Ripple on low voltage

IME, most miniature electric railways use either a live third rail for the positive with the earthed running rails for the negative return (like a miniature version of the Southern region main line electric railways) This system has the merit that the metalwork of the train is fairly reliably close to earth voltage and safe to touch by passerngers boarding/alighting.


Or alternatively they have the positive on one running rail and the negative on the other rail (like an enlarged model railway) This system requires special rolling stock with the wheels insulated from each other.  It is potentialy less safe since nothing prevents one side of the supply becoming earthed by leakage. If a fault on the train results in the metalwork becoming connected to the now live side of the supply, then anyone boarding/alighting is subjected to the full supply voltage between hands touching the train, and feet touching the ground. This can be dangerous even at very low voltages. Consider a sudden rain storm on a hot day when persons might go unshod. The risks may be much reduced if the train is largely of wooden construction, with metal door handles and the like mounted on timber rather than metal.


As an aside, the still extant Volks electric railway in Brighton originally used a nominal 50 volts DC supply between the running rails, but was later changed to a live rail with return via the earthed running rails. AFAIK it still uses 50 volts DC and the original rolling stock. It claims to be the oldest electric railway in the world.

IME, most miniature electric railways use either a live third rail for the positive with the earthed running rails for the negative return (like a miniature version of the Southern region main line electric railways) This system has the merit that the metalwork of the train is fairly reliably close to earth voltage and safe to touch by passerngers boarding/alighting.


Or alternatively they have the positive on one running rail and the negative on the other rail (like an enlarged model railway) This system requires special rolling stock with the wheels insulated from each other.  It is potentialy less safe since nothing prevents one side of the supply becoming earthed by leakage. If a fault on the train results in the metalwork becoming connected to the now live side of the supply, then anyone boarding/alighting is subjected to the full supply voltage between hands touching the train, and feet touching the ground. This can be dangerous even at very low voltages. Consider a sudden rain storm on a hot day when persons might go unshod. The risks may be much reduced if the train is largely of wooden construction, with metal door handles and the like mounted on timber rather than metal.


As an aside, the still extant Volks electric railway in Brighton originally used a nominal 50 volts DC supply between the running rails, but was later changed to a live rail with return via the earthed running rails. AFAIK it still uses 50 volts DC and the original rolling stock. It claims to be the oldest electric railway in the world.