, a 20-horsepower rated unit, with a max amp draw if 111 A.

The PT030, a 30-horsepower rated unit, requires 165 A of single-phase. By reconfiguring the shop with LED lights and a different heat source, it may be possible to make enough power available to install this larger converter and provide more future headroom for equipment.

It is extremely important to stay within the limits of the available service or risk fire.


Scenario #3

Can I run a large Phase Perfect on my small electrical service?

Sometimes a temporary situation arises where three-phase power is needed, and it would work best to be able to use an oversized Phase Perfect.

For Example:

Let’s assume a phase converter is needed to run an entire large shop, but only enough 3-phase power is required to run a 7.5-horsepower lathe in a garage until that larger shop is ready to be moved into. The garage service is limited to 100 A and the new facility will have 400 A. The customer really wants to purchase a PT040 now to save time and money in the future. The PT040 will pull a max of 225 A on the input, and as such would seem to be grossly oversized for the 100 A garage service. This is true, but only running one machine in the garage, they will never exceed the 100 A service.

The PT040 can be wired temporarily to a, for example, to a 60 A two-pole breaker in the garage service panel. If this breaker is overloaded because the lathe pulls too much current from the Phase Perfect, it will trip and both the converter and the lathe will shut down. This breaker will have done its job, however. The takeaway: yes, the Phase Perfect may be oversized, as long as the load attached to the Phase Perfect is not oversized with respect to the available service.


Doing the math

The Phase Perfect works on a factor of 1.73. For every 1 amp of three-phase drawn on the output, 1.73 A will be pulled on the input. If the Phase Perfect has the proper breaker size in front of it, there will be no issues. Any Phase Perfect will run just fine on a 20 A breaker, just know that the breaker may trip effectively limiting the output. An equivalent rotary phase converter to a PT030 would need to be at least twice the size. Good luck trying to start a 60-75 horsepower rotary on most single-phase services.

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Common terms related to phase conversion technology used throughout this website and across the internet.

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These pages contain comparisons of phase conversion technologies, including static, rotary, and digital phase conversion, applied to simple and complex scenarios.

Phase Perfect® provides uncommon value in Phase Conversion Technology

Phase Perfect®

The original Phase Perfect® supplies power to some of the most demanding applications available under some of the most challenging conditions imaginable. Utility-quality three-phase power anywhere you need it.

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Phase Perfect® Enterprise

The Phase Perfect® is also available in a compact, high-value, configuration where the customization options of the original are not required. These Enterprise models have the same modern digital phase conversion technology inside as the original.

See the Phase Perfect® Enterprise