FS Class ALe 642
FS ALe 642 is a class of Italian Electric Multiple Unit trains built at the beginning of the 1990s for use on secondary lines and for commuter traffic. Currently all units of this group are assigned to Emilia Romagna and Tuscany regional service divisions (DTR, "Direzione Trasporto Regionale"). Description. This class is strictly derived from the previous ALe 582 and ALe 724 EMUs, sharing most of the mechanical and technical characteristics. The main differences are in the electrical part (especially traction control and low tension circuitry) and for the presence of 2nd class only seatings. The  frontal part containing cabins consists of a preformed structure made of polyester reinforced with fiberglass. They originally had the "Navetta" livery, painted in gray with orange and red lateral stripes; now they all have received the usual green-white XMPR livery. Technical description. Units arrangement. Like the previous EMUs on which they are based on, Class 642 can be divided in one or more sections containing a varying number of elements: Each section must contain at least one ALe and one Le, with a driving cabin on each end; a train can be formed by a maximum of two sections  coupled with Scharfenberg type automatic coupler. Basic section arrangement are: where M are ALe 642, R Le 764 and Rp Le 682. Electrical description. Engine units employ four direct current traction motors placed inside the bogies, two for each one of them. They are fed by choppers, one per bogie; unlike ALe 724, where the regulation is shunt-chopper type and a resistor is used when accelerating at low speeds, a full-chopper system is used as on ALe 582 with the only difference that in this case we have three frequency choppers (582 employ single frequency ones). Chopper regulation  allows rheostatic braking (active above/until , about if also using pneumatic braking) and the current generated by motors can be sent to the overhead supply line if there are other trains able to absorb it. An interlocking valve limits to 0.4 bars the pressure into the brake cylinders of the ALes when electrically braking. Low tension circuitry employs 24 V batteries (110 V on ALe 724 and ALe 582) recharged by 380 V three-phase 70 kVA DC/AC static converters, located on engine units and Le 682 and which supply electric current to auxiliary services. FS Class ALe 642