Datakom AVR-8 Alternator Voltage Regulator

An alternator voltage regulator that fits the terminal box

The AVR-8 is a Datakom electronic voltage regulator that lets an alternator produce a fixed output voltage. It has an open-chassis, resin-molded design intended to be mounted inside the alternator terminal box, and it contains no moving parts, so the datasheet describes it as able to work in highly vibrating environments. The regulator measures the phase-to-neutral or phase-to-phase voltage of the alternator and adjusts the DC voltage fed to the excitation winding until the desired voltage is reached. Datakom states that it is basically compatible with all brushless type alternators, which makes it a candidate replacement for a failed regulator once the excitation system has been checked. Find it with our other diesel generator spare parts.

Technical specifications

Protections and adjustments

The AVR-8 includes several protections that are listed in the datasheet: low-frequency protection, exciter over-current protection, high-temperature protection and sensing-loss protection. The low-frequency circuit reduces the output voltage in proportion to frequency below an adjustable threshold, which prevents damage when an engine is stopped under load, and the red LED shows when under-frequency protection is active. Sensing-loss protection terminates the excitation if there is no voltage at the sensing input, protecting the windings. An overload circuit limits the output current to its nominal value, preventing failure under overload or short circuit, and an optional adjustable overload limit is listed.

• VOLT potentiometer sets the generator voltage; terminals T1 and T2 are linked together when no external trimmer is used.
• STABILITY potentiometer sets the reaction speed so the regulator suits different alternators; turn anti-clockwise at no load until instability starts, then set slightly clockwise.
• FREQ potentiometer sets the under-frequency threshold; the nominal frequency changes between 50 and 60 Hz by a push-on link on the 60 HZ terminal.
• DROOP potentiometer and CT input S1-S2 allow parallel running; the factory preset gives a maximum 10% voltage droop at full load.
• Analogue input A1-A2 accepts a floating, isolated DC signal up to +/-3 V; a positive voltage on A2 increases excitation.

Selection and installation notes

Before ordering, confirm the alternator excitation system: the AVR-8 is a half-wave thyristor device for brushless alternators with excitation power taken directly from the generator terminals, so the sensing and power voltages must fit the 195-265 V-AC (L-N) or 340-450 V-AC (L-L) ranges, and the exciter must stay within 8 A continuous and 90 V-DC. Wiring terminals are P and N for the alternator input, P1 and P3 for sensing, T1 and T2 for the external trimmer, E+ and E- for the exciter field, S1 and S2 for the droop CT, A1 and A2 for the analogue input and the 60 HZ link. Datakom warns that the unit is for installation within other equipment by professional installers, that terminals and the heatsink may carry hazardous voltage, and that the voltage must not be raised above the alternator rated voltage.

Adjustment procedure: turn VOLT fully anti-clockwise, set any hand trimmer to midway, set STABILITY midway, connect a 0-300 V AC voltmeter, start the set at no load at nominal frequency, then carefully turn VOLT clockwise until rated voltage is reached. Residual voltage of at least 4 V-AC is needed for build-up.

Mechanical points from the datasheet: the unit is resin molded with an open chassis and a 37 mm height, and the wiring list shows eight terminal groups on the board. The thermal drift figure of 0.03% per degree C is quoted with the AVR heated to 70 C, and the regulation figure of +/-1% assumes 4% engine governing, so real-world voltage regulation also depends on the engine speed control. The analogue input must be fed only from a fully floating, galvanically isolated source because a non-isolated device could damage the equipment.

Selection and installation notes

An alternator voltage regulator is selected from the alternator excitation type, the excitation current and the voltage range. Check the wiring against the alternator terminal diagram, set the voltage and the stability adjustment with the set running without load, check the voltage under load changes and keep the regulator in a place where vibration and heat are moderate.

Information needed for a quotation

Send the full model code, the quantity, the delivery location in Oman or the GCC, the intended use and any accessories needed, so that the complete package can be quoted together.

Documents and supply information

The manufacturer data sheet is attached to this page and should be read together with the project specification and the site risk assessment before a purchase is confirmed. Ratings, standards and dimensions are quoted as printed on that sheet. Lead time, stock position and certificates available with the shipment are confirmed in the quotation, and we supply to Oman and the wider GCC region for industrial, utility and building services projects.

Documents and quotation

The Datakom datasheet for the AVR-8 is attached. Tell us the alternator make, model and exciter details with your request and we will quote; do not rely on this page alone to confirm compatibility with a specific alternator.