LEROY SOMER R130 Analogue AVR - Analogue Automatic Voltage Regulator for LEROY SOMER Alternators | OEM Replacement

What the R130 is. A Analogue Automatic Voltage Regulator built by LEROY SOMER for brushless excitation systems. On paper the specification is a list; in service it is a set of limits. The current the board will hold indefinitely is 2-4 A class; the field resistance window it will drive without exceeding its output voltage is Matched to the exciter field; the tightest voltage band it can maintain is +/-1.0 per cent; and the ambient range in which all of that remains true is -40 to +70 degC.

Excitation architecture. Self-excited, shunt fed. That single sentence decides most of the regulator's behaviour in a fault: whether the field survives a close-up short circuit, whether the machine builds up from residual voltage on its own, and how much the terminal voltage dips when a large motor starts on the same bus. Static accuracy is measured on a resistive load at constant frequency. Real loads and real governors are neither, so treat the figure as a comparison between boards rather than a promise.

Sensing. Single-phase sensing with voltage taps. The sensing circuit is the regulator's only view of the outside world, so its wiring matters as much as its specification. A voltage error introduced by a loose terminal or a long run of untwisted cable is indistinguishable, from the regulator's point of view, from a genuine voltage error on the alternator. Where a board has been superseded, the replacement usually fits the same footprint but not the same terminal numbering. Read the drawing, do not read the old wiring.

Power stage and field drive. Power input From the main stator, 50 / 60 Hz, output Up to 90 Vdc. Field current rating 2-4 A class, forcing capability Short-term forcing current available for load steps, field resistance window Matched to the exciter field. These are not independent numbers: the output voltage ceiling and the field resistance together set the maximum current the board can actually deliver, and the continuous rating is only reachable at the low end of the resistance window. A regulator rated for a minimum field resistance of a few ohms will not drive a high resistance field to full current, however good its specification looks on paper.

Accuracy and response. +/-1.0 per cent steady-state accuracy, Standard analogue response, thermal drift Low thermal drift. In practice the accuracy figure is the least interesting of the three. What an operator notices is recovery after a load step, which is governed by response and by available forcing current, and what a maintenance engineer notices after two years is drift, which is governed by the reference circuit and the ambient temperature inside the terminal box. Conformal coating is the difference between a board that survives a coastal site and one that corrodes quietly in eighteen months.

Frequency behaviour. Rated for 50 / 60 Hz, with Not published for this model - ask us for the nameplate data. The frequency-sensitive function exists to protect the prime mover, not the alternator: as engine speed falls the regulator reduces excitation so the alternator stops demanding torque the engine cannot supply. Without it, an overloaded engine is dragged down until it stalls, and the alternator is blamed for a fault that belongs to the fuel or governor system. Vibration kills more regulators than heat does. If a board has failed twice in the same machine, look at the mounting before looking at the supplier.

Paralleling. Reactive droop via CT. On a single set this circuit does nothing. On two or more sets it is the only thing that stops the machines from exchanging reactive power in a slow oscillation, and it is the first place to look when a parallel installation shows a circulating current that nobody can explain. Never flash a field through the regulator. Disconnect the board, flash the field directly, then reconnect. Flashing through the AVR is how a working board becomes a failed board.

Protection built into the regulator. Over-excitation protection. These functions protect the alternator and the regulator, not the installation. Downstream protection, loss of mains and reverse power all belong to the controller, and a site that relies on the AVR for them is a site that will eventually trip in a way nobody can explain. Never flash a field through the regulator. Disconnect the board, flash the field directly, then reconnect. Flashing through the AVR is how a working board becomes a failed board.

What it fits. Small and mid-size Leroy Somer alternators. Lifecycle status: Legacy or current depending on variant. Both halves of that sentence matter at order time. A board that fits perfectly but has been discontinued is a different commercial decision from one that fits and is in current production, and the price difference rarely reflects the difference in risk. Any AVR that has been in service for more than ten years is running on borrowed time, and the failure always happens at the least convenient moment.

Field notes on this model. This is one of the compact analogue regulators used on smaller Leroy Somer alternators and on older machines that predate the R438. Field current is modest, so it suits alternators up to a few hundred kVA. Because it is shunt fed, build-up depends on residual voltage, and a machine that has been standing for months may need to be flashed before it will excite.

Where this board earns its place. The R130 is normally the answer when a LEROY SOMER machine has lost regulation and the original board is either unavailable or priced like a small car. What decides the fit is not the brand name on the cover but three numbers: the field resistance window, the continuous field current, and the sensing voltage the machine actually delivers at the AVR terminals. Get those three right and the regulator behaves; get any one of them wrong and the symptom usually looks like a mechanical fault rather than an electrical one.

Documentation that survives the job. Photograph the terminal block before disconnecting anything, and write the sensing tap and the field resistance on the inside of the terminal box lid. Ten years later that note is the only thing that will let the next engineer choose a replacement without a full survey.

Commissioning sequence. Start with the machine at rated speed, no load, and the field disconnected. Confirm the sensing voltage at the AVR terminals is inside the window the board expects, then connect the field with the voltage trim at minimum. Bring the trim up slowly and watch the field current, not the terminal voltage, because the terminal voltage will look correct long before the field current has stabilised on a cold winding.

Why resistance matters more than current rating. A regulator delivers a voltage, and the field decides how much current that voltage produces. A board rated at 2-4 A class into a low resistance field will deliver far less into a high resistance one, because the output voltage is the limit. This is why an AVR that is electrically perfect on paper can fail to excite a particular alternator, and why the resistance figure belongs in the quotation rather than in the manual.

Voltage low under load only. This is the classic field current limit symptom. Measure the field current at full load and compare it with the 2-4 A class figure for the R130. If the board is at its limit, either the board is too small for the alternator or the field resistance has risen. A rewind, a corroded terminal or a long cable run will all produce the same reading.

Part numbers are not interchangeable across suffixes. On this family the suffix carries the field current class, the sensing arrangement or the frequency band, and two boards that look identical in a photograph can be a hundred per cent different in rating. Quote the full model number including the suffix, and where the suffix is unclear send a photograph of the original board with the terminal markings visible.

Standby versus prime power. A standby set runs a few hundred hours a year and its regulator spends most of its life cold; a prime power set runs continuously and its regulator spends its life at operating temperature. The R130 is rated for -40 to +70 degC, which is fine in both cases provided the terminal box has any ventilation at all. What changes between the two duties is the capacitor ageing inside the board, not the semiconductor, so a prime power machine should have the regulator inspected on a schedule rather than on failure.

Documentation that survives the job. Photograph the terminal block before disconnecting anything, and write the sensing tap and the field resistance on the inside of the terminal box lid. Ten years later that note is the only thing that will let the next engineer choose a replacement without a full survey.