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Transition Forestalling Switch.....what is it?
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<P>Thanks for the reply. Yes, it seems some of the early locos had manual trasition, at least that much is implied in the section from the GP7 manual below when referring to the transition <U>lever</U> . And manual transitioning seems in order when the loco had dynamic brakes......if I am reading this right. <P><FONT face="courier new,courier">106 <B>Transition Lever</B> The basic GP7L locomotive is not equipped with a transition lever. There are, however, certain types of the GP7 that are equipped with transition levers, even though transition (forward and backward) is fully automatic on the GP7 locomotive. The inclusion of such a lever is principally for use with dynamic brakes, or for the purpose of providing a means for effecting manual transition in other type units (not equipped with automatic transition) when such a unit is being used in multiple unit operation with a GP7. Thus, the transition lever has 5 positions: OFF, 1, 2, 3 and 4; if the locomotive is equipped with dynamic brakes, an additional position "B " (braking range) is also included. </FONT> <P><FONT face="courier new,courier">Earlier production GP7 locomotives that were equipped with transition levers had this lever arranged to control the Road-Service feature. On those locomotives, the placing of the transition lever in the OFF position caused the locomotive to start with the "teaser" type of starting; placing the transition lever in the #1 position caused modified maximum field starting to be obtained. Present production locomotives, however, have a toggle switch (located on the side of the controller) to control the Road-Service feature, see Art. 108. Thus, the controller on the GP7 has mechanical interlocking of the levers identical to that found on "F" type locomotives, see Art. 109. </FONT> <P><FONT face="courier new,courier">107 <B>Transition Forestalling Switch</B> This switch is located on the engineman's control panel and is used to forestall an undesired forward transition. </FONT> <P><FONT face="courier new,courier">When the switch is in the "UP-AUTO" position, forward transition will take place automatically at the proper time. </FONT> <P><FONT face="courier new,courier">When forward transition is not desired, the switch is placed in the "DOWN-SERIES" position. Traction motor connections will then stay in series load parallel, regardless of locomotive speed, generator voltage or position of regulator arm, Fig. 1-6. </FONT> <P><FONT face="courier new,courier">The transition forestalling switch should not be moved from the "SERIES" to the "AUTO" position unless the throttle is in the 6th position, or lower. However, if the speed of the locomotive is below the forward transition speed, it is permissible to move the switch to the "AUTO" position with full throttle operation. This will prevent any possibility of forward transition taking place at an excessively high voltage. </FONT> <P><FONT face="courier new,courier">Movement of the switch from the "AUTO" to the "SERIES" position may be done at any time, as this will not cause backward transition to take place. Backward transition is determined only by the operation of the backward transition relay, or by reducing the throttle to the "Idle " position. </FONT> <P><FONT face="courier new,courier">The operation of the transition forestalling switch is not trainlined. In multiple unit operation, the forestalling switch in each unit must be placed in the position in which it is desired to operate the locomotive. </FONT></P> <P><FONT face="Courier New"></FONT> </P> <P><FONT face=arial,helvetica,sans-serif>My next and related question is about the series-parallel and variation of that connection that the engineer had option to select.</FONT></P>
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