331CSA-B3018 1-Phase - Marathon | 9 kW

Model. The 331CSA-B3018 1-Phase is a Marathon CSA 4-pole alternator. Marathon reads the model as frame 331 followed by the CSA family code and the winding number B3018. 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 9 kW, which is 11.2 kVA, delivered as single-phase at 240 V 60 Hz. At 240 V that is 46.9 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 331 frame carries the B3018 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 capacitor start, 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 single-phase machine of 9 kW the practical constraint is usually the downstream protection and the cable, not the alternator itself. Core stack position. This build carries winding code B3018 on the 331 frame. Winding numbers in this family are assigned per frame and per voltage, so B3018 fixes the turns per coil, the conductor section and the parallel paths for this rating. Where it sits in the range. The CSA family is catalogued from 11 kW up to 23 kW, and this page covers the 9 kW / 11.2 kVA point. The step above it is the 332CSA-B3020 1-Phase at 11 kW, 13.8 kVA. It is the smallest build in the family, so it is the one to quote when the load is fixed and the budget is tight. 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 331CSA-B3018 1-Phase for the model, 331 for the frame, B3018 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 CSA range is built on 4 frame sizes — 331, 332, 333, 334 — and the 331 frame is number 1 of them. No other frame in this range carries exactly this rating, so the 331 is the only build at 9 kW and there is no cross-frame decision to make. What the nameplate means once it is wired in. At 9 kW and 11.2 kVA this machine pushes 47 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 63 A frame device set to trip above 59 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 10.1 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 9 kW alternator is normally quoted against a 10.1 kW engine rather than a 9 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 3 L per hour; at 75 per cent load it drops to about 2 L per hour and at half load to about 1 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. 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.