Generator Alternator Guide: Brands and Sizing

The engine makes the power; the alternator turns it into electricity you can use. Choosing a generator alternator comes down to three things — how it mounts, how much it must deliver, and how tightly it has to hold voltage when a big load hits.

Single bearing or two bearing

A single bearing alternator bolts directly to the engine flywheel housing, with the rotor supported at the drive end by the engine itself. It is compact and self-aligning, which is why most packaged sets use one. A two bearing machine carries its own bearings at both ends and is driven through a coupling or belt — the choice when the alternator is not rigidly married to the engine. Get this wrong and nothing lines up, so confirm it before anything else.

Sizing a generator alternator to real load

Rate the alternator to the load, not to the engine badge. Motor starting is what catches people out: a direct-on-line motor can draw six or seven times its running current for a moment, and the alternator has to hold voltage through that dip. Size on both continuous kVA and starting kVA, then check the two against each other. Our notes on choosing a G-Drive engine cover the matching engine side of the same calculation.

The ranges we carry

We stock alternators from Stamford, Mecc Alte, Marelli, Marathon and Dingol, along with a Leroy Somer alternative range. Dingol covers the value end with single bearing machines from roughly 16kVA to well over 100kVA, while Stamford and Mecc Alte are the long-standing choices where spares support over decades matters. Alternator parts are available separately.

Voltage control is part of the package

An alternator is only as steady as its AVR. The AVR senses output voltage and adjusts field excitation to hold it constant as load changes — if you have not met one before, start with what is an automatic voltage regulator. We carry Caterpillar, Engga, Kipor and Kutai units, and there are specials on selected AVRs.

Behind the AVR sit the rectifiers that feed the exciter — a common and often misdiagnosed failure point when output collapses but the engine runs perfectly.

Send us the set details — engine, mounting and load — and we will match the alternator. Browse our alternator range or request a quote.