You bought the machine and the nameplate says three phase. Your shop is single phase. Here are the five ways out, what each one actually costs you, and the constraint most people forget to check.
You found the right machine. Good price, right size, everything you wanted. Then you read the nameplate: 600V, three phase. Your shop has single-phase power, and the machine is already on a trailer.
This comes up constantly around Central Alberta — farm shops, acreage shops, small fabrication and machine shops, and anyone who buys used equipment at auction. The short answer is that it is almost always solvable. The useful answer is that there are four or five genuinely different ways to solve it, they cost very different amounts, and the right one depends on details most people do not think to check before they buy.
Before anyone can tell you what you need, these are the questions that matter.
Get those six answers together and the choice usually makes itself.
If the utility can bring three phase to your property at a sensible cost, this is the cleanest answer. Real three-phase power, balanced, no conversion equipment, no compromises, and every machine you ever add just works.
The catch is availability. In town it is often there or nearby. On rural property it frequently is not, and bringing it in can involve a significant customer contribution depending on distance and what is already on the line. There is no rule of thumb worth quoting here — the number depends entirely on your location.
What to do: contact your local distribution utility, give them your site address and an idea of the load, and ask what is available and what it would cost. That call is free and it sets the ceiling for every other option. If it comes back affordable, stop reading — take it.
A VFD takes single-phase power in and produces three-phase output for one motor. For a single machine with a single motor, this is often the best answer, and it frequently costs less than the alternatives.
Setting a drive up properly means entering the motor nameplate data, setting acceleration and deceleration ramps to suit the load, setting current limits, and wiring the machine’s controls to the drive’s inputs. A drive dropped in on default settings will often run on the bench and then fault under real production load. That pattern is covered in more detail under VFD overcurrent faults.
A rotary converter uses an idler motor to generate a third leg. Once it is running, it can feed several machines from one unit, which is what makes it the usual answer for a shop rather than a single machine.
For a shop with two or three conventional machines, a properly sized rotary converter is usually the sensible middle ground between one VFD per machine and a utility service upgrade.
The cheapest device on the shelf, and the one that disappoints most often. A static converter helps the motor start, then drops out — after which the motor runs on two legs.
The result is reduced output, commonly cited at around two-thirds of nameplate horsepower depending on the unit and the motor, and a motor that runs hotter than it should. For a machine that is lightly loaded and used occasionally, that may be acceptable. For anything that works for a living, it generally is not: you paid for a 7.5 HP machine and you are not getting 7.5 HP, and the motor is paying for it in heat.
It is worth knowing this option exists so you recognise it, and worth being clear that it is rarely the right choice for production equipment.
Sometimes the simplest fix is to replace the three-phase motor with a single-phase one of the same frame size. On a small machine — a bench grinder, a small saw, a light-duty pump — this is often the cheapest route and ends the problem permanently.
It stops making sense as horsepower climbs. Single-phase motors above a few horsepower get expensive, draw heavy starting current that your service may not like, and are not always available in the frame and mounting the machine needs. On a machine with its own three-phase controls, swapping the motor also means rewiring the control side.
None of these options create energy. Whatever the machine consumes still comes through your single-phase service, and on rural properties and older shops that service is frequently the actual limit.
A farm shop on a 100 amp service that already has a welder, an air compressor, shop heat and block heaters does not have much headroom left for a 10 HP machine. The symptoms when you exceed it are recognisable: the main trips under combined load, lights dim noticeably when the machine starts, or other equipment misbehaves while it runs.
This is why a load assessment comes before buying conversion equipment, not after. It sometimes changes the answer entirely — if the service needs upgrading anyway, the economics of a utility three-phase service look different. That assessment sits under panels and equipment power.
Used equipment brings a second layer of problems beyond phase count, and they are worth checking before the machine is on your floor.
Worth doing before you buy: send a photo of the nameplate. Five minutes on the phone before the machine is on a truck is a great deal cheaper than finding out after it is sitting on your floor and you have already paid for it.
Installing a converter or a drive, running a new feeder and adding a disconnect is installed electrical work. Work that requires a permit should have one, and permitted work is inspected by the authority having jurisdiction. Requirements change between code cycles, so anything you are unsure about is worth confirming against the current Canadian Electrical Code and your inspection authority rather than against how a previous shop did it.
For a single-motor machine with simple controls, usually yes, and it is often the best answer. For a machine with multiple motors, its own control circuitry or any electronics, it is not that simple. The nameplate and a look inside the control panel settle it quickly.
Neither is better in general — they solve different problems. One drive runs one motor very well and gives you speed control. One rotary converter runs a shop full of conventional machines. If you have one machine, start with the drive. If you have three and expect a fourth, look at the converter.
That is expected on a rotary converter — the generated leg behaves differently from the two supply legs. It is normal for motors. It is the reason sensitive electronics should not be fed from it, and the reason a machine that ran fine for years can misbehave when a digital control is added later.
Often yes, if the converter was sized with that in mind. The limit is usually starting the largest motor rather than total running load. Worth asking before you buy the converter rather than after you buy the second machine.
If it is on a static converter, that is the expected behaviour — the motor is running on two legs at reduced output. If it is on a rotary converter or a drive, it is worth measuring, because a machine running weak on what should be full three-phase power is usually telling you something. The same pattern appears when a leg is lost on a genuinely three-phase supply, which is covered under phase loss on a motor.
Probably not wrong so much as not yet corrected — rotation on a three-phase motor depends on the order of the legs, and it is a straightforward fix. It matters more than people expect on pumps, compressors and anything with a gearbox. See three-phase motors running backwards.
If you have a three-phase machine and a single-phase shop — or you are about to buy one — send the nameplate photo and a description of what else is in the shop. You will get a straight answer on which of these options actually fits, including when the honest answer is that the machine is wrong for the building.
Call 403-872-8698 or send the details through the service request form. Related work is covered under motors, motor controls and VFDs and machine and fabrication shops.
Grasse Electric serves Red Deer, Red Deer County, Blackfalds, Sylvan Lake, Penhold, Springbrook, Innisfail, Lacombe, Ponoka and Morningside.
Written by Todd Grasse, Red Seal Journeyman Electrician, Grasse Electric — Red Deer, Alberta. Published October 12, 2026.
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