Toroidal Power Transformers

  • Bicron Toroidal Power Transformer Bicron Toroidal Power Transformer
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Toroidal power transformers are popular for their low radiated magnetic field and comparable size & weight to VA rating.  Advantages of a Toroidal Power Transformer over other types of transformer platforms are many.  This is especially true of Toroidal Power Transformers compared to typical laminated transformers. The advantages flow to the bottom line; improved performance and lower cost.  Learn more by viewing our webpage Advantages of Toroidal Power Transformers.

Bicron’s power range for Toroidal Power Transformers covers 20VA to 10,000VA.  Choose from our selection table below for a Standard Toroidal Power Transformer model or complete and return our Toroidal Power Transformer Design Worksheet to specify the custom transformer model that meets your needs.

Whether you select a standard or custom model we will contact you directly to review all performance requirements needed to complete a quotation. Common factors we will review with you include size, power, rating, mounting, height/diameter ratio, lead configuration, agency approval type, insulation and shielding.   
Visit our Technical Guide for Bicron Toroidal Power Transformers for design and application criteria important to the use of our products.

Please clarify your choices from the following options when selecting a Bicron Toroidal Power Transformer:
  • Bicron Safety agency recognitions include Consumer Electronics UL6500 & IEC60065; General Purpose UL506; Medical UL60601-1.
  • Bicron recognized insulation systems: Class B 130°C; Class F 155°C; Class H 180°C.
  • Input voltage; 120V or 120/240V.
  • Secondary voltage; 120V or 240V, or custom voltage. 
  • Secondary; single or dual output.
  • Frequency; 50/60Hz or 60Hz.
  • Temperature range.
  • Mounting styles; Type 1, Type 2, Type 3 or Type 4 (see below).
  • Quantity required.
  • See Figure 11, below, for a sampling of winding and connection alternatives
  • Technical notes, below.

 click here to view image as pdf


Standard Toroidal Power Transformers – Selection Table 

*Links for Datasheets will appear if available       

Toroidal Power Transformers with power up to 10,000VA are available in configurations modified for size, input/output values, leads, shielding, mounting and other considerations.  Please use our Toroidal Power Transformer Design Worksheet to specify your requirements and request a quote.

Winding and connection alternatives:         click here to view image as pdf


Typically, there are three system configura­tions used in conjunction with linear power supplies. The half wave (HW), the full wave (FW), and the full wave center tap (FWCT). Each configuration will have impact on the VA requirements of the transformer and the circuit components comprising the rec­tification and filtering. Please contact Bicron engineering for specific transformer parameters.
Three single phase transformers may be connected to form a 3-phase bank in the configurations shown. Also shown are the voltages and currents based on ideal con­ditions. The VA rating of each transformer is one third the total system regardless of the selected configuration. The voltage and current ratings of each transformer is, how­ever, configuration dependent.
The same transformation of voltage and current can be obtained with a single winding autotransformer as with the nor­mal two winding transformer. There are two major differences:
  1. In the autotransformer, the secondary winding is common to both the primary and secondary wind­ing.
  2. There is a direct copper con­nection between the primary and sec­ondary circuits.
 Autotransformers have lower leakage reactance, lower losses, smaller excitation currents, and they can be smaller and less expensive than dual winding transformers when the voltage ratio is less than 2:1. And, of course, they provide no isolation.
Thermal class is designated by a letter and defines the lowest temperature rating of the materials which make-up the trans­former:
Class A materials (105°C)
Class B materials (130°C)
Class F materials (155°C)
Class H materials (180°C)
The temperature rise of a transformer can be determined by the resistance method:
t = ((R22R1)/ R1)3(234.52t2) 2 (t22t1)
t = temperature rise over ambient, t2 (°C)
R2 = resistance of winding at end of test
R1= resistance of winding at beginning of test
t2= ambient temperature at end of test (°C)
t1= ambient temperature at beginning of test (°C)

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