Mechanical structure
The case of the generators for the series ET16 and ET20 is in aluminium; for all series, the covers are in die-cast aluminium. The shaft is in steel C45 and the rotor is in laminated steel with salient poles to improve the wave form. Self ventilation is obtained through fans splined on the shaft. The protection degree is IP23; upon request greater protection degrees may be supplied. The roller bearing is waterproof.

Operation
The internally produced and designed ASR regulator, provides a close voltage control controlling the generator excitation by means of brushes. The underfrequency protection, that can be set from the user, is avoinding possible troubles during the generator idling speed or start up.

Temporary voltage drops
The introduction of the rated voltage, starting from idle to rated speed, causes a temporary voltage drop lower than 9 %.

Response times
For a sudden introduction of the rated load under a constant speed, the voltage returns to the rated voltage in less than 0.1 seconds.

Overloads
The admitted overload is 300 % for 20 seconds, 50 % for 2 minutes and 10 % for one hour every 6 hours.

Radio interference
The series production meets all safety requirements included in 89/336 directive about electromagnetic compatibility and by class ,"G" and "N" of the VDE 0875 standard. Upon Customer's specific request it is possible to supply filters to meet stricter requirements such as MIL STD 461-462D, "K" class of VDE 0875, etc.

Special versions
The great flexibility of this series allows to arrange versions with special voltages e.g. direct current, allowing in a very reliable and economic way the performance of groups for battery charge.