This is the perfect place to use a phase converter, a device that converts single-phase power to three-phase power. Phase converters come in various shapes and sizes, costing from a few hundred dollars to many thousands, depending on the HP rating and type. The phase converter will artificially generate the third leg of a three-phase system from the two poles of a single-phase system.
There are three basic types - static-phase converters, rotary-phase converters and solid-state phase converters. The static units consist of a several capacitors and often a transformer, sized to the amp draw of your pump motor, to generate the third leg of three-phase power. They have been around for a long time and are the least expensive of the three types. Their advantage is price, and their disadvantage is that they do not provide as closely balanced power as the more expensive units do (see Figure 1).
For applications that require stricter control on the power, solid-state phase converters are the best (see Figure 3). They have the advantage of providing very clean power with no harmonics or distortion. They are very efficient and operate in conjunction with the load motor at nearly unity power factor. They can power multiple loads and can be located remotely from the load. Some pump installers use them in situations where there already is three-phase power available, but it is so far out of balance it will not safely run a pump. In this case, a solid-state phase converter is hooked to two legs of the three-phase power and the pump gets perfect three-phase power from the converter.
If you have access to the Internet, there is a ton of technical and supplier information on phase converters. Also, check with your local pump distributor. He may well have a source of phase converters and offers the advantage of being there for you if there is a problem.
Next month, we will continue our series on the electrical side of pumped water systems with a look at three-phase control panels. 'Til then ….