The standard range of toroidal transformers has been designed to enable an engineer to choose an "off the shelf" product for prototype work with the confidence that bulk production quality will be maintained.

The range has been carefully selected from voltages and ratings widely used in todays modern electronics world.  However, if the range does not meet your requirements our design team will be pleased to produce special types against your specifications.


Compared to the conventional transformer, the toroidal transformer has superior shape as it requires less material (Typically it is 50% smaller and lighter). The copper wire is spread over the entire core and therefore the length of the winding is shorter.  This results in a stacking factor of 95% of its theoretical weight. The direction of the magnetic flux of the entire core is the same as the rolling direction of the steel.  A high flux density, therefore, can be allowed with further material saving as a result.  The absence of an air gap typically provides an 8:1 reduction of induced noise. In addition, the windings enveloping the core effectively reduce magnetostriction, the main source of hum found in standard vertically laminated transformers.

The copper remains sufficiently cool due to the exposed large winding areas. A high current density in the wires can, therefore, be allowed which saves copper.

The no-load losses in a toroidal are very small, about 1.1W/kg (0.5W/lb). As the no-load losses of a transformer add to the total heat generation, further material savings are therefore possible.

All of the above reasons contribute to the light weight of the toroidal transformer which is normally less than half the weight of a conventional transformer.
On this web site we will give you a brief technical presentation and information of certain standard data like physical size, weight, loss, data, etc.
You can use this data as guide lines to determine what size of transformer your application requires. But please contact us for our recommendations of what
design will best suit your needs.

General specification input line voltage:

120 or 240V

Frequency: 50/60Hz

Operating range: 47 to 400Hz

Secondary voltage tolerance within 5% at nominal input and full load

Flash tested: 4 KV peak

Leads: 200mm long P.V.C. insulated

The transformers are designed for an ambient temprature at 40degC max

Manufactured according to:
UL & CSA are available upon request.

Harbuch Transformers meet modern day requirements for a smaller size, low magnetic interference field transformer.  The main isolation consists of a triple layer of 50 micron class b (130degC) melinex tape which maintains a dielectric to greater than 4KV.

The secondary windings provide insulation up to 500V AC. The output voltage tolerance is +/- 5%, conforming to BS3535 and CEE15. All voltages are quoted at FULL LOAD. Add the appropriate regulation figure to obtain the off load voltage . At full VA rating the maximum temprature rise is less than 65 degrees above ambient, allowing a maxium ambient of 40 degrees. This allows the transformer to operate up to 105 degrees (class A), which is the maximum for PVC sleeving.

Standard primaries are single 240V 50Hz. Standard secondaries are two identical windings which may be connected in series or parallel, thus doubling the output voltage or current respectively.

Standard termination consists of 200mm of PVC sleeved winding wire with 10mm stripped bare copper.

For mains fusing it is recommended that a delay or anti-surge fuse be used, especially for transformers with ratings in excess of 300VA. The mounting kit supplied allows easy mounting to a chassis by placing a neoprene washer below and above the transformer and bolting the dished washer down firmly on the top.

To minimise the risk of damage to the windings, the bolt should not be over-tightened and both ends of the bolt must not be allowed to simultaneously come into contact with the metal chassis as this would act as a shorted turn.

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