FS Class E656

Infobox Locomotive
name=FS class E656
electricsystem=3,000 V DC
tractionmotors=DC
powertype=Electric


caption=Unit E656.476 in XMPR livery.
builddate=1975-1989
builder=Officine Casaralta, Officine Reggiane, SOFER, TIBBcomponentistica Ercole Marelli, Ansaldo, Asgen, Italtrafo
weight=120 tons
uicclass=Bo-Bo-Bo
disposition=In service
numinclass=459
wheeldiameter=1.250 m
poweroutput= "continuous": 4,800 kW - "hourly": 4200 kW
tractiveeffort=249;kN
topspeed=150 km/h
length=18.290 m
width=3.000 m
height=3.800 m|
railroad=FS Trenitalia
nicknames= "Caimano" (Caiman)
safety=RSC4; SCMT

Infobox Locomotive
name=FS class E655
electricsystem=3,000 V DC
tractionmotors=DC
powertype=Electric

---

caption=E.655.505 in Terni in its original livery, July 2, 2006
uicclass=Bo-Bo-Bo
disposition=In service
tractiveeffort=300 kN
topspeed=120 km/h
railroad=FS Trenitalia
The Class E656 is an Italian articulated rheostatic-type electric locomotive built from 1973 to 1989. An evolution of the E646/5, they are all-purpose lomotives, and have been used on every kind of train, ranging from freight to intercity ones.

The E656 is nicknamed "Caimano" (Caiman).

Technique

The hull is divided in two parts, each one with its own two axles bogie, 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; futrher, 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 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.

eries

The 656 class is officially subdivided by FS into three series:

* 1st series (001 - 307)
* 2nd series (401 - 550)
* 3rd series (553 - 608)

The differences between series regard electrical and mechanical equipment.

The 600-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 ("Carrozza semipilota") or another Delfina-fitted locomotive.

Differences between locomotives can also be summed up as follows:

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:

* 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) 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 commanded manually, by default.

The driver selects the desired combination, which is automatically accomplished by an automatic system, which, through a particular array of logic gates and other components (capacitors, resistors, etc.), called "RAE" ("Relè Accelerazione Elettronico"), commands 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. present in the motors brings the current (which is read by transducers) 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 backward, when the current reaches high levels in respect of 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" ("Commutatore Escluditore Motori").

If rheostatic exclusion is needed to be commanded 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 position by position (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, similar to the ones employed on FS Class E444.

The rheostat is robust and dimensioned to stand high currents, however it cannot stand them for an excessive period of time, as there is the risk to melt it; the driver has to keep this in mind when driving. When temperature is too high (greater than 200 C°), the "VR" ("Ventilazione Reostato", Rheostat Fans) light starts to blink on the driver's console, in order 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.

ignificant 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.

See also

* FS Class E646/5
* FS Class E636