FAQ

It depends on whose unit you buy. Each maker publishes its own rule for its own units. American Rotary's buying guide doubles it: a 10 hp motor needs a 20 hp converter. Phoenix's sizing guide starts at 2x for standard loads and goes to 2.5x or 3x for hard-starting or high-inertia loads. NAPCco rates each unit by how hard the load starts, so its PL-10 carries 7.5 hp on an easy load and 4 hp on a very hard one. Phase Technologies rates its Phase Perfect units to start a motor up to their own nameplate hp on models below 50 hp. We show each rule with the math and don't pick one.

Yes. American Rotary's FAQ says to add 25 to 50% capacity for hard-starting loads such as compressors and punch presses, and does not say what the percentage is added to. Phoenix's sizing guide puts piston compressors at 2.5x. NAPCco's tier table gives each unit a lower hp rating for hard and very hard loads.

Phoenix's sizing guide says to round up to the next available converter size. The other makers we've read publish no rounding rule.

For one motor, a VFD with single phase input can do it, if the motor fits inside the drive's single phase rating. Lenze's application note says most VFD makers stop at 3 hp for single phase input. Invertek publishes 5 hp for its E3 drive. Phoenix's CNC guide says VFDs work for single-motor uses such as a spindle, and that a VFD cannot power several motors at once. If the machine has its own starter, contactors or controls, ask the drive maker before you buy.

Because you get about two thirds of the motor's rated horsepower. Phase-A-Matic states "approximately 2/3 rated horsepower" under its Method No. 1, and Phoenix says roughly two thirds. After the start, the motor runs on single phase power, which American Rotary's CNC page says is hard on 3 phase equipment and rules out CNC. A static unit runs one machine at a time.

Rotary runs several machines from one unit. Digital publishes tighter voltage balance: Phase Technologies states 2% or less for its current Phase Perfect models, and Phoenix states plus or minus 1% for its GPX line. American Rotary publishes 2 to 5% between phases under load, and 1 to 5% on its MicroSmart control. Digital also publishes a standby power figure; no rotary maker we've read publishes one. "Digital" means different designs at different makers, so check the design in the maker's words first.

No. Hammond Power Solutions' FAQ says a transformer cannot convert a single phase source to 3 phase. You need a phase converter or a VFD.

A licensed electrician. American Rotary's manual says installation should be done by a licensed electrician familiar with phase converter installations. Phoenix's installation guide says the same. Phase-A-Matic and Phase Technologies say a qualified electrician. Phoenix's warranty excludes installs that don't meet local electrical code. We don't give wiring instructions.

Your electrician sizes them to the National Electrical Code (NEC) and local code. American Rotary publishes a breaker and copper wire table for its own units at 240V; other makers' units differ. If your panel is small, ask your electrician whether the service can carry the converter before you order.

Ask your local inspector before you order. American Rotary's UL page says to check with your inspector before ordering to learn what is required to pass inspection. Phoenix's installation guide names NEC Article 455 as the article that covers phase converter installs.

Your CNC maker's manual decides what the control accepts. The converter makers publish: Phoenix's CNC guide, within 2 to 3% for CNC; American Rotary's CNC page, plus or minus 5% or better, with its MicroSmart control stating 1 to 5%; Phase Technologies, 2% or less on current Phase Perfect models; Phoenix GPX, plus or minus 1%. We promise nothing beyond the converter maker's published figure.

A rotary converter alone won't do it. Phoenix's 480V page says a rotary converter's output matches its input voltage, and its answer is a rotary converter plus a step-up transformer. We don't sell transformers yet. A 480V machine is a hand-off: call us and we point you to the maker's engineers, who size the package.

Rotary units make some noise. The makers that publish a figure state different test conditions and none names a test standard, so we don't compare their numbers on one line. Phoenix's comparison table calls its digital units "Very Quiet (fan only)". Placement, per Phoenix's installation guide: indoors or under cover, out of rain, in a ventilated space, near the panel. Outdoors only in an enclosure the maker rates for it.

Phase Technologies publishes standby watts per model for its digital units. American Rotary's FAQ says a rotary converter "uses approximately 3–10% of rated HP when running but unloaded (idler running only)". On a 10 hp unit that is 0.3 to 1 hp, by American Rotary's figure. No other rotary maker we've read publishes one.

UL listed means UL tested a sample of that product and found it meets UL's requirements, per American Rotary's UL page. Makers word listing differently, and some cities also want the UL documents. Each product page carries the maker's listing words for that exact model, quoted. Check with your inspector before you order.

Makers rate their units on different bases. American Rotary's manual rates its AD/ADX 10 at a 5 hp largest load and 10 hp total. NAPCco's PL-10 carries 4 to 7.5 hp depending on how hard the load starts. Phase Technologies rates its PT010 to start a 10 hp motor. Compare the maker's largest-motor figure for your load, not the model number.

The maker's warranty. Terms differ by maker and by part, and each product page states them in the maker's words. We help you file the claim. We add no warranty of our own.

Yes, if the unit is unused: not wired, not energized, original packaging kept. See Returns for the window and who pays return freight.

A converter arrives on a pallet by LTL freight. Small drives arrive by parcel. Before you sign, inspect the crate and note any damage on the delivery receipt. See Shipping and the freight delivery checklist.

Yes. Call (855) 923-2610 with the motor nameplate: horsepower, volts and full load amps.