Toroidal transformers are
built around a ring-shaped core, which is made from a long strip
of silicon steel or permalloy wound into a coil, or from ferrite,
depending on frequency. This construction ensures that all the
grain boundaries are pointing in the optimum direction, making
the transformer more efficient by reducing the core's reluctance,
and eliminates the air gaps inherent in the construction of
an EI core. The cross-section of the ring is usually square
or rectangular, but more expensive cores with circular cross-sections
are also available. The primary and secondary coils are wound
concentrically to cover the entire surface of the core. This
minimises the length of wire needed, and also provides screening
to prevent the core's magnetic field from generating electromagnetic
interference.
Toroidal cores for use at frequencies up to
a few tens of kilohertz may also be made of ferrite material
to reduce losses. Such transformers are used in switch-mode
power supplies.
Toroidal transformers are more efficient (around
95%) than the cheaper laminated EI types. Other advantages,
compared to EI types, include smaller size (about half), lower
weight (about half), less mechanical hum (making them superior
in audio amplifiers), lower exterior magnetic field (about one
tenth), low off-load losses (making them more efficient in standby
circuits), single-bolt mounting, and more choice of shapes.
This last point means that, for a given power output, either
a wide, flat toroid or a tall, narrow one with the same electrical
properties can be chosen, depending on the space available.
The main disadvantage is higher cost.
A drawbacks of torodial transformer construction
is the higher cost of windings. As a consequence, toroidal transformers
are uncommon above ratings of a few kVA. Small distribution
transformers may achieve some of the benefits of a torodial
core by splitting it and forcing it open, then inserting a bobbin
containg primary and secondary windings.
When fitting a toroidal transformer, it is
important to avoid making an unintentional short-circuit through
the core (e.g. by carelessly fitting a steel mounting bolt through
the middle and fastening it to metalwork at both ends). This
would cause a large current to flow through the bolt, converting
all of the mains input power into heat, and blowing the input
fuse. To avoid this, only one end of the mounting bolt must
be fixed to the surrounding metalwork.
Dyco Electronics is a medium sized corporation
with a large, modern plant. Our toroidal
transformer production capabilities include processes that
assure that we are quick and efficient. Our customer service
staff will respond to your inquiries promptly and courteously.
Our materials, management and procurement personnel work hard
to insure that our costs are competitive.
To learn more about how we can provide the
toroidal transformers that will effectively meet your needs,
please contact us today:
Toroidal Transformers
Dyco ELectronics, Inc.
7775 Industrial Park Rd
Hornell NY 14843
607-324-2030
