Product Overview
Model. The LSA 47.2VS2 3-Phase is a Leroy Somer LSA 4-pole alternator. In Leroy Somer's LSA nomenclature 47.2 is the frame and VS2 is the core length: the frame fixes the stator bore and shaft centre height, and the core code fixes how much active iron is stacked into that bore. This one uses the very short core, stack position 2 within that family. A longer core in the same frame buys more output at the same temperature rise, which is why the same frame number appears across a spread of ratings. It is wound for three-phase service at 50 Hz. Electrical rating. At 0.8 power factor lagging this machine is rated 292 kW, which is 365 kVA, delivered as three-phase at 400 V 50 Hz. At 400 V line-to-line that is 526.8 A per line. This is the band where motor starting, not steady-state kW, usually sizes the machine: a direct-on-line motor of roughly 30% of the alternator kVA will pull the terminal voltage down by about 15% at start, which is normally acceptable, and anything larger needs a soft starter or a bigger frame. The 1500 rpm figure is synchronous speed, so there is no slip and no speed-dependent voltage droop. Frame and core. As built, this machine weighs 996 kg total, 387 kg rotor (VS2 core). The 47.2 family runs from the very short VS2 and VS3 cores at 996 kg through the S4 and S5 at 1126 kg, the M7 at 1253 kg, the M8 at 1302 kg and the L9 at 1392 kg. Rotor masses track the same order, from 387 kg on the VS cores to 547 kg on the L9. That progression is the physical reason the same frame number covers such a wide kVA spread. Stator resistance at 20 degrees C for this core is 0.0082 ohm line-to-neutral. The cooling circuit is direct air cooled, IC01, 0.9 m3/s at 47.2 frame, and the frame is steel frame with cast iron end shields. Three-phase winding. This is a three-phase machine with a 6 or 12 re-connectable winding brought out to 6 or 12 re-connectable terminals, so it can be reconnected on site for the usual voltage pairs β 380/220 V, 400/230 V, 415/240 V, 440/254 V and 480/277 V on the 50 Hz build, and the 60 Hz pairs on the 60 Hz build. Reconnection is done on the link board inside the terminal box, not by rewinding, which is why one machine can serve a 380 V job and a 480 V job. The 2/3 pitch design is what keeps the fifth and seventh space harmonics down without skewing the stator, and it is the reason the line-to-line waveform stays within the distortion limits the standards ask for. Four-pole build. A four-pole machine turns at 1500 rpm on 50 Hz and 1800 rpm on 60 Hz. That is the standard choice for generator sets from a few tens of kVA up to the low megawatt range, because the lower rotor speed gives a longer bearing life, a quieter fan, a higher subtransient reactance that is easier to coordinate with downstream protection, and a rotor that can carry a substantial damper cage for parallel operation. The trade is weight: a four-pole machine of a given kVA is roughly twice the mass of a two-pole one. Excitation and voltage regulation. The excitation system is SHUNT (R250) standard; AREP (R450 / D510C) or PMG optional, regulated by R250 shunt / R450 AREP / D510C AREP, holding steady-state voltage to +/-0.5%. Leroy Somer builds the LSA around three excitation levels. Plain SHUNT excitation with the R250 regulator is the default and is entirely adequate for a single set carrying a stable load. AREP β the Auxiliary winding, Regulated, Excitation, Protection arrangement, run through the R450 or D510C regulator β adds a separate auxiliary stator winding that keeps the excitation supply independent of the main output voltage, so the machine sustains about 300% of full load current into a short circuit for up to ten seconds. That is what lets a downstream breaker clear a fault selectively. PMG excitation goes one step further with a permanent magnet pilot exciter and is normally specified where the load is heavily non-linear or where the set has to ride through a sustained fault. Mechanical build. The frame is steel frame with cast iron end shields. Bearings are permanently lubricated ball bearings. Mounting is IM 1201 (single bearing, SAE flange + drive discs) or IM 1001 (two bearing, SAE flange + keyed shaft). Maximum overspeed is 2250 rpm, and the machine is rated for 1000 m without derating. The rotor is dynamically balanced to ISO 1940 and IEC 60034-14. The single-bearing arrangement couples through a SAE flange and drive discs, so the alternator rotor is carried partly by the engine flywheel housing; the two-bearing arrangement carries its own shaft extension and takes a conventional coupling. Where it fits. Factory and large commercial duty, plus marine auxiliary service. Loads include large induction motors, variable-speed drives, and rectifier front ends, all of which put harmonic current back into the alternator and make the winding pitch and the damper cage do real work. On a three-phase machine of 292 kW the practical constraint is usually the downstream protection and the cable, not the alternator itself. Core stack position. The VS2 core is stack position 1 of 6 in the LSA family, roughly 17% of the way along the family's lamination length range. It is the shortest stack the LSA family is built with. Short-stack builds like this one are picked when the set has to fit a compact canopy or a tight skid: the frame carries the rating with the least iron and the shortest overall length, at the cost of a slightly higher flux density in the teeth and a little more excitation current at part load. Where it sits in the range. The LSA family is catalogued from 6.4 kW up to 1680 kW, and this page covers the 292 kW / 365 kVA point. The step below it is the LSA 46.2VL12 3-Phase at 266 kW, 333 kVA. The step above it is the LSA 47.2S4 3-Phase at 328 kW, 410 kVA. If your load sits between two steps, take the higher one and let the engine run at part load rather than pushing the smaller machine to its limit on a hot afternoon. Reading the model code. A Leroy Somer designation is read as the LSA or TAL series, the frame size, and the core stack code (VS, S, M, L or VL plus a stack number). Here that gives LSA 47.2VS2 3-Phase for the model, 47.2 for the frame, VS2 for the core and three for the phase count, so the code on the nameplate and the code on this page match one for one. Quoting the full code rather than just the frame matters on this family, because the same frame number is built in several core lengths and the winding changes with the voltage. What the nameplate means once it is wired in. At 292 kW and 365 kVA this machine pushes 527 A down each line on a 400 V three-phase supply. That current, not the kVA figure, is what the switchgear and the cable have to survive, so the outgoing breaker should be a 800 A frame device set to trip above 659 A, and the run from the alternator terminals to the first panel should be 185 mm2 copper per phase for a normal 25 to 30 m span. Longer runs, aluminium conductors or tray-installed cable all move that number up, and the volt drop at full load is what decides it in the end. On the mechanical side the prime mover has to deliver about 327 kW at the coupling. The usual 1.10 to 1.15 margin over the alternator rating covers the fan, the excitation loss and the governor droop, and it is the reason a 292 kW alternator is normally quoted against a 327 kW engine rather than a 292 kW one. Fuel burn follows the electrical load almost linearly in this range. At a realistic 0.29 L per kWh for a modern common-rail set, running this alternator at full rating takes roughly 85 L per hour; at 75 per cent load it drops to about 66 L per hour and at half load to about 47 L per hour, because the fixed losses stay put while the variable ones fall away. Quote the breaker frame, the cable size and the engine rating together with the alternator, because a set that is right on paper and undersized on the cable is the most common way a good alternator gets blamed for a bad installation. Where this rating sits in the frame ladder. Within the 47.2 frame LSA carries 6 distinct ratings, and this is number 1 of them at 292 kW. This is the smallest rating the 47.2 frame carries; the step above is the LSA 47.2S4 3-Phase at 328 kW / 410 kVA, 36 kW over it. Every step inside one frame is one more lamination stack length. The shaft, the bearings, the foot pattern, the terminal box and the AVR are the same part across the whole ladder, and only the core length and the winding change. That is why the price gap between two neighbouring steps is small while the gap between the last step of one frame and the first step of the next is large. It also sets the value-engineering rule: dropping one core size inside the frame saves money and axial length but eats the margin to the load, while stepping up one size costs far less than jumping to the next frame and buying a bigger skid, a bigger breaker and a bigger cable with it. Supply. Supplied as a genuine Leroy Somer unit β Nidec Industrial Solutions, built in France. LSA and TAL ranges are built in Europe and carry a European certificate of origin. Each alternator ships with the routine test certificate, the winding connection diagram, and the AVR commissioning sheet. Export packing is seaworthy plywood on a pallet sized to the frame, and the machine is strapped and shrink-wrapped inside it. Tell us the engine make and model, the coupling arrangement (single or two bearing), the voltage and frequency, and whether you need a PMG, and we will confirm the build before it leaves the works.
