286PSL1712 1-Phase - Marathon | 55 kW

Model. The 286PSL1712 1-Phase is a Marathon PSL 4-pole alternator. Marathon reads the model as frame 286 followed by the PSL family code and the winding number 1712. 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 single-phase service at 60 Hz. Electrical rating. At 0.8 power factor lagging this machine is rated 55 kW, which is 68.8 kVA, delivered as single-phase at 240 V 60 Hz. At 240 V that is 286.5 A through the line and the neutral. 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 286 frame carries the 1712 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. The cooling circuit is direct air cooled, IC01, and the frame is rolled steel frame, cast iron end brackets. Single-phase winding. This is a single-phase machine, so the winding is laid out to produce one sinusoid across the output terminals rather than a three-phase set. Single-phase alternators of this size are almost always fitted with a capacitor or a compounded excitation arrangement to hold the voltage steady as the load swings, because the pulsating armature reaction of a single-phase load pulls the terminal voltage around far more than a balanced three-phase load does. The practical consequence for the buyer is that single-phase kVA and three-phase kVA of the same frame are not interchangeable: the single-phase machine is derated for the same iron, and the wiring, the circuit breaker and the cable all have to be sized on the single-phase current, which is roughly 1.7 times the three-phase current for the same kVA at the same voltage. 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. Commercial buildings and small industrial plants: office air conditioning, refrigeration, lifts, and a workshop full of induction motors. Motor starting is normally the sizing case rather than steady-state kW. On a single-phase machine of 55 kW the practical constraint is usually the downstream protection and the cable, not the alternator itself. Core stack position. The 1712 core is stack position 2 of 2 in the PSL family, roughly 100% of the way along the family's lamination length range. It is the longest stack the PSL family is built with. Long-stack builds carry the rating in the frame with the lowest flux density of the family. The extra iron costs length and weight, and buys a cooler-running core, lower magnetising current, better part-load efficiency and more margin for site ambient above 40 C or for a non-standard voltage. Where it sits in the range. The PSL family is catalogued from 12 kW up to 225 kW, and this page covers the 55 kW / 68.8 kVA point. The step below it is the 285PSL1700 3-Phase at 50 kW, 62.5 kVA. The step above it is the 287PSL1713 1-Phase at 60 kW, 75 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 286PSL1712 1-Phase for the model, 286 for the frame, 1712 for the core and single 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 286 frame is number 6 of them. No other frame in this range carries exactly this rating, so the 286 is the only build at 55 kW and there is no cross-frame decision to make. What the nameplate means once it is wired in. At 55 kW and 68.8 kVA this machine pushes 286 A down each line on a 240 V single-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 400 A frame device set to trip above 358 A, and the run from the alternator terminals to the first panel should be 120 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 61.6 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 55 kW alternator is normally quoted against a 61.6 kW engine rather than a 55 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 16 L per hour; at 75 per cent load it drops to about 12 L per hour and at half load to about 9 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 286 frame PSL carries 2 distinct ratings, and this is number 1 of them at 55 kW. This is the smallest rating the 286 frame carries; the step above is the 286PSL1701 3-Phase at 60 kW / 75 kVA, 5 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.