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A Potted Coil Disclosure Number: IPCOM000035596D
Publication Date: 2005-Jan-26

Publishing Venue

The Prior Art Database


An electromagnetic apparatus such as an inductor, or a transformer, comprising a core with a centre leg between two side-legs where the coil encircles the centre leg and is embedded in a solid body.

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A potted coil


    This invention relates an electromagnetic apparatus such
as an inductor, or a transformer. In particular, the
invention relates to an electromagnetic apparatus
comprising a core with a centre leg between two side-legs.
The apparatus further comprising a coil encircling the
centre leg and being embedded in a solid body.

Background of the invention

    Transformers and similar inductive devices which comprise
a coil which is embedded in a potting material exist. The
potting material is normally provided to dampen vibrations
and to increase thermal conductivity between the apparatus
and ambient space.

    In US 6,392,519, a mounting apparatus is disclosed wherein
a transformer is arranged in a mounting cup. The cup is
sealed with a generally planar metallic plate forming a
heat sink, and the cavity between the cup and the plate is
filled with a polyurethane potting resin to provide
improved thermal transfer and resistance to vibrations.

The disclosed apparatus take up room and use of a separate
mounting cup increases the price of the finished electric

Description of the invention

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combination with the core a cavity with an inner surface
in contact with an outer surface of the solid body. Since
the body is surrounded by the core, it could be made by
moulding directly into a cavity formed by an inner wall of
the core, or alternatively, between a wall of a bobbin
arranged inside the core. Accordingly, the potting of the
coil is made without the use of an outer encapsulating
mould. The invention thus provides an apparatus which is
simpler and cheaper to manufacture and which has a reduced

    During manufacturing of the apparatus, the closure placed
in sealing contact with the core and thus forms a cup-
shaped sealed cavity within the core. The coil, e.g. fixed
to a bobbin is arranged inside this cavity. Subsequently,
the cavity is filled with a liquid potting material from
above. Since the material flows into the core in a liquid
state, all cavities and air-gaps inside the coil, e.g. air
gaps which may exist between the bobbin and a side wall of
the core is filled out with the potting material, and
after solidification of the material within the cavity,
the resulting solid body is in contact with the coil and
with the inner surface of the cavity and thus improves
thermal conductivity between the coil and the ambience.

    The body may form an uninterrupted heat conductive path
between the coil and an outer surface of the apparatus to
conduct heat from the coil through the body to the core or
to the closure without heat isolating air-gaps or similar
heat conductive obstructions. Since the body provides an
uninterrupted heat conductive path between the coil and
the core through the solid body, good heat conduction is
facilitated between the coil and the ambience.

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The core could be an EI core, e.g. laminated from sheets
of magnetically conductive and electrically isolated
plates. The coil could...