INTRODUCING O-CORES

    The performance of a toroidal transformer may be further optimized with an O-Core.

    O-Cores are wound from a grain oriented silicon steel strip, which is continuously pointed towards each end to produce a circular cross section. O-Cores are available in power ratings up to 2000 VA for 60 Hz operation or up to 1600VA for 50/60Hz operation.

    The circumference of a circle is about 12% less than that of a square with same area and 18% less than a rectangle with the same area and a height to width ratio of 2:1 as in the most popular conventional toroidal transformer.


    Since O-Cores have no sharp edges they require less insulation and can be wound with less fill factor resulting in a lighter and smaller transformer than the conventional toroid. Due to a slower production process and a higher scrap factor the O-Cores are more expensive than conventional toroidal transformers so the above benefits of the O-Core transformers come with a premium.
 
Physical size and weight of different power ratings of O-Core transformers.

Power
( VA@60Hz 1) 		Dimensions (Appr.) 2) . inch O.D.xHt. mm. O.D.xHt. Weight (Appr.) Lbs Kg
45 3.0x.1.0 76x24 1.2 0.5
65 3.2x1.0 80x26 1.4 0.6
90 3.4x1.1 86x28 1.7 0.8
115 3.7x1.2 93x30 2.2 1.0
175 3.9x1.3 99x32 2.7 1.2
220 4.2x1.4 105x34 3.2 1.5
275 4.5x1.4 113x36 3.8 1.7
320 4.6x1.5 116x38 4.2 1.9
425 4.9x1.6 124x41 5.2 2.4
550 5.2x1.7 131x43 6.1 2.8
650 5.4x1.8 138x45 6.8 3.1
800 5.7x1.9 144x49 8.5 3.9
1000 6.0x2.05 152x52 9.8 4.5
1300 6.3x2.1 159x54 12.5 5.7
1600 6.7x2.3 169x57 15.0 6.8
2000 7.0x2.4 179x61 17.5 7.9

The O-Core transformers have a diameter to height ratio around 3:1. So when your design only has room for a narrow footprint, a traditional toroidal core is the only choice. Please see page 11 in this brochure regarding the flexible dimensions of our conventional toroidal core designs.

The O-Core is the preferred choice for a low profile and for applications where a low weight is a design priority. Please refer to the chart on this page for examples of physical sizes of O-Core transformers of various power ratings up to 2000VA.

   
 
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