Stepdown Transformers

Published:2013/6/18 21:04:00 Author:muriel | Keyword: Stepdown Transformers | From:SeekIC

The step down transformer is the interface between the household Alternating Current system and the electronics that run your model railroad. The main purpose of the transformer is to reduce the relatively high voltage of the house to a safer and more practical voltage. There is also a secondary function that often goes un-noticed which is to provide electrical isolation between the household supply and the layout. This, in a properly constructed circuit, prevents the layout from being exposed to a dangerously high voltage if there is a fault on the primary side of the circuit. This isolation also separates the power supplies of each subsystem on the layout from the others. For example; On layouts with multiple DC throttles, each throttle is isolated from the others by its transformer. This allows common rail block wiring without causing a short circuit. The capacities of transformers are often given as a Volt/Ampere rating. This is the secondary voltage multiplied by the secondary current at full load and is roughly equivalent to a wattage rating but makes allowances for the peculiarities of alternating current. These allowances are not relevant to this page however. The secondaries of many transformers designed for low voltage applications are simply rated as secondary volts at full load amps. Note: The secondary voltage of a transformer is often significantly higher when there is no load than at full load. This is largely dependant on the the design of the transformer itself and is usually not a factor in model railroad circuits. However, in many low power and cheaply constructed transformers that are used in consumer electronics this voltage drop can be significant and must be taken into account when good regulation is needed. Transformers are generally, very efficient devices and no allowance is usually required for the small amount of heat that they may generate. It is good practice however to provide space around the transformer for air circulation and ventilation for enclosures. Power supply transformers should always be protected by a fuse on the primary side of the circuit. If a transformer supplies multiple loads, all loads should be be protected by individual fuses.



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