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Rotary Phase Converter Details


Phase Converters...

Phase Converters convert single phase power to industrial 3-phase power. Different types of phase converters exist, and they each have a certain method to achieve the conversion. Because American Rotary offers every type of phase converter available...Rotary, Digital, CNC, and can always be sure that we will recommend the method that is preferred for your specific application!

Rotary Phase Converters are a cost-effective and efficient means to start and run 3-phase motors on single phase power at 100% of their rated horsepower. Rotary phase converters can be used with heavy loads, resistive loads, multiple motor loads, multiple speed loads, and CNC equipment.

Rotary Phase Converter Details

What different models of Rotary Phase Converter are there?

American Rotary offers three main types of phase converter controls. The controls differ in the way that they start the phase converter itself, and the way that they interact with changes in the power supplied to your facility. Power changes can occur based on loads that are started in your facility, or external factors can be involved. The three main types we offer are Basic, CNC, and Digital CNC controls.

  • Basic controls provide true three phase power, with the voltage on the three lines being within 10% of one another. This is a great way to go for a very cost effective phase converter solution, and this is the type of controls that the majority of phase converters on the market use.
  • CNC controls are more sophisticated than a basic unit, and these units deliver voltage balance within 5% for all three lines. This tighter tolerance is required for CNC equipment, and also is a benefit to non-CNC three phase loads.
  • Digital CNC controls are the most sophisticated way to control a rotary phase converter. These units provide the most protection to the idler/generator components of the converter, and they allow for increased torque that can be required for extreme starting loads.

Is it expensive to run an American Rotary CNC phase converter?

GENTEC American Rotary CNC phase converters were specifically designed for low cost operation. In our efficiency ratings, we use the term "real power" to define what the power company ultimately charges the customer. We list the "Idle Power" figures in the detailed specifications of all rotary CNC phase converters in our product line. Using the cost per kWhour in your area (the national average is $.08/kWhour), and "Idle Power" figure from the specifications table, you can figure the cost to run our CNC phase converters per hour with the following equation:

Cost To Run (per hour) = Real Power (kW) x ($/kWhour)

A mid-sized 10HP American Rotary CNC phase converter would cost approximately $.07/hour at idle! When the CNC phase converter is under a load, the idle power shifts a little bit, but is considered to be insignificant.

Will American Rotary CNC phase converters dim the neighbor's lights?

Absolutely not! GENTEC American Rotary set out to design a custom CNC phase converter generator that would drastically reduce the inrush current upon start-up. The results were so dramatic that the GENTEC/Baldor motor generator was granted a soft-start rating!

What does Soft-Start have to do with CNC phase converters?

Our exclusive motor-integrated soft-start is built directly into the motor/generator housing and drastically reduces inrush (starting) current by softening the initial starting torque required to spin the generator. This greatly reduces, or even eliminates the power company "demand charges" that are so often associated with operating CNC phase converters. Engineers at GENTEC and Baldor worked together to design our custom three phase motor generator to reduce the inrush current upon start-up. The resulting 83% reduction of inrush current earned the GENTEC/Baldor motor generator a Soft-Start rating!

Is there a downside to using Soft-Start phase converters or CNC phase converters?

No. American Rotary CNC phase converters will provide all of the power required for heavy-duty and hard starting applications. Coupled with balanced pure sine wave output and power factor correction, American Rotary CNC phase converters are perfect for CNC and other voltage sensitive applications.

What about high "demand charges" for rotary phase converters?

American Rotary CNC phase converters have corrected power factor to, among other benefits, keep the amount of current produced by the power company (demand) to power the rotary converter to a minimum. Corrected power factor also reduces the cost to run our rotary CNC phase converters in industrial areas where additional "real power" demand charges can occur. American Rotary's proprietary soft-start CNC phase converter generator typically eliminates demand charges.

Is it safe to use American Rotary CNC phase converters on CNC equipment?

Yes! American Rotary CNC phase converters are designed to operate CNC equipment and other voltage sensitive applications. Our CNC phase converters are precision balanced under load and no-load conditions +/-5% or better, as required by CNC equipment manufacturers such as Haas, Fadal, Hurco, and others. American Rotary's custom CNC phase converter generators are manufactured with ISR (Inverter Spike Resistant) magnet wire. The development and use of ISR magnet wire virtually eliminates the spikes that are common in CNC applications.

Are American Rotary CNC phase converters loud?

