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AVR AVR (Self excited Automatic Voltage Regulators)

Stamford AVRs for self-excited generators without short-circuit maintenance receive their power direct from the generator output terminals, and control generator output voltage through continual automatic adjustment of the main rotor field strength





The SX460 is the standard AVR offered with generators in the lower power bands, achieving voltage regulation in the order of 1.5 %. A feature of this (and all Stamford AVR's) is that output voltage is reduced with speed below the normal operating level, to assist the engine or prime mover to recover after sudden application of a heavy load. This is an ideal choice for applications where a generator set is to be run in a stand-alone application where no specialist requirements exist.

 AS 440

The AS440 has all the features of the SX460, additionally achieving voltage regulation in the order of 1.0 %. A current transformer can be supplied with the AS440 to provide quadrature voltage droop for parallel operation with other generator sets, also a power factor control accessory can be fitted. The AS440 will also work with an auxiliary winding to support a short circuit and improve motor starting. A three phase sensing unit can be added to the AS440 AVR control system. The size of this AVR is ideal for mounting in the terminal boxes of the small (BC) Stamford generator ranges.


AVR-Stamfordmx321 AVR-AS440 AVR-Stamfordmx341


PMG AVR (Permanent Magnet Generator type Automatic Voltage Regulator)

For the ultimate in control, an AVR designed to operate with the Stamford Permanent Magnet Generator (PMG) system is often specified. In this design the AVR receives its power from a separately generated source, in the form of a small generator mounted on the end of the main generator shaft.

The advantage of this is that the AVR power source is not affected by sudden loads applied to the generator, hence the excitation field remains at full strength, sustaining a high level of short circuit current at the generator output terminals.

PMG AVR  Model  MX341

The MX341 achieves voltage regulation in the order of plus and minus 1.0 %, through the use of the PMG system. Protection against sustained over-excitation is standard on this AVR, as is a special engine relief load acceptance feature which enables full load to be applied in a single step.

PMG AVR  Model  MX321

The MX321 has all the features of the MX341, additionally achieving voltage regulation in the order of 0.5 %. There is also the facility for 3-phase RMS sensing, built in overvoltage protection and optional short circuit current level adjustment.
The combination of PMG providing an isolated power source and the MX321's RMS sensing makes an ideal arrangement for supplying the non-linear loads associated with UPS systems.