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Digital Phase Converter [Rotary and Solid State]

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There is a great variety of three-phase equipment that you can get your hands on! But what if you don’t have a 3-phase power supply?

The costs of installing three-phase utility power are quite high and this is where phase converters come in. The type of converter to use generally should come down to what type of equipment you have and how you are planning to use it.

Moderately to light loads that you are not planning to use up to their full HP potential could probably get away with Static Phase Converters (you can check out an article on Static Phase Converters). If you need to get the most power out of your equipment and/or planning to power the whole shop with it, you will need a Rotary Phase Converter (another article in the link).

The biggest problem with Rotary Phase Converters is that if it is not properly balanced with capacitors, it will produce rough power that could damage your equipment (a common situation, especially for DIY fans). Digital Rotary Phase Converters (CNC compatible) solve this problem by adding a digital controller that provides a voltage balance within a 2-5% range under 50-60% of the full load.

This is how voltage or phase imbalance reduces the motor’s HP rating:

Voltage imbalance Motor derating
1% 98%
2% 95%
3% 88%
4% 82%
5% 75%

Here is pictorial of the above table to elaborate more:

According to National Electrical Manufacturers Association (NEMA) MG-1 Standard, the maximum unbalance voltage that can be applied to an electric motor is up to 5%.

Phase imbalance also significantly reduces the life of 3-phase motors and has a great impact on their performance. Unlike other phase converters, Digital Phase Converter (or DPC) can safely and reliably transfer power to voltage-sensitive loads like:

    • CNC (Computer Numerical Control)
    • VFD (Variable Frequency Drive)
    • EDM (Electrical Discharge Machine)

This perfectly balanced three-phase voltage equipment offers the safe and efficient operation of any 3-phase load within its capacity, which includes (but is not limited to):

  • CNC equipment
  • Woodworking equipment
  • Metalworking equipment
  • Industrial machinery
  • Agricultural machinery
  • Foodservice equipment
  • Irrigation systems
  • HVAC equipment
  • Cranes
  • Submersible pumps
  • Sawmills
  • Elevators

Digital Phase Converters come in two types (this is what I figured out, due to limited and confusing information available on the web right now). They are:

  • Rotary Digital Phase Converter. This one comes with an idler motor and electronically advanced phase balancing systems, which makes it great for voltage-sensitive applications like CNC.
  • Solid State Digital Phase Converter. This one does NOT come with an idler motor. It uses AC/DC and DC/AC conversion systems in order to give you a third leg of power. So far, I only found Phase Perfect®  that does that, but I am sure there are some other versions out there (from China and not UL listed), but this one is made in the USA and tested out by Underwriter Laboratories.

Digital Phase Converter uses a double conversion technique where the input rectifier (which consists of IGBTs in series with inductors) converts AC (Alternate Current) power from utilities into DC current and then back to the AC. Insulated Gate Bipolar Transistors (IGBTs) are controlled by software in the DSP (Digital Signal Processor).

The output inverter of the Digital Phase Converter uses IGBTs to create AC power out of DC (Direct Current) and passes it through an inductor/capacitor filter in order to get it to sinusoidal waveform with less than 3% Total Harmonic Distortion (THD).

Here is PDF file of diagram for better detail.

The Digital Signal Processor (DSP) is a microprocessor that controls the whole phase conversion process. Its job is to monitor the input and output modules and maintain balance within three phases at all times.

DSP also serves a function of a surge protector and will shut down if over-voltage is detected. Voltage balance across three legs and a sine-wave output is a good formula for powering safely even the most sensitive equipment.

These types of converters generally operate with 95-98% efficiency.

Rotary Digital Phase Converter

Let’s start with Rotary Digital Phase Converters since I found quite a few of them. I will mention only ones that are made in the USA:

American Rotary

A very popular converter of this type is from American Rotary (models AD and ADX). Check out this short video on ADX Smart Series Rotary Phase Converter:

ADX - Smart Converter

After reading a bunch of forum posts, I did not notice people having problems with it. Besides, users also say that the customer support of this company is awesome!

So if you ever have any problems with this product, help is just a phone call away! Here is a full line of Phase Converter products from American Rotary (that includes Rotary Digital Phase Converters):

American Rotary AR, AD, ADX & AUL Rotary Phase Converter Overview

Here is a link to their line of converters.

North America Phase Converter

This company offers two types of Digital Rotary Phase Converters:

  • Smart-Boost™.  Offers an extra boost in the current for heavy-duty motors which are hard to start and require greater inertia. This type of digital rotary phase converters is best for motors in the compressors, fans, blowers and pumps.
  • Smart-Phase™. It offers tight voltage balance control for machines which are voltage-sensitive and for places where more than one loads are running at a time. This type is mainly perfect for VFD operated motors and machines which have more electronic equipment like in CNC machines.

Phoenix Phase Converters

Here are some features of Digital Phase Converters from this company:

  • Phoenix Digital Phase Converters w/ AutoStart. With all the features of Digital Phase Converts Phoenix company added scheduling functionality in their product. Operator can set the time for which converter remains on and when to turns off though a touch panel installed on the converter. Also, they offer WiFi, internet and Bluetooth compatibility.

Solid State Digital Phase Converter

Phase Perfect® is a very popular phase converter solution from Phase Technologies (and the only reasonable one I found so far, with some others claiming to be Digital Phase Converters and ending up being a Static one).

Phase Perfect offers two type of digital phase converters.

  • PHASE PERFECT®
  • PHASE PERFECT® ENTERPRISE

Both types have almost same features. But the first one model has the ability to withstand exterior environment even in harsh climates with temperature up to 50oC (122oF).

Let’s take a look inside of it:

EKM OmniMeter Pulse v. 4, Dash software, and Phase Perfect PT-330 solid state phase converter

Phase Perfect® Phase Converter provides a balanced undistorted output voltage to your equipment. Here is a link.


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