Toroidal Transformers

Toroidal transformers are devices that transfer electrical energy from one electric circuit to another, without changing the frequency, by the principles of electromagnetic induction. The energy transfer usually takes place with a change of voltage.  Toroidal transformers typically have copper wire wrapped around a cylindrical core so the magnetic flux, which occurs within the coil, doesn't leak out, the coil efficiency is good, and the magnetic flux has little influence on other components.

Important primary specifications to consider when searching for toroidal transformers include primary configuration, primary frequency, and maximum primary voltage rating.  The primary configurations include single, dual, quad (2+2), 5-lead, and ladder.  The size and cost of a transformer increases when you move down the listing of primary windings. A 5-Lead primary requires more copper than a Quad (2+2) primary. A Ladder is the least economical primary configuration.  Primary frequencies of incoming voltage signal to primaries available for toroidal transformers include 50 Hz, 60 Hz, and 400 Hz.  50 Hz is common for European power.  60 Hz is common in North American power.  400 Hz is most widely used in aerospace applications.  The maximum primary voltage rating is another important parameter to consider.  A transformer should be provided with more than one primary winding if it is to be used for several nominal voltages.

Important secondary specifications to consider when searching for toroidal transformers include maximum secondary voltage rating, maximum secondary current rating, maximum power rating, and output type.  A transformer may provide more than one secondary voltage value.  The Rated Power of the transformer is the sum of the VA (Volts x Amps) for all of the secondary windings.  Output choices include AC or DC.  For Alternating Current waveform output, voltage the values are typically given in RMS values. Consult manufacturer for waveform options.  For direct current secondary voltage output, consult manufacturer for type of rectification.

Mountings available for toroidal transformers include chassis mount, dish or disk mount, enclosure or free standing, h frame, and PCB mount.  Agency considerations for toroidal transformers include CE, CB, CSA, cUL, UL, TUV, and VDE.  CE is set by the international commission on rules for the approval of electrical equipment.  The CB certification scheme was initiated in the 1960s and indicates conformity to safety and electrical standards established by the IEC.  It is widely recognized in many countries, including the United States, the European Union, Japan, and Australia.  The Canadian Standards Association sets the CSA.  The cUL mark is applied to products for the Canadian market. Products with this type of mark have been evaluated to Canadian safety requirements. UL signifies Underwriter's Laboratory certified or registered.  TÜV Rhineland/Berlin-Brandenburg provides International Approvals Services as they relate to product safety. Products certified by TÜV Rhineland for the US market are identified by the TUVus certification mark. TÜV Rhineland of North America is also established as a Certification Organization in Canada. When the TUVus mark is coupled with the cTUV mark, the product is certified compliant for both the US and Canadian markets.  The VDE Mark indicates conformity with the VDE standards, or European or internationally harmonized standards, and confirms compliance with protective requirements of the applicable EC Directive(s). The VDE Mark is a symbol for electrical, mechanical, thermal, toxic, radiological and other hazards.

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Part Numbers for Toroidal Transformers