Rotary Phase Converter General Questions

A rotary phase converter is an electrical device that converts single-phase power into three-phase power. The third phase, also known as the generated leg, is created by an idler motor. The generated leg combines with the two single-phase lines to create three-phase power. This allows for the operation of three-phase equipment in locations with single-phase power without needing to upgrade the utility service.

Correctly sizing a rotary phase converter is extremely important for it to properly run your load. Generally, we recommend either sizing for the largest load it will start and run by itself or for the total of all the loads that it will start and run together. Each phase converter page features a sizing chart to use as a starting point.

Important Questions to Consider During Sizing:

  • What type of load (machine/equipment/motors) are you running?
  • What is the horsepower, amperage, or kVA rating of your load?
  • How old is the load/equipment?
  • Where were the machines, equipment, or motors made?

These are just some of the factors to consider when sizing a phase converter. Our sizing tools page is a helpful resource. You may also email us at [email protected] or call us toll-free at 877-545-2926 for professional sizing help.

CNC stands for Computer Numerical Control. There are multiple types of CNC machines, including lathes, mills, routers, and plasma cutters. Preprogrammed computer software guides the machine, turning raw materials into finished parts.

Computer-operated machinery is often highly voltage sensitive, requiring a balanced and consistent power supply to run. Pro-Line rotary phase converters are rated to run CNC machines by keeping the voltage balanced +/-5%. Additionally, TritonPro Maxx™ digital phase converters are equipped to run voltage-sensitive CNC machines. NAPCco phase converters are used to power Haas, Mazak, Hurco, FANUC ROBODRILL machines, and more.

The average life span for a rotary phase converter is 30+ years. NAPCco is a certified UL-508A panel shop. Every aspect of our product line was carefully considered during the design and engineering process to ensure our phase converters are built to last and meet the highest quality standards. Each component has the appropriate certifications and meets or exceeds the standards for its use. All components have a minimum rating of 100,000 starts and/or 50,000 hours of operation.

Yes, NAPCES is a UL 508A Industrial Control Panel Builder. Both our Pro-Line and Smart-Boost™ rotary phase converters can be UL-listed as an added option.

Yes, a properly sized rotary phase converter will produce balanced three-phase power for both resistive and inductive loads.

Yes, a single rotary phase converter can run multiple pieces of equipment, as long as it is correctly sized. In fact, many of NAPCco’s customers power their whole shop on just one rotary phase converter.

Yes, but you will also need a transformer. A rotary phase converter does not change the input voltage.  For example, if your input is 240 volts single-phase, then your output will be 240 volts three-phase.  In this case, a step up transformer (240 volt to 480 volt) is needed after the phase converter.  NAPCES offers a complete line of transformers for situations like this.

No, your machine will not lose power, as long as the rotary phase converter is sized correctly for the load. A NAPCco rotary phase converter generates a balanced three-phase output, allowing your equipment to run at its full rated power.

NAPCco rotary phase converters are extremely efficient.  More than 97% of the total power utilization is transformed into working power for your load.

 

ODP stands for “Open-Drip Proof,” and these motors are designed for indoor, dry environments. To keep the motor windings cool, vents on the sides of the motor increase airflow and ventilation. TEFC stands for “Totally Enclosed Fan Cooled,” meaning the motor has no vents and is cooled by an external fan instead. TEFC motors are suited for outdoor (wet or damp) use, since the motor’s enclosure prevents external contaminants from entering the motor’s interior. ODP motors typically run cooler than TEFC motors.

Both types have their advantages and disadvantages, as each is designed for different environments. However, the motor type has no impact on the phase converter’s performance, and both types effectively generate the third phase. NAPCco offers both types of idler motors.

Yes, in fact, most electric/utility companies recommend the use of a rotary phase converter. A phase converter is a fraction of the cost of installing utility three-phase. Additionally, phase converters are often faster and easier to install, and can be moved to different locations as needed.

Starting and Running Questions

Every rotary phase converter needs a motor starter (manual or magnetic) or some other approved motor starting mechanism, such as a disconnect switch. A circuit breaker is not motor-duty rated and is not an approved means for starting a phase converter. Every NAPCco phase converter includes a built-in motor starter.

A rotary phase converter, by itself, is in an idle state and draws only the amount needed to keep it energized. This is only a few kilowatts and in some cases less than one. The main electrical consumption depends on what the load draws. The phase converter is a simply a device electricity passes through on its way to the load.

A NAPCco rotary phase converter will generate a 3-phase voltage output equal to the single-phase voltage input.  NAPCco manufactures 208-250 volt and 480 volt units.

NAPCco units were designed for simple installation, and our technicians are always available to assist with installation questions. All wire terminations are made on large power distribution blocks, and a removeable back plate allows for the control panel to be easily mounted.

Installation must be performed by a licensed electrician and comply with National, State, and Local Electrical Codes.

Yes, a NAPCco rotary phase converter is designed to perform continuously with or without a load connected. Our rotary phase converters are balanced down to a no load condition; therefore, there is no minimum motor size you can run.

Power factor is the measure of how effectively current is converted into real power. NAPCco rotary phase converters are power factor corrected to help reduce wasted energy and improve efficiency.

Generally no, a rotary phase converter must start first before a load is applied.  Automatic controls can be added for unattended loads.  Please contact our applications support team for more details.

Mounting, Installation and Wiring Questions

A NAPCco rotary phase converter has two components: the idler generator and the control panel. The most common mounting option is to mount the control panel to a wall or solid surface, placing the idler motor near the control panel, typically on the ground. We also offer a floor mounting kit, allowing for the idler motor and control panel to rest on the same base plate.

Larger NAPCco units come with both the idler motor(s) and control panel in one large enclosure.

Yes, NEMA 3R enclosures and TEFC idler generators are available as an upgrade for outdoor locations.

Typically, you will need wire, conduit, connectors, and your single-phase power source (circuit breaker or disconnect switch). Depending on how the output is connected between the load and the phase converter, additional components may be required. Most are items you should be able to pick up at a local electrical distributor or home improvement center.

Phase converter installation must be performed by a licensed electrician and comply with all National, State, and Local Electrical Codes.

The single-phase service required depends on the three-phase load(s) you plan to connect to the converter. A NAPCco rotary phase converter can run on a wide range of input amperage. A general rule of thumb is to determine your three-phase load’s amperage and double that amount for your single-phase feeder amperage.

Yes, in fact, we recommend wiring into a 3-phase panel, also known as three-phase load center, when operating multiple machines. From the panel, each machine is connected a dedicated circuit breaker.

No, however, NAPCco recommends keeping them close together as a shorter wire run helps to minimize voltage drop.

The N.E.C. Article 455 governs the installation of rotary phase converters. Article 455.6 states that the input wire size shall not be less than 125% of the phase converter nameplate input full-load amperes (for variable loads) and/or not less than 250% of the sum of the full-load 3-phase current rating (for variable and fixed loads).  Minimum wire size recommendations are listed in the installation manual. NAPCco application engineers can help answer any questions pertaining to wire sizing.

A NAPCco rotary phase converter requires very little maintenance. We recommend periodic lubrication, cleaning, and inspection to ensure dependable performance.  Bearing grease may occasionally be needed. Check your installation manual for detailed maintenance instructions.

Please call us at 877-545-2926 or use our contact form …

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