4.3 Reliability

Therefore, this chapter is even shorter than the previous one. The ballast itself hardly ever becomes damaged through surges or overvoltages because of its simple and sturdy structure and because it has to be designed to withstand its own self-induction pulse anyway. Surely it happens that a magnetic ballast fails on account of shorted turns in the winding, which produce excess heat and thereby further turn shortings, then current increase, even more excess heat and so on. It may take some weeks, however, before this process reaches this avalanche state and finally blows the fuse. By then the fault may have been detected because of charred smell or uncommon noises but in any case the ballast (and the adjacent lamp which is overloaded by the excess current) will under no conditions cause a fire during failure. This is the only type of failure that ever occurs with magnetic ballasts, and it is really the exception.