American Rotary CNC phase converters are extremely quiet! The noise associated with a typical CNC phase converter can be placed into four categories:

  • By nature, electric motors of any sort will vibrate to some degree, however minutely, which will create mechanical noise in CNC phase converters. In addition, improper mounting - such as bolting a motor generator to a rigid structure or floor - will cause vibration in the bearings. Rubber isolation mounting feet virtually eliminate all mechanical noise, and also extend the life of the generator.
  • Humming or buzzing is electromagnetic noise which is caused by unbalanced currents and voltages in the windings. American Rotary CNC phase converters are precision balanced thereby eliminating electromagnetic noise.
  • Friction in the ball bearings causes bearing noise and is most commonly heard in motors manufactured in China. American Rotary CNC phase converter generators utilize precision high speed bearings and are manufactured entirely in the United States.
  • Whirring, or aerodynamic noise, is created by air displacement when a fan is used to cool a generator. TEFC motors are often used in CNC phase converters and are particularly loud because they require a lot of air for cooling. American Rotary CNC phase converter generators have extremely efficient cooling methods thus greatly reducing any aerodynamic noise.

Do I have to mount the CNC phase converter generator and the control panel together?

Regardless of how quietly American Rotary CNC phase converters operate, some shops prefer to mount the generator away from the control panel. American Rotary CNC phase converter panels are not mounted directly to the generator which allows a variety of mounting options to best suit the area they serve.

What about CNC phase converter installation?

American Rotary CNC phase converters come with easy to use instructions and installation procedures. A step-by-step installation pictorial available on this website, and you always have access to our 24/7 toll free technical support.

Can I run multiple machines with my American Rotary CNC phase converter?

Absolutely! American Rotary CNC phase converters are rated to run multiple machines and motor loads. This capacity is only limited by the current available as long as the rotary phase converter is sized for starting the largest load. American Rotary CNC phase converters are balanced from a no load condition so there is no minimum to how small a motor you can run on a much larger phase converter. CNC phase converters often run multiple loads, but we recommend that you call our engineering department for sizing assistance. Toll free 1-800-458-3687

Determine the load type of the application, and then consult the chart below. 
Please call us toll free at 1-800-458-3687 for sizing assistance and/or a professional recommendation.

  • Easy - no flywheel, clutch, little resistance/inertia, 1-2 times full load current upon start-up
  • Medium- machine inertia, medium resistance, 3-4 times full load current upon start-up
  • Hard - flywheel, no clutch, starts against load, 5-6 times, or locked rotor current upon start-up
  • Very Hard- elevator, hydraulic pump, equipment under continuous load etc
  • Frequent Start- instant reversing, heavy running loads
  • CNC - turning centers, PLC's, EDM, CNC machining
  • Resistive - heaters, transformers, welders, power supplies etc.
Rotary Phase Converter Largest HP Motor Load Maximum CNC Load Max Total Load Combined Equip Operating Cost
HP kW Easy Med Hard Amps kW HP* Amps kW ($ per/hr)
3 2.2 2 2 1.5 0-5 0-1.5  1.5  9  2.7  $.01
5 3.7 3 3 2 0-8 0-2.4  2.5  15  4.5  $.015
7.5 5.6 5 5 3 0-11 0-3.3  3.75  22  6.6  $.02
10 7.4 7.5 6 5 0-15 0-4.5  5  28  8.4  $.03
15 11.2 10 10 7.5 0-20 0-6  7.5  42  12.6  $.045
20 14.9 15 12 10 0-25 0-7.5  10  54  16.2  $.06
25 18.6 20 15 10 0-30 0-9  12.5  68  20.4  $.07
30 22.4 25 20 15 0-42 0-12.6  15  80  24.0  $.09
40 29.8 30 25 20 0-55 0-16.5  20  104  31.2  $.12
50 37.3 40 35 25 0-70 0-21  25  126  37.8  $.15
60 44.7 50 40 30 0-80 0-24  30  150  45.0  $.18
80 58.7 60 50 40 0-110 0-33  40  208  62.4  $.24
100 73.3 80 70 50 0-140 0-42  50  252  75.6  $.30
120 88.0 100 80 60 0-160 0-48  60  300  90.0  $.36
* total spindle horsepower: total kW of the machine must be less than max CNC load kW.
† combined loads do not include CNC or voltage sensitive loads.
‡ cost based on national average of $.10/kWhr.
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