FS Class E.656

FS Class E.656
Company type	Electric locomotive
Industry	Rail transport
Founded	1975
Headquarters	Italy
Products	Electric locomotives

Template:Infobox locomotive

The Class E.656 represents an articulated rheostatic electric locomotive series from Italy, manufactured between 1975 and 1989. Developed as an advancement of the FS Class E.646, these locomotives are designed for mixed-traffic duties and have been deployed across a wide range of services, including both freight and intercity passenger trains.

This class is commonly referred to by the nickname "Caimano" (meaning Caiman).

Technical details

The locomotive's structure consists of two main sections, each supported by a twin-axle bogie, with an additional central bogie positioned between them. Each bogie is equipped with four DC traction motors rated at 400 kW (540 hp) each, resulting in a total of twelve motors.

Originally, the design targeted a maximum speed of 160 km/h (99 mph), but this was later adjusted to 150 km/h (93 mph) due to stability limitations; moreover, the locomotive's considerable weight prevented the adoption of rheostatic braking systems.

In recent years, numerous E.656 units have been reassigned to Trenitalia's Cargo Division for freight hauling purposes. To accommodate this role, their gear ratios were altered from 28/61 to 23/66, and their speed ceiling lowered to 120 km/h (75 mph). These modified locomotives are classified as Class E.655.

Series

FS officially categorizes the E.656 class into three distinct series:

First series (001 - 307)
Second series (401 - 550)
Third series (551 - 608)

Variations among these series primarily involve differences in electrical and mechanical components.

Locomotives belonging to the third series feature four field weakening shunts arranged in parallel and super-parallel motor configurations, whereas earlier series utilize three shunts. Additionally, third-series units are equipped with a 78-wire cable enabling remote operation from a control car (Carrozza semipilota) or another locomotive fitted with the Delfina system.

A summary of distinctions between individual locomotives is provided below:

Series	Units	Characteristics
1st	001 - 104	Motoalternators installed
2nd	201–251	Single static converter present
3rd	252–307	Motoalternators installed
4th	159–200	Single static converters (except unit 200)
5th	401–550	Equipped with two ARSA static converters
6th	551–608	Two ARSA static converters plus Delfina control system for remote command

Motors and Electrical System Overview

This locomotive is equipped with twelve 82/400 motors, each featuring class B insulation, arranged with four motors on each bogie.

The motor configurations mirror those used in the E.646 series, allowing the following connections:

Series: all motors connected sequentially, incorporating five shunts;
Series-Parallel: two groups of six motors in series, with five shunts;
Parallel: three parallel branches containing four motors each, utilizing three shunts (increased to four during the 6th series);
SuperParallel: four branches of three motors each in parallel, using three shunts (four on the 6th series);

Similar to earlier models, the E.656 employs a rheostat composed of 31 resistors divided into 21 packs, providing a total resistance of 17,015 ohm. This rheostat modulates the current supplied to the motors during startup and whenever transitioning between motor combinations by adjusting resistance levels. Unlike previous Italian locomotives, however, rheostatic exclusion is automated rather than manually controlled.

File:Banco E656.jpg

Driver console of an E.656; the lever in the middle is the combination selector.

The operator chooses the desired motor connection via a control lever, and an automatic system executes this selection. This system relies on a specialized network of logic gates and electronic components such as capacitors and resistors, collectively known as "RAE" (Relè Accelerazione Elettronico). The RAE manages a rotating mechanism called the avviatore automatico which controls transitions between motor configurations.

Through a potentiometer located at the driver's station, the maximum current for rheostat exclusion can be set. When the c.e.m.f. generated by the motors causes the current—monitored via transducers—to drop below this threshold, the avviatore progresses by closing rheostat contactors and bypassing resistors as speed increases until full exclusion is reached. Conversely, it can reverse if current levels rise excessively relative to speed.

Motor connection changes across different configurations are achieved by activating specific contactors. Transition management is handled by a device known as "CEM" (Commutatore Escluditore Motori).

For more precise rheostatic control—useful during coupling operations or when hauling heavy loads under low adhesion—the driver can operate the "PAC" (Pomello Avanzamento Comandato), a small lever that incrementally advances or retracts the avviatore automatico steps within the "Series" configuration only.

In locomotives classified as Third series, several functions traditionally performed by RAE, Avviatore Automatico, and CEM are integrated into an electronic control unit named Delfina, which is derived from technology used on FS Class E.444.

The rheostat is engineered to endure substantial currents; however, prolonged exposure to high current can cause overheating. Drivers must remain vigilant about this limitation during operation. Should the temperature exceed 200 °C or 392 °F, an indicator labeled "VR" (Ventilazione Reostato, Rheostat Fans) flashes on the driver's panel as a warning signal.

Auxiliary systems

The auxiliary systems consist of the following elements:

a pair of W242 compressors responsible for air generation;
an asynchronous three-phase motor rated at 17 kW, which drives four sets of motor cooling fans, seven sets dedicated to rheostat cooling, and two fans for the air conditioning within the cabin;
a 3 kVA transformer utilized for recharging the 24 V batteries, along with four additional transformers for cabin heating and one more for defrosting the windows.

Power supply methods vary by series:

first and third series employ two 125 kVA motoalternators powered by a 95 kW 3000 V motor with double collectors;
second and fourth series utilize a single static converter converting 3000 V DC to 450 V AC at 60 Hz, rated at 180 kVA;
fifth and sixth series are equipped with two static converters each, converting 3000 V DC to 450 V AC at 60 Hz, with a capacity of 120 kVA.

Motor cooling fans engage automatically once the reverser is shifted out of neutral, whereas rheostat cooling fans activate either upon the resistors reaching a temperature of 65 °C (149 °F) or manually via a dedicated control button operated by the driver.

Significant units

Unit E.655.200 was outfitted with two ARSA static converters for experimental testing.
Locomotives E.656.458 and E.656.468 are fitted with digital Octopus control systems, enabling remote operation of multiple locomotives from a single cab. These units also feature four weakening field shunts configured in Parallel and SuperParallel arrangements similar to those found in sixth-series models.

Accidents and incidents

File:E.655.403 - Giovinazzo.jpg

The E.655.403 (formerly E.656.403), involved in the Roma Casilina accident.

File:2009 Viareggio train accident surrounding damages 06.jpg

E.655.175, the locomotive involved in the Viareggio train derailment, shown the day after the incident.

On November 21, 1980, during the Curinga train disaster, units 075 and 280 were completely destroyed and subsequently scrapped in July 1983.
On March 14, 1995, near Chiusi-Città della Pieve, train E.656.542 failed to stop at a signal and collided with E.656.181.
On July 5 near Cuzzago, unit E.656.272 crashed into another train resulting in two fatalities and fifty-one injuries.
On August 20, 1996, close to Bologna San Ruffillo, E.656.225 derailed after entering a track that was closed, causing two injuries.
On August 2, 1997, near Roma Casilina, the traction hook of E.656.403 broke leading to derailment of one passenger car; four passengers sustained serious injuries. Excessive speed was determined as the cause—the train was traveling at 90 km/h instead of the permitted 30 km/h.
On June 4, 2000, near Solignano, a collision occurred between two freight trains resulting in four deaths and one injury.
On July 20, 2001, E.656.032 was completely destroyed in the Rometta Marea derailment.
On May 5, 2004, E.656.608 derailed near Libarna and collided with a freight train hauled by units E.655.511 and E.655.505.
On June 29, 2009, locomotive E.655.175 was pulling the freight train involved in the 2009 Viareggio train accident where it derailed and caught fire at Viareggio.

References

External links

Template:FS locos