BASLER SSR32-12 Static AVR - Static Automatic Voltage Regulator for BASLER Alternators | OEM Replacement

BASLER SSR32-12. This is a Static Automatic Voltage Regulator from the BASLER range, supplied as a direct replacement for the same model number in the field. The figures that matter are printed in the table above and repeated here so the page can be read on its own: field current rating 12 Adc continuous, field resistance window 9-19 ohm depending on output, accuracy +/-0.5 per cent, working range -55 to +70 degC. Everything else on this page exists to explain how those four numbers decide whether the unit fits a particular alternator.

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. A regulator is a closed loop with a slow plant attached, and the plant is a large inductance. That is why the stability adjustment exists and why it is set after, not before, the voltage is correct.

Sensing. Single-phase or three-phase, NEMA voltage class. 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. The measurement that settles most arguments is the field current at full load, taken with a clamp meter, compared against the rating on the board.

Power stage and field drive. Power input 120 or 240 Vac, 50 / 60 Hz, output 32 Vdc on SSR32-12, 63 Vdc on SSR63-12, 125 Vdc on SSR125-12. Field current rating 12 Adc continuous, forcing capability Short-term forcing current available for load steps, field resistance window 9-19 ohm depending on output. 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. If the machine will not hold voltage at all, disconnect the field and measure the sensing voltage first. That one reading separates a sensing fault from a field fault.

Accuracy and response. +/-0.5 per cent steady-state accuracy, Better than 17 ms, 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. Field resistance is a temperature-dependent number. A reading taken on a cold morning and a reading taken after an hour at load are both correct and both different.

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. The cheapest diagnostic tool in excitation work is a DC ammeter in the field circuit. It turns a vague symptom into a number within seconds.

Paralleling. Reactive droop with cross-current compensated CT input. 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. On a machine that has been standing for months, check residual voltage before condemning anything: a winding that has lost its remanence will not build up on any regulator.

Protection built into the regulator. Over-excitation, integral fuse. 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. The cheapest diagnostic tool in excitation work is a DC ammeter in the field circuit. It turns a vague symptom into a number within seconds.

What it fits. Large frame alternators. Lifecycle status: In production as retrofit. 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. An alternator that has been rewound needs its field resistance re-measured, because a rewind commonly moves it by ten to twenty per cent in either direction.

Field notes on this model. The SSR series is the solid-state successor to the Basler SR: same terminal layout and same field current class, but a fully solid-state power stage instead of a magnetic amplifier. Basler sells an SSR Retrofit kit that mounts into the existing SR footprint with terminal-to-terminal wiring, so an old SR can be replaced in the field without drilling new mounting holes.

The retrofit case. Most SSR32-12 sales are retrofits, not new build. The machine is ten to twenty years old, the original board has failed, and the drawing is gone. In that situation the useful evidence is the exciter field resistance measured with a meter, the residual voltage measured at the AVR terminals with the machine turning at rated speed and no load, and the nameplate kVA. Those three readings will identify a compatible board even when the original part number cannot be found anywhere.

Earthing and shielding. The regulator reference is the machine frame. Bond the AVR mounting plate to the frame with a dedicated conductor rather than relying on the mounting screws, and earth the sensing cable shield at one end only. When a set shows a voltage that wanders slowly with no load change, the cause is usually a circulating current in the shield rather than a failing board.

Stability before accuracy. Set the stability adjustment until the voltage stops hunting on a load step, then leave it alone. Chasing the last tenth of a per cent of static accuracy by tightening stability is how a set ends up oscillating at 2 Hz under a resistive load and looking like a governor fault. The SSR32-12 is specified at +/-0.5 per cent; a real machine on a real load will not do better than that no matter how the trimmer is set.

The field resistance check. Measure the exciter field with the regulator disconnected and the machine stopped, then measure again after a run. Cold resistance is what the board sees at start-up; hot resistance is what it sees at full load. The SSR32-12 is specified with a minimum of 9-19 ohm depending on output voltage, and the real question is not whether the measured value is above that figure but whether the forcing current at that resistance still reaches the level the alternator needs to recover from a load step.

Hunting or slow oscillation. Oscillation at one to three seconds period is a stability setting problem. Oscillation at a fraction of a second is usually a sensing problem, often a bad connection that makes the reference jump. Distinguishing between the two by ear is possible and saves a lot of time.

Delivery and packing. Regulators are static-sensitive assemblies and should arrive in a sealed bag with foam, not loose in a box with a heatsink. Inspect on arrival and photograph the packaging before opening if there is any sign of crush damage.

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 SSR32-12 is rated for -55 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.

Fusing. Fit the fuse the manual specifies and nothing larger. A bigger fuse does not protect the regulator better, it protects it later. On a SSR32-12 the fuse is there to clear a field short before the thyristor is destroyed, and a 20 A fuse in place of an 8 A one turns a cheap board replacement into a rewind.