Reset Switches

This is your place to find answers to technical questions about electric cars of all sorts.  So....

The question came up recently on how the reset function works on our interurban cars, whether North Shore or CA&E.  Most of them have a reset/power switch ("canopy switch") located above the controller.  When in the center position, the control system is off; moving the handle to the right turns the controller on.  When moved to the left, it will reset the overload relay if tripped, and there's a spring return so the switch cannot be left in the reset position.  And you can reset only by turning the control system off.

Note that this reset switch should reset the overload relays on all cars in the train.  The way that works depends upon the particular type of control system.  Below is a simplified HL diagram for Westinghouse.  

In the center at top, the reset switch applies power either to the controller, or to line 8.  And line 8 is part of the control jumper, so it connects to all cars in the train.  Lower down and to the left, we see the reset coil for the overload relay, which is connected to line 8.  So that's pretty simple.

For cars with General Electric MU control, such as the CA&E steel cars, it's a little more complicated.  Here is the simplified diagram for C-165.  

In the upper right-hand corner, we see that the reset switch supplies 600V to either the controller or line 3.  And looking to the left, you can see that line 3 has connections to two circuits.  Contactor 4 is energized on all points, so whenever the motors are powered, line 3 will energize contactor 1 and provide some acceleration, its usual function.  But if the traction power is off, line 3 instead takes the lower path, and if the overload relay has tripped, the reset coil will be energized.  Again, this will affect all cars in the train.

Not all GE MU controls included this reset function, by the way.  The CA&E wood cars do not have overload relays, except for cars 319-321.  And there the reset switch is located inside the cabinet behind the motorman.  Now we have never found a wiring diagram for the 319-321, but I suspect that the reset function was not wired into the control circuits in the same way as the C-165.  And if I have some spare time, it shouldn't take long to verify that.  So if that's the case, even if the 319-321 were all in the same train, the overload relays would have to be reset from each car.

Any questions?