Leroy-Somer Alternator
Spare Parts Supplier
Leroy-Somer, a brand of the Nidec group, builds the LSAM marine alternators and the LSA industrial range, which also goes to sea. A regulator, a diode bridge or a bearing is identified from the alternator plate and the type printed on the AVR in place, then offered as a genuine part or a checked alternative, confirmed before the quote.
Leroy-Somer alternators and regulators on board
On a ship, Leroy-Somer means the alternator on a generating set and the regulator that holds its voltage. The cards start with the two alternator ranges, then the two regulator families, then the excitation arrangement that links them and the rectifier parts on the rotor. A plate that reads STAMFORD, Newage or AvK belongs on the STAMFORD and AvK page.
LSAM
LSAM is the name Nidec uses for its Leroy-Somer marine alternators, and machines with LSAM plates also change hands in the used-equipment trade. Whatever follows the letters on the plate belongs to the type. Copy the whole line together with the serial number, because the spares are drawn up for that machine.
LSA 47.2 · LSA 49.3
LSA is the industrial range. Nidec notes that LSA machines also serve aboard ships next to their LSAM variants, and a marine spares trader lists the LSA 47.2 among ship alternators. Two examples are named here. Any LSA plate is read the same way, from the complete type line rather than the first figures.
R230 · R438 · R448 · R450
Four analogue regulator types that appear in Leroy-Somer documents and are sold by independent alternator-parts traders. Each is its own design with its own terminal layout. The quote follows the type printed on the regulator in place and the excitation arrangement of the alternator, and the wiring is compared with the machine's diagram before a unit is changed.
D350 · D550
Digital regulators that Nidec lists for LSA alternators, for SHUNT, AREP or PMG excitation. If the ship's machine already has one, the D type on its label and the alternator serial number are the basis of the quote. Where a D type is proposed in place of a fitted R type, the change is worked out from the alternator documents and written into the quote, never offered as a direct swap.
SHUNT · AREP · PMG
The three excitation arrangements Leroy-Somer alternators are built with. With AREP the regulator takes its supply from auxiliary windings in the stator, with PMG from a permanent magnet generator; SHUNT is the third arrangement. Which regulators can work on the alternator depends on it, so it is read from the alternator documents before any AVR is priced.
Rotating diode bridge and surge suppressor
The rotating rectifier on the rotor carries the diodes and a surge suppressor (varistor). Traders sell complete bridges, diode kits and single diodes under Leroy-Somer references, each kit listed for particular frames. A part is matched by the reference or type printed on it and by a photo of the bridge as fitted.
What brings a Leroy-Somer alternator into a request
Few of these requests are planned. Most follow an alarm on the switchboard, a failed start-up of the set or something found when the machine was opened, and the finding decides which lines go on the list.
New regulator, same fault
A new regulator only helps if the regulator was the fault. Before one is ordered, the electrician measures the excitation circuit, the regulator supply and the sensing wires, and those readings go into the request with the part list.
After a short circuit or a bad synchronisation
After such an event every diode and the varistor are tested, not only the part that is visibly burnt. The request then says whether single diodes or the complete bridge are wanted, and a photo of the bridge shows which kit layout the machine carries.
Damp machine after a long stop
An alternator that stood through a lay-up, or caught water from above, is megger tested before it runs again. The insulation resistance calculator turns the tester readings into PI and DAR values that can be sent with the request.
Voltage dips when a large motor starts
If the voltage sags each time a big pump or compressor starts, the question is whether the machine and its regulator suit that load. The motor current calculator works out the motor's current from its plate, a useful first figure for that discussion.
Leroy-Somer alternator parts we can quote
Every line below is tied to a label or a document: the alternator plate, the regulator, the part itself or the alternator parts list.
- Analogue R type and digital D type voltage regulators, by the type on the label
- Rotating diode bridges, diode kits and single diodes, by the reference on the part
- Surge suppressors (varistors) of the rotating rectifier
- PMG parts, on alternators built with a permanent magnet generator
- Current transformers of the regulation circuit, by their own label
- Bearings, by the bearing marking or the parts list item
- Space heaters and terminal box items, where fitted
- Air inlet filters, on machines that have them
What to send for a Leroy-Somer alternator
Two alternators with the same frame can be built for different excitation arrangements and carry different regulators. These items settle that before the first line is priced.
- A photo of the alternator nameplate with the type, serial number and frame
- The type on the AVR label, R or D series, and a photo of the regulator in place
- A photo of the AVR wiring terminals, taken before anything is disconnected
- The excitation arrangement (SHUNT, AREP or PMG) from the alternator manual or wiring diagram
- For diodes and varistors: the reference printed on the part and a photo of the rotating bridge
- Poles, frequency and speed as stamped; the motor speed calculator shows how they belong together
- The engine maker and type of the generating set, from the engine plate
Supply route review for Leroy-Somer alternators
Each line is reviewed as a genuine part or a checked alternative and confirmed before the quote. Regulators and rotating diode assemblies are matched by type, never by how they look.
Label type plus excitation arrangement
An AVR is matched on two points: the type on the label of the unit in place, and the excitation arrangement of the alternator taken from its documents. If either is missing, the question goes back to the ship before a regulator is offered.
Look-alike regulators exist
Boards from other makers are sold as compatible with, or as replacements for, R types, sometimes under the same type number. Nidec itself warns that parts which are not original can lead to premature failures. A photo of the label and the supplier's evidence for the unit offered are therefore checked before the quote.
Genuine part or a checked alternative
Regulators and rotating rectifier parts are quoted as genuine Leroy-Somer parts matched by type. Generic items such as bearings or air filters can go as a checked alternative where the buyer accepts it, with the marking compared and the route confirmed before the quote.
When the label shows an older type
Regulator types are replaced over the years. Where the fitted type has a successor, the new type and any wiring change are taken from the maker's documents and written into the quote, so the change is known before the unit reaches the ship.
Leroy-Somer alternators — questions buyers ask
Our regulator label says R450. Will any R450 do?
Only after two checks. The alternator's excitation arrangement has to match what the regulator is wired for, and the unit offered has to be the R450 its label claims, since compatible boards are also sold under that number. Send the label photo, a photo of the terminals and the alternator plate.
What is AREP, and why does it matter for the AVR?
AREP is one of the three excitation arrangements on Leroy-Somer alternators: the regulator takes its supply from auxiliary windings in the stator. The other two are PMG, with a permanent magnet generator, and SHUNT. The arrangement decides which regulators can be considered, so it is read from the alternator documents before a type is chosen.
Is an LSAM alternator the same machine as an LSA?
LSAM is the marine range and LSA the industrial one, and Nidec says LSA machines also serve aboard ships next to the LSAM variants. Whichever name the plate shows, parts are quoted against that complete type line and the serial number.
We only have the engine plate. Is that enough for alternator parts?
No. The alternator carries its own plate with its own type and serial number, and that plate decides the regulator, the diode bridge and the bearings. The engine plate still helps to identify the set.
Leroy-Somer also makes motors. Do you cover them here?
This page covers the alternators. For a Leroy-Somer motor, send the motor's own plate; the motor nameplate reader explains the fields on it.
Is Vessel Core connected to Leroy-Somer?
No, and there is no agreement of any kind. Vessel Core holds no distribution, representation or partnership agreement with Leroy-Somer, and quoting a component against one of its designations implies no approval by the maker and no claim of interchangeability.
Send the Leroy-Somer plate and the AVR label
With the alternator type, serial number, frame and the regulator type, the request is read against the right machine from the first line. If part of it is missing, send what you have and we will ask for the rest.
