The above diagram shows the main 1500v connections in a typical 2 motor 3000 series "red" car. Switches F3 and F4 are no longer used, and switches F1 and F2 are permanently wired closed, effectively disabling the weak field notch on these cars. This was done in the 1970s firstly because of a shortage of spare parts for switches (deleting them yielded four spares per car in the fleet), and also to reduce stress in the field windings of the older MV172 motors. Unfortunately for speed freaks the HET Electrical Engineer has decreed that things will stay this way for "2 motor" cars however 4 motor cars such as C7396 will eventually have weak fields restored.
Above : The 36vDC control circuit for a 1927 type "red" car. As noted above, the steps for "WF" (Weak field) and switches F3 and F4 are now deleted.
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