Versatile Application
The application of toroidal power transformers is similar to that of
stacked lamination type transformers. Most traditional circuits and
calculations for rectification and filtering apply. Toroidal transformers
can be designed in many sizes with a variety of secondary and primary
windings, special electrostatic shielding, stray field protection, and
mounting configurations.
What's Special About Toroids?
The core
of the toroidal transformer is made of a grain-oriented silicon steel strip
wound under controlled tension into a "donut." It is mechanically very solid
and stable. Because of the way primaries and secondaries are wound uniformly
around the core and the fact that toroids have no air gaps, there is very
low emission of stray magnetic fields or EMR (Electro-Magnetic Radiation).
• Smaller
Size and Weight
Toroid's higher efficiency than laminated type transformers can
save up to 50% in weight and size. This helps simplify the design of cabinets,
mechanical geometry, and mounting configuration. It suits the trend for smaller,
more compact electrical and electronic products.
The diameter-to-height ratio of a toroid can easily be varied (as
long as area of the cross section is held constant) to suit the mechanical
design. This is great for low profile equipment.
• Low Operating Temperature
Operating temperature is an important safety factor. Our toroidal transformers,
built for Class A (105C) or Class B (130C) operation, are normally calculated
for a temperature rise of 40-50ºC. If lower temperature is needed, a larger core
can be used. When the transformer is operating at half its load, the temperature
rise is only 1/4 of the rise at full power.
Low Stray Magnetic Fields
Toroids emit very low radiated electro-magnetic fields, typically
1/8 the level of the conventional E/I lamination type. For most applications no
special shielding is needed. This suits toroidal power transformers for
applications in sensitive electronic equipment, such as low level amplifiers,
medical equipment. When further reduction of the EMR is needed, a magnetic
shield around the circumference of the transformer can be provided.
Encapsulation in a steel can further reduces hum and adds a cosmetic benefit.
• Low Mechanical Noise (Hum)
The uniform windings enveloping the core greatly reduce
magnetostriction - the main source of the familiar "hum" found in conventional
laminated transformers. Compared to those models, our toroidal power transformer
is silent. This makes ours ideal for hospital and office environments, where an
annoying hum would be unacceptable.
• Electrical Efficiency
There are two important reasons why a toroidal transformer is more
efficient than the stacked E/I lamination type. One is that the high quality
grain oriented steel is utilized at close to 100% in all areas of the core. As a
result the core may operate at 15-16 kilogauss versus 12 to 14 kilogauss in the
E/I design. There are no air gaps in the core, which means a no-load current
draw of about 10% of that of a stacked lamination construction. The other reason
is that the windings are distributed over the entire core circumference which
reduces the mean length of copper wire per turn in comparison with the E/I
transformer, the windings on which are located only on parts of its steel core.
Accordingly, a toroidal design requires less steel and copper wire with less
core and copper losses resulting in energy savings.
• Reduced No-Load Losses
Compared to l E/I transformers, toroidal power transformers
exhibit extremely low no-load losses. In applications where a circuit sits in a
"stand-by" mode for long periods, the energy cost savings can be significant.
Lower operating temperature may also be beneficial.
• Voltage Regulation
The voltage drop under load (regulation) is much lower than that
of a conventional transformer. Increasing the core size can further reduce
voltage drop.
• Easy to Mount
A single center screw quickly and easily mounts a toroidal
transformer. Compared to laminated transformer mounting, this cuts down on parts
as well as assembly time in your product.
The Bridgeport Magnetics Advantage