page_title: FS Class E.636
section_title: Motors and electrical description
hierarchical_section_title: FS Class E.636 / Technical details / Motors and electrical description
caption_attribution_description: Maniglione locomotiva E636
context_page_description: The FS E.636 is a class of Italian articulated electric locomotives. They were introduced in the course of the 1940s until the 1960s, and have been decommissioned since 2006. They have been one of the most numerous Italian locomotive group, and have been widely employed during their long career, hauling every type of train, ranging from freight to long range passenger services. Their introduction also saw the employment of some revolutionary design concepts, such as the articulated carbody and the three bogies scheme.
context_section_description: As most older Italian locomotives, E.636 has a rheostat (formed by 16 cast iron resistors connected in series, for a total resistance of 29 ohms) that needs to be gradually, but as soon as possible, excluded on start-ups, which regulates the current to the six 32R-200 DC traction motors, two per bogie.
  The motors can be connected in three combinations: series, series-parallel and parallel; each combination provides a progressively higher voltage to the motors, therefore increasing the current.
  Their set-up is the following:
  The rheostat (connected in series to the traction motors) is necessary because the DC motor has the intrinsic characteristic of absorbing a current inversely proportional to its rotating speed; at high speeds, it absorbs less current.  This means that on start the current would be very high, because the only resistance encountered would be only the one offered by motors and internal conductors, which is very low (a short circuit, in practice). The rheostat increases the overall resistance when starting the locomotive, lowering the current and allowing a smoother start.
  In S-P and P combinations, the rheostat is divided in three branches connected in parallel; this lowers the overall rheostat equivalent resistance to about 3.5 ohm, while in S combination its elements are all connected in series.
  Like almost every Italian locomotive with rheostatic regulation since E.626, traction is controlled via a lever (commonly referred to as maniglione) mounted on a support called roncola; this support has several notches, each representing a portion of the rheostat, plus three "end combination" notches and two "transition" positions (a bigger block between the notches).
  To accelerate, the driver rotates gradually counterclockwise the lever notch by notch, and in doing so the various rheostat contactors are closed, shunting the resistors and lowering the total rheostat resistance, also allowing more current to the motors; as speed builds up, the counter-electromotive force lowers this current, until the rheostat is no longer necessary: it is, then, totally excluded (obviously if in traction and in an "end combination" notch). This safely allows traction for an indefinite period of time, within certain limits.
  When the end combination notches are reached, the driver can then insert the single shunt (one for each combination) or make a transition to the next combination, reintroducing the rheostat which has to be excluded again, for the following combinations until the end of the parallel combination is reached. 
  The shunts increase the current into the motors by shunting some motor spires (through a contactor in parallel); this reduces the magnetic flux and, as said, increases the current (since the two are inversely proportional). There are various "shunt levels", depending on the locomotive, as is further explained; usually, there is one per combination. 
  It is also important to remove the shunts before making a transition, in order to avoid flashes due to abnormally high currents.
  Like some E.626s, E.636 locomotives are not provided with the "CEM" motor combiner (CEM stands for Combinatore Escluditore Motori), a device that, during transitions, rotates, combining the motors accordingly through various contactors.
  On E.636, this is achieved through the uses of more delicate spires, so transitions (especially backward ones) need to be very slow and gradual. The optimal moment to pass to the following/preceding combination first/last notches is when the motor ammeter indicates 0 Ampères, which happens when passing over the transition position with the lever (the driver should briefly stop in the middle of the block and pay attention to the ammeter), meaning that the motor contactors are in optimal position and is safe to proceed. Failure in doing this may result in flashes that will damage the contactors.
  An important parameter the driver has to consider, especially during rheostatic exclusion, is the current into the traction circuit.
  In particular, if he is excluding too fast, a wheel slippage can occur (in this 
caption: The traditional controller used on Italian rheostatic locomotives.
exif: {"Image ImageDescription": "", "Image Make": "NIKON", "Image Model": "E7600", "Image Orientation": "Horizontal (normal)", "Image XResolution": "300", "Image YResolution": "300", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "E7600v1.0", "Image DateTime": "2008:02:23 15:12:47", "Image WhitePoint": "[0, 0]", "Image PrimaryChromaticities": "[0, 0, 0, 0, 0, 0]", "Image YCbCrCoefficients": "[0, 0, 0]", "Image YCbCrPositioning": "Co-sited", "Image ReferenceBlackWhite": "[0, 0, 0, 0, 0, 0]", "Image ExifOffset": "482", "EXIF ExposureTime": "16639/1000000", "EXIF FNumber": "14/5", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "[50, 50]", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2008:02:23 15:12:47", "EXIF DateTimeDigitized": "2008:02:23 15:12:47", "EXIF CompressedBitsPerPixel": "3", "EXIF ShutterSpeedValue": "0", "EXIF ApertureValue": "0", "EXIF BrightnessValue": "0", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "3", "EXIF SubjectDistance": "0", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash fired, auto mode", "EXIF FocalLength": "39/5", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "3072", "EXIF ExifImageLength": "2304", "EXIF FocalPlaneXResolution": "0", "EXIF FocalPlaneYResolution": "0", "EXIF FocalPlaneResolutionUnit": "0", "EXIF ExposureIndex": "0", "EXIF SensingMethod": "0", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed"}