Automatic Voltage Regulators
When output drifts, will not build, or collapses under load, the regulator is the first thing to check after the excitation circuit itself.
Holding output voltage steady
An automatic voltage regulator senses alternator output and adjusts field excitation to hold voltage steady as load changes. When output drifts, will not build, or collapses under load, the AVR is the first thing to check after the excitation circuit itself.
We stock genuine Stamford AVRs — AS440, AS480, MX321 and MX341 — and DSE's own digital regulators, which add CAN communications and permanent magnet generator support where the installation needs a regulator that talks to the rest of the control system.
Match the AVR to the alternator frame, not just the part number on the failed unit: the Stamford units above each suit specific frame sizes, from the P0 and P1 to the S7.
Advantages of Genuine Stamford and DSE Regulators
The regulator is a small part of the set and the whole of its voltage quality. Genuine units, matched to the alternator frame, hold the output where the load needs it.
Matched to the frame
AS480 for P0 and P1, AS440 for S4 and HC5, MX321 for S6 and HC6, MX341 for S7, each with the excitation and sensing that frame calls for.
Regulation you can measure
Plus or minus 1% on the AS480, with under-frequency roll-off and over-voltage detection built in.
Digital where the panel needs it
The DSEA106 MKII and DSEA109 add stable digital regulation, and the DSEA109 brings CAN and PMG support into a DSE control system.
Key Features
- Genuine Stamford AS440, AS480, MX321 and MX341 regulators
- DSEA106 MKII and DSEA109 digital regulators, the DSEA109 with CAN and PMG support
- DSE815 RS485 interface for programming the DSE units
- Under-frequency roll-off and over-voltage detection on the AS480
Automatic Voltage Regulator FAQ
Match the frame size on the alternator nameplate, not the part number on the failed unit. The AS480 is the standard regulator on Stamford P0 and P1 frames. The AS440 is standard on the S4 and HC5 and an option on the UC22 and UC27. The MX321 is standard on the S6 and HC6 and an option across the Stamford range. The MX341 suits the S7. If the old regulator's part number does not appear here, send us that number and the nameplate and we will confirm the replacement.
A self-excited regulator such as the AS480 draws its power from the alternator's own output windings. A PMG-powered regulator such as the MX321 or MX341 takes its supply from a separate permanent magnet generator on the shaft, which isolates it from non-linear loads and gives better motor-starting performance and sustained short-circuit current. You cannot swap one type for the other without the matching excitation system on the alternator.
The MX321 senses all three phases, and the DSEA109 has 3-phase terminal sensing as well, so regulation stays steadier under an unbalanced load. The AS440, AS480 and MX341 are 2-phase sensing, which suits the frames they fit.
Fit a DSE digital unit when the installation needs the regulator to talk to the rest of the control system, or when an analogue regulator's temperature sensitivity is causing voltage drift. The DSEA106 MKII takes its supply from an auxiliary winding or a shunt system. The DSEA109 adds CAN communications and accepts PMG, auxiliary winding or shunt supply. You configure both in the DSE Configuration Suite, and the DSEA106 MKII needs the DSE815 interface for programming.
It is the RS485 interface between a DSE digital AVR and a PC running the DSE Configuration Suite. You need it to set up the DSEA106 MKII, and it is the programming route for the DSEA109.
The AVR is the first thing to check after the excitation circuit itself. Before replacing it, check the fuse or sensing supply to the regulator, the rotating diodes and, on a PMG machine, the PMG output. A regulator that has failed after a diode fault will fail again if the diodes are not replaced with it.
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