Single-phase or three-phase generator: how to choose

Choose a single-phase generator (220-230 V) if your installation is single-phase with no three-phase motors, which is the case for most homes. Choose a three-phase generator (380/220 V or 400/230 V) if your building has a three-phase supply or three-phase motors (pumps, lifts, machines). Our whole Perkins-engine range, from 13 to 2,000 kVA, is three-phase.

Single-phase or three-phase: what is the difference?

Single-phase uses one phase and a neutral. Three-phase uses three phases and a neutral: you measure about 380 to 400 V between two phases and 220 to 230 V between a phase and the neutral.

In the DRC, the grid supplies 220 V single-phase and 380 V three-phase, at 50 Hz. The datasheets of our Perkins-engine sets give 400/230 V or 380/220 V, at 50 Hz.

Three-phase power runs three-phase motors, such as some pumps, lifts and workshop machines. It also serves buildings that need a lot of power.

How do you know if your installation is three-phase?

Look at the incoming supply and the main breaker. A single-phase installation receives two wires: one phase and a neutral. A three-phase installation usually receives four: three phases and a neutral.

Also check the rating plate of your largest motors. A three-phase motor usually carries the "3~" symbol and a voltage of 380 or 400 V. If in doubt, ask a qualified electrician.

Can you plug 230 V appliances into a three-phase generator?

Yes. A three-phase generator also supplies 230 V single-phase circuits, between a phase and the neutral. But each phase carries only about a third of the generator's rating. A 20 kVA set therefore supplies about 6.7 kVA per phase.

Single-phase loads must be spread across the three phases. If they all sit on the same phase, that phase is overloaded while the generator looks lightly loaded.

Have a qualified electrician do the wiring and phase balancing. Our installation and commissioning service can take care of it. To work out the current per phase, see our guide kVA vs kW.

Which single-phase and three-phase sets are in our range?

Our air-cooled range includes both single-phase and three-phase models. Our water-cooled range is entirely three-phase.

The Brux BX6500DSE and the Brux BX6500DSE3-3D show the choice clearly: the same 5.75 kVA output, one single-phase 220 V, the other three-phase 380/220 V. See all our silent diesel generators and our diesel generators.

What if your single-phase need is above 9.4 kVA?

Our single-phase range stops at 9.4 kVA, with the Brux BX11000DE. Above that, all our generators are three-phase.

In our finder, a single-phase need above 9.4 kVA therefore has no match. The answer is a three-phase set, with the single-phase circuits spread across the three phases.

For example, a 20 kVA set with a Perkins 404A-22G1 engine supplies about 6.7 kVA on each phase. Your electrician spreads the circuits of the house or premises across those three phases.

How does the finder help you choose?

Our finder asks for your electrical system: single phase, three phase or not sure. With "Not sure", it offers sets of both types. Use it to work out your generator size.

Before installation, read our guide Installing a generator safely as well.

Frequently asked questions

What should I choose if I do not know whether my house is three-phase?

Select "Not sure" in the finder: it offers sets of both types. Your electrician or our team then confirms the right choice.

Can a three-phase generator supply a single-phase house?

Yes, if the circuits are spread across the three phases. Each phase supplies only about a third of the generator's rating.

Sources: manufacturers' datasheets (Perkins engines, Bison and Brux generators), MK Energies & Services finder method.