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Toroidal O-Core Power Transformers
Low-profile O-core toroidal power transformers with higher power density in a compact, efficient package. Custom designs for 60Hz or 50/60Hz operation.
Custom O-Core Toroidal Power Transformers – Lowest Profile Design
O-Core power transformers are the preferred choice when the lowest possible profile is a design priority. O-Core transformers have a diameter-to-height ratio of around 3:1, compared to 2:1 for our regular toroidal transformers.
Since O-Cores have no sharp edges, they require less insulation and can be wound with a lower fill factor. This results in a lighter and smaller transformer than a regular toroidal core transformer of the same power rating.
The grain-oriented silicon steel properties of O-Cores are the same as in our regular toroidal cores, giving O-Core transformers the same electrical benefits (low core losses, minimal EMI, high efficiency, and quiet operation). They can be used in designs for the same applications.
If your design requires the smallest possible footprint (diameter), our regular toroidal core is often the better choice as it offers more flexible dimensions.
O-Cores are wound from a steel strip which is continuously pointed toward each end to produce a circular cross section. The circumference of a circle is about 12% less than that of a square with the same area, and 18% less than a rectangle with the same area and a diameter-to-height ratio of 2:1 (as in a typical regular toroidal core transformer).
Why Choose O-Core Toroidal Power Transformers
O-Core transformers combine the proven electrical advantages of grain-oriented silicon steel toroidal cores with a unique circular cross-section that dramatically reduces height