Leroy Somer AVR R448


For both AREP & PMG excitation systems,the alternator voltage regulator is the R 448. With AREP excitation, the R 448 electronic AVR is powered by two auxiliary windings which are independent of the voltage equal circuit. The primary winding has a voltage in ratio to that of the alternator (characteristic Shunt), the next has a voltage in proportion to the stator current (compound characteristic: Booster effect).The power supply voltage is rectified and filtered before being used by the AVR monitoring transistor. With PMG excitation, a permanent magnet generator (PMG) added to the alternator supplies the AVR with voltage which is free of the main alternator winding. This is built-in at the rear of the machine and connected to the R 448 AVR, and the ST9 jumper must be disconnected. These two principles provide the machine with a short-circuit current capacity of 3 IN for 10 s, and good protection to distortions generated by the load. The AVR monitors and corrects the alternator output voltage by adjusting the excitation current. In SHUNT excitation, R 448 supplied by main windings (140V – 50/60 Hz) to X1, X2.
On application of a load, the rotation speed of the generator set decreases. When it passes below the preset frequency threshold the LAM causes the voltage to drop by approximately 13% or 25% and consequently the quantity of active load applied is reduced by approximately 25% to 45%, until the speed reaches its rated value again. Hence the LAM can be used either to reduce the speed variation (frequency) and its duration for a given applied load, or to increase the applied load probable for one speed variation (turbo-charged engine).

To avoid voltage oscillations, the trip threshold for the LAM function should be set approximately 2 Hz below the lowest frequency in steady state. It is advisable to use the LAM at 25% for load impacts Š 70% of the genset rated power.LAM, action eliminated by cutting the ST5 jumper. During load impacts, the function helps the genset to return to its rated speed faster thanks to a gradual increase in voltage according to the principle:

> If the speed drops between 46 and 50 Hz, the rated voltage follows a fast gradient as it is restored.

> If the speed drops below 46 Hz, since the engine needs more help, the voltage follows a slow gradient as it returns to the reference value.

The new functions of the R448 are :
– Parallel operation between alternators with C.T.
– Parallel operation with the mains with C.T.and R 726 module
– 3-phase sensing (R 731 module)
– LAM function integrated in the R 448 AVR.

4 in stock

Categories: , Tags: , ,



  • Leroy Somer have stopped manufacturing the LS branded R448 AVRs in France and they have superseded the R448 with the R450. 
  • To maintain supply of new AVRs for our customers, we now manufacture the R448 AVR without the LS Logo.


There are no reviews yet.

Be the first to review “Leroy Somer AVR R448”
Review now to get coupon!

Your email address will not be published. Required fields are marked *