FS Class E.656


The Class E.656 is an Italian articulated rheostatic-type electric locomotive built from 1975 to 1989. An evolution of the E.646, they are all-purpose locomotives, and have been used on every kind of train, ranging from freight to intercity passenger transport.
The E.656 is nicknamed "Caimano".

Technical details

The hull is divided in two parts, each one with its own twin axle bogie, plus a central bogie in the middle.
Each bogie mounts four DC motors, each providing, for a total of 12.
The initial project speed was, but later it was reduced to 150 due to stability problems; further, the heavy mass of the locomotive did not allow the use of rheostatic braking.
Recently, many E.656s have been transferred to the Cargo Division of Trenitalia to haul freight trains. The gear ratio has been reduced from 28/61 to 23/66, and the speed limit to. The modified units form the Class E.655.

Series

The E.656 class is officially subdivided by FS into three series:
The differences between series regard electrical and mechanical equipment.
The 3rd series locomotives have four field weakening shunts in parallel and super-parallel motor combinations, and the 78-wire cable to remote control the locomotive from a control car or another Delfina-fitted locomotive.
Differences between locomotives can also be summed up as follows:
SeriesUnitsFeatures
1st001 - 104Motoalternators
2nd201-251Single static converter
3rd252-307Motoalternators
4th159-200Single Static converters
5th401-5502 ARSA static converters
6th551-6082 ARSA static converters and Delfina control unit, for remote command.

Motors and electrical description

The locomotive has twelve 82/400 motors, with class B insulation, four per bogie.
They can be connected in the same combinations used on E.646:
Like their predecessors, E.656s have a rheostat that, by varying its resistance, gradually regulates the current to the motors on starts, and on each time a transition to the next combination is made; however, differently from older Italian types, rheostatic exclusion is not controlled manually, by default.
The driver selects the desired combination, which is automatically accomplished by a system which, through a particular array of logic gates and other components, called "RAE", controls a rotating device.
The driver selects the maximum exclusion current through a potentiometer on his desk, and the system, when the c.e.m.f. present in the motors brings the current to a value lower than the set current, makes the avviatore advance, closing the rheostat contactors as speed builds up, until it is totally excluded; similarly it may go backwards, when the current reaches high levels in relation to speed.
The different connections of the motors in the various combinations are accomplished by closing various contactors; their set-ups during transitions are handled by a device called "CEM".
If rheostatic exclusion is needed to be controlled finely, the driver can use the "PAC", a small lever that makes the "avviatore automatico" advance or go backwards step by step.
On Third series locomotives, many functions such as the ones of RAE, Avviatore Automatico, CEM, etc., are assumed by an electronic control unit derived from the ones employed on FS Class E.444.
The rheostat is robust and designed to stand high currents, however it cannot for an excessive period of time, as there is the risk of overheating; the driver has to keep this in mind when driving. When the temperature is too high, the "VR" light starts to blink on the driver's console to warn him.

Auxiliary systems

The following components form the auxiliary systems:
They are fed in various ways, depending on the series:
Motor cooling fans are automatically activated when the reverser is in non-neutral position, while rheostat fans activate when the temperature into the rheostat's resistors reaches 65 °C or they are manually activated by the driver via an apposite button.

Significant units