FS Class E656
The Class E656 is an Italian articulated
Articulated locomotive
Articulated locomotive usually means a steam locomotive with one or more engine units which can move independent of the main frame. This is done to allow a longer locomotive to negotiate tighter curves...

 rheostatic-type electric locomotive
Electric locomotive
An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...

 built from 1973 to 1989. An evolution of the E646/5
FS class E646
The FS E645 and E646 are two classes of similar electric locomotives used on Italian railways. They were introduced during the 1950s and they have been retired in 2009.- History :...

, they are all-purpose locomotives, and have been used on every kind of train, ranging from freight to intercity passenger trasport.

The E656 is nicknamed "Caimano" (Caiman).

Technical details

The hull is divided in two parts, each one with its own twin axle bogie
A bogie is a wheeled wagon or trolley. In mechanics terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage/car or locomotive, or sprung as in the suspension of a caterpillar...

, plus a central bogie in the middle.
Each bogie mounts four DC motors, each providing 400 kW, for a total of 12.

The initial project speed was 160 km/h, 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 E656s have been transferred to the Cargo Division of Trenitalia
Trenitalia is the primary train operator in Italy. Trenitalia is owned by Ferrovie dello Stato, itself owned by the Italian Government. It was created in 2000 following the EU directive on the deregulation of rail transport.-Passenger transport:...

 to haul freight trains. The gear ratio has been reduced from 28/61 to 23/66, and the speed limit to 120 km/h. The modified units form the E655 class.


The 656 class is officially subdivided by FS into three series:
  • 1st series (001 - 307)
  • 2nd series (401 - 550)
  • 3rd series (551 - 608)

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 (where the other series have three), and the 78-wire cable to remote control the locomotive from a control car
Control car (rail)
A control car is a generic term for a non-powered railroad vehicle that can control operation of a train from the end opposite to the position of the locomotive...

 (Carrozza semipilota) or another Delfina-fitted locomotive.

Differences between locomotives can also be summed up as follows:
Series Units Features
1st 001 - 104 Motoalternators
2nd 201-251 Single static converter
3rd 252-307 Motoalternators
4th 159-200 Single Static converters (except unit 200)
5th 401-550 2 ARSA static converters
6th 551-608 2 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 E646-5
FS class E646
The FS E645 and E646 are two classes of similar electric locomotives used on Italian railways. They were introduced during the 1950s and they have been retired in 2009.- History :...

  • Series: all motors are connected in series, five shunts;
  • Series-Parallel: two branches of six motors each, five shunts;
  • Parallel: three branches of four motors each, three shunts (four on 6th series);
  • SuperParallel: four branches of three motors each, three shunts (four on 6th series);

Like their predecessors, E656s have a rheostat (31 resistors subdivided in 21 packs, for a total resistance of 17,015 ohm
The ohm is the SI unit of electrical resistance, named after German physicist Georg Simon Ohm.- Definition :The ohm is defined as a resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere,...

) 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 gate
Logic gate
A logic gate is an idealized or physical device implementing a Boolean function, that is, it performs a logical operation on one or more logic inputs and produces a single logic output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and...

s and other components (capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...

s, resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...

s, etc.), called "RAE" (Relè
A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal , or where several circuits must be controlled...

 Accelerazione Elettronico), controls a rotating device (called avviatore automatico).
The driver selects the maximum exclusion current through a potentiometer on his desk, and the system, when the c.e.m.f.
Counter-electromotive force
The counter-electromotive force also known as back electromotive force is the voltage, or electromotive force, that pushes against the current which induces it. CEMF is caused by a changing electromagnetic field. It is the effect of Lenz's Law of electromagnetism...

 present in the motors brings the current (which is read by transducer
A transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...

s) to a value lower than the set current, makes the avviatore advance, closing the rheostat contactors (thus shunting the relative resistors) 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 contactor
A contactor is an electrically controlled switch used for switching a power circuit, similar to a relay except with higher current ratings. A contactor is controlled by a circuit which has a much lower power level than the switched circuit....

s; their set-ups during transitions are handled by a device called "CEM" (Commutatore Escluditore Motori").

