282PSL1704 3-Phase - Marathon | 18 kW

Model. The 282PSL1704 3-Phase is a Marathon PSL 4-pole alternator. Marathon reads the model as frame 282 followed by the PSL family code and the winding number 1704. The frame sets the mechanical envelope and the family code sets whether the machine is wound for single-phase or three-phase service. It is wound for three-phase service at 60 Hz. Electrical rating. At 0.8 power factor lagging this machine is rated 18 kW, which is 22.5 kVA, delivered as three-phase at 480 V 60 Hz. At 480 V line-to-line that is 27.1 A per line. Small frames like this are sensitive to load power factor: running them well below 0.8 PF pushes the field current up and the stator current up at the same kW, so the nameplate kVA is the number to design to. The 1800 rpm figure is synchronous speed, so there is no slip and no speed-dependent voltage droop. Frame and core. The 282 frame carries the 1704 core. Frame size fixes the stator bore and the shaft centre height; the core length fixes how much active iron sits in that bore, and therefore how much output the machine can make at a given temperature rise. The exact finished weight and outline drawing depend on the winding and the coupling, so they are confirmed on the certified datasheet issued with the order. Outline dimensions in inches: A 14.00 in | B 7.00 | BA 6.56 | C 18.50 (C w/PMG 23.10) | D 13.64 | E 6.25 | 2F 5.00 | H 8.00 | P 13.55 | X 18.56 | Y 8.93 | Z 3.42. The cooling circuit is direct air cooled, IC01, and the frame is rolled steel frame, cast iron end brackets. Three-phase winding. This is a three-phase machine with a 12 re-connectable winding brought out to 12 re-connectable terminals, so it can be reconnected on site for the usual voltage pairs — 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 self-excited brushless with SE350E AVR, regulated by SE350E standard / PM500 / DVR2400 with PMG, holding steady-state voltage to +/-1.0%. Marathon fits the SE350E as the standard regulator on the smaller frames, with the PM500 and the DVR2400 available where a PMG is specified. On the Mariner and harsh-duty builds the excitation stator is fully encapsulated and the rotating rectifier is a heavy-duty assembly with a 300% diode margin and sealed welded stud terminations, which is the difference between a machine that survives a damp boat hold and one that does not. Mechanical build. The frame is rolled steel frame, cast iron end brackets. Bearings are sealed for life ball bearings. Mounting is single bearing SAE flange or two bearing. Maximum overspeed is 2250 rpm, and the machine is rated for 1000 m. On the 280 to 430 frames the machine ships with twelve leads and a link board as standard, and the minimum inlet clearance is six inches. On the 570 frame and above the terminal box is mounted on top with the link board inside it, and a selenium surge suppressor is fitted as standard from the 360 frame up. Harsh-duty builds get multiple dip-and-bake cycles on the main stator. Where it fits. Small standby work: a shop till and lighting circuit, a telecom cabinet, a remote monitoring station, or a single-phase domestic changeover. At this size the alternator is usually the cheapest way to get clean power onto a load that the grid only abandons a few hours a year. On a three-phase machine of 18 kW the practical constraint is usually the downstream protection and the cable, not the alternator itself. Core stack position. The 1704 core is stack position 2 of 6 in the PSL family, roughly 33% of the way along the family's lamination length range. It sits between the shorter 1703 and the longer 1705. 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 PSL family is catalogued from 12 kW up to 225 kW, and this page covers the 18 kW / 22.5 kVA point. The step below it is the 282PSL1703l 3-Phase at 15 kW, 18.8 kVA. The step above it is the 282PSL1715 1-Phase at 20 kW, 25 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 Marathon designation is read as the frame number, the winding family (PSL, CSL, CSA, RSL, FSL or FDL), and a four-digit winding code. Here that gives 282PSL1704 3-Phase for the model, 282 for the frame, 1704 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. Frame position. The PSL range is built on 9 frame sizes — 281, 282, 283, 284, 285, 286, 287, 431, 432 — and the 282 frame is number 2 of them. No other frame in this range carries exactly this rating, so the 282 is the only build at 18 kW and there is no cross-frame decision to make. What the nameplate means once it is wired in. At 18 kW and 22.5 kVA this machine pushes 27 A down each line on a 480 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 63 A frame device set to trip above 34 A, and the run from the alternator terminals to the first panel should be 16 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 20.2 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 18 kW alternator is normally quoted against a 20.2 kW engine rather than a 18 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 5 L per hour; at 75 per cent load it drops to about 4 L per hour and at half load to about 3 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 282 frame PSL carries 4 distinct ratings, and this is number 2 of them at 18 kW. The step below is the 282PSL1714l 1-Phase at 15 kW / 18.8 kVA, 3 kW under this one; the step above is the 282PSL1715 1-Phase at 20 kW / 25 kVA, 2 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 Marathon unit — Regal Rexnord, built in United States. Marathon alternators are built by Regal Rexnord in the United States. 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.