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Re: Do Electronic Ballasts have Coils

Jerry Baker asked if Electronic Ballasts like the IceCaps have coils or

Generally speaking, because true electronic ballast contain inverters
(that is, a device that increases the frequency of the alternating
current) and operate at a higher frequency than normal ballasts, a much
smaller coil can be used as a ballast or choke to impede the flow of

The engineers will have a field day with this simplified explanation,
but I think it carries the basic ideas.  A flourescent bulb will take
all the current you give it until it burns up.  One of the purposes of
a ballast, of any type, is to impede the flow of current that a
fluoreescent bulb receives.  Coils of wire that have an alternating
current running through them have an inductive field that is
created/collapsed/created/collapsed each time the current alternates. 
The large the coil, the stronger the magnetic field (more Henries --
that's a measure of induction or the strength of an electromagnetic
coil when current is running through it).  This change in the induction
or magnetic field impedes the flow of current through the coil. The
higher the frequency of an alternating current, the fewer Henries  are
needed to impede the flow.  So at 60 hertz a much larger coil is needed
than at the 27kHz of an IceCap -- I think it's 27 kHz -- somewhere
around there anyway.  

The impedance could be acheived without a coil, in principle, but it's
more expensive and, for practical purposes, unnecessary.

So expect electronic ballasts for a given type and size of bulb to have
coils, but expect them to be much smaller than those in conventional
ballasts that operate the same type and size of bulb.

Scott H.

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