If rheostatic exclusion is needed to be controled finely (e.g. on coupling maneuvers, or in case of a heavy train or poor adherence situations), the driver can use the "PAC" (Pomello Avanzamento Comandato), a small lever that makes the "avviatore automatico" advance or go backwards step by step (for "Series" combination only).

On Third series locomotives (official classification), many functions such as the ones of RAE, Avviatore Automatico, CEM, etc., are assumed by an electronic control unit (called Delfina) derived from the ones employed on FS Class E444
FS Class E444
The FS E444 is a class of Italian railways electric locomotives. They were introduced in the course of the 1960 until 1975. Starting from 1995, all E444s were upgraded as E444R.The locomotives are nicknamed Tartaruga .-E444 standard:...


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 (greater than 200 C°), the "VR" (Ventilazione Reostato, Rheostat Fans) light starts to blink on the driver's console to warn him.

Auxiliary systems

The following components form the auxiliary systems:
  • two W242 compressors used for air production;
  • an asynchronous 17 kW three-phase motor that is used to activate the four groups of motor-cooling fans, 7 groups for rheostat cooling and 2 fans for cabin air conditioning;
  • a 3 kVA transformer used to recharge the 24 V batteries, plus another four for cabin heating and another one for glass defrosters.

They are fed in various ways, depending on the series:
  • on 1st and 3rd series by two 125 kVA motoalternators, activated by a double-collector 95 kW 3000 V motor;
  • on 2nd and 4th series by a single 3000 V DC/450 V AC 60 Hz 180 kVA static converter;
  • on 5th and 6th series two 3000 V DC/450 V AC 60 Hz 120 kVA static converters.

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

  • Unit 200 had been fitted with two ARSA static converters for testing purposes.
  • Units 458 and 468 mount digital Octopus control units, which allow remote command of two or more locomotives from a single driving cabin. These units also have four weakenig field shunts in Parallel and SuperParallel combinations as sixth series' units.

Accidents and incidents

  • November 21, 1980 Curinga train disaster
    Curinga train disaster
    The Curinga train disaster, also known as the Lamezia Terme train disaster, was railway accident occurred on November 21 1980 between Curinga and Eccellente stations, in the Catanzaro province, Italy....

    : Units 075 and 280 are written off. Both scrapped in July 1983
  • 14 March 1995 near Chiusi
    Chiusi is a town and comune in province of Siena, Tuscany, Italy.-History:It was one of the more powerful among the Etruscan 12‑city confederation...

    -Città della Pieve
    Città della Pieve
    Città della Pieve is a comune in the Province of Perugia in the Italian region Umbria, located about southeast of Perugia. As of 31 December 2004, it had a population of 7,366 and an area of ....

     train E.656.542 missed a stop signal, crashing into E.656.181
  • 5 July near Cuzzago, E.656.232 impact against another train, causing 2 death and 51 injured.
  • 20 August 1996 near Bologna San Ruffillo E.656.225 derail into a closed rail, 2 injured.
  • 2 August 1997 near Roma Casilina, E.656.403 traction hook broke, causing derailment of its passenger car. Four were seriously injured. The accident was caused by velocity: the train was going at 90 km/h instead 30 km/h.
  • 4 June 2000 near Solignano
    Solignano is a comune in the Province of Parma in the Italian region Emilia-Romagna, located about 110 km west of Bologna and about 35 km southwest of Parma....

     a cargo train crush another cargo train, 4 death and 1 injured.
  • 20 July 2001, unit 032 was totaled in the Rometta Marea derailment
    Rometta Marea derailment
    The Rometta Marea derailment occurred on Saturday July 20, 2002, in Rometta Marea, part of the Rometta comune in Sicily, Italy.The Espresso 1932 Freccia della Laguna, a Ferrovie dello Stato train coming from Palermo to Messina, where it would join another convoy coming from Siracusa, derailed...

  • 29 June 2009, locomotive 655 175 was the locomotive hauling the freight train which derailed and caught fire at Viareggio
    Viareggio is a city and comune located in northern Tuscany, Italy, on the coast of the Tyrrhenian Sea. With a population of over 64,000 it is the main centre of the northern Tuscan Riviera known as Versilia, and the second largest city within the Province of Lucca.It is known as a seaside resort...


External links

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