Hidden danger in autotransformer connection

摘要

The circuit shown in the November issue page 86 is very elegant.However,there is one very important warning which I was given over 30 years ago when I tried the same arrangement for work.If one of the primary leads comes adrift with the secondary still connected,then the voltage on the loose wire will be the voltage drop across the secondary winding multiplied by the turns ratio.This could be a very high voltage in the order of a thousand volts with a 20 to 1 turns ratio.