What to consider when buying a generator set

Time：2026-07-28      Source：     Author：admin

                What to consider when buying a generator set

If you've ever shopped for a generator set, you've probably run into this: two sets with the same diesel engine and generator specs, yet a huge price difference. Why? The catch is hidden in the generator’s winding. To cut costs, many assembly plants fit their generators with 5/6-pitch windings.

Here's the trap: a 5/6-pitch generator will pass every test. A no-load run, even a light 60% load — everything checks out fine. But put it into real, continuous long-term use, and the problems start creeping in one after another: meters jumping around for no reason, relays tripping randomly, downstream equipment quietly overheating and wearing out, and in severe cases the neutral cable overloading and running hot — a fire hazard waiting to happen. The reason none of this shows up during testing is simple: all the defects of a 5/6-pitch generator are hidden, chronic problems.

Severe waveform distortion, badly compromised power quality. A 5/6-pitch winding produces a poor sine wave, loaded with harmonics, and voltage distortion beyond acceptable limits. Under light or no load, it doesn’t show. But hook up a nonlinear load, and harmonic noise starts wreaking havoc.

Multiple units can't be paralleled reliably, so forget about future capacity expansion. Too much harmonic distortion means the voltage waveforms between units won't match, and paralleling them creates a massive circulating current. Best case, the breakers can’t close and paralleling fails. Worst case, the whole set shakes violently while the windings keep overheating.

Precision instruments start giving bad readings — and it’s tough to diagnose. High-order harmonics directly interfere with measuring instruments, causing drifting and unreliable readings.
Automated controls start frequently misbehaving. PLCs, AC relays, and other low-voltage components are extremely sensitive to harmonic noise. That noise induces stray voltage in coils, so relays engage or trip at random and the entire automation sequence falls apart.

Wasted energy turns straight into heat — fuel costs climb, and operating costs go up. Harmonics can't do any useful work; they just get turned into extra heat.
Everything downstream ages faster. Harmonics increase eddy-current losses in motors & transformers, so all your equipment runs hotter than it should, long-term, degrading the insulation.

The biggest danger: neutral-line current exceeding rated limits, which can easily start a cable fire. In most wiring setups, the neutral cable's cross-sectional area is only 1/2 or even 1/3 that of the phase conductors. Pair a 5/6-pitch generator with nonlinear loads like variable-frequency drives or switching power supplies, then third-order harmonics pile up on the neutral line. Neutral current can reach up to 1.8x the rated phase current, making the thinner neutral cable overheat and catch fire.

Bottom line: if you want a generator set you can actually rely on, don't buy on price alone. Know what's inside the generator before you buy.