70053K Datasheet, PDF (8/28 Pages) List of Unclassifed Manufacturers – THE ADVANTAGES AND BENEFITS OF USING AMVECO TOROIDAL TRANSFORMERS

TECHNICAL AND APPLICATION NOTES
The first toroid patent dates back to 1884. However, it’s
only during the past thirty years, as AMVECO and its pre-
deccesors developed practical manufacturing techniques,
that large numbers of toroids have been applied in wide
varieties of electrical and electronic products. The usage
of toroids has grown rapidly because of the many features
that permit new and innovative product designs. The
following is a discussion of various aspects of toroidal
transformer technology that will be useful to design engi-
neers contemplating their application in new or existing
equipment.
CUSTOM DESIGNS FOR OEM APPLICATIONS
Unlike their E-I counterparts, toroids lend themselves to custom applications
because toroidal designs don’t require the use of special costly tools, such as
stamping dies (required for special lamination forms).
Upwards of 95% of Amveco’s volume is consumed by custom products.
SMALL SIZE THROUGH REDUCED
CORE AND COPPER LOSSES
From Faraday’s equation for induced voltage in a transformer winding, we
derive the following practical equation:
Erms = 4.44 x f x N x B x A x 10^-8
Erms = Induced voltage in winding
f = Frequency (Hz)
N = Winding turns
B = Flux density
A = Core cross section (cm²)
Working flux densities of 12k to 14k Gauss are the practical limits for
typical laminated cores with airgaps. Thus, selecting a toroid may directly
reduce core material (weight) or winding turns (copper losses).
FLEXIBLE DIMENSIONS
As long as the cross sectional area of the toroidal core is held constant, the
height and diameter may be varied to meet the designer’s requirement.
The functional optimum diameter-to-height ratio is 2:1. For modern equip-
ment design emphasizing a low profile, a 3:1 ratio, wider diameter and
lower height may be more suitable. In cases where a smaller “footprint” is
desired, a 1.5:1 ratio should be considered (narrower diameter, higher
profile).
The only restrictions are those of the mechanical considerations of
insulation and winding machinery. A minimum center hole must be
maintained in order to permit the insertion of the winding machine
shuttle into the center hole of the core.
REDUCED SIZE REDUCTION THROUGH DUT Y CYCLE
A significant reduction in transformer size and weight may be realized in
many cases where the transformer is loaded intermittently. In such cases,
the load is energized for a small portion of the period. If the loaded
period is much shorter than the overall thermal time constant of the
transformer, the following equation applies:
Dutu Cycle Information
Increasing the working flux density will permit a lower number of turns
and/or a smaller cross sectional core area. Experience has shown that
working flux densities of 16k to 18k Gauss can be used in toroids.
Example: 750 VA load that is only utilized 15 seconds each minute.
Pnom = 750 15/60
Pnom = 750 .25
Pnom = 750 x .5
Pnom = 375VA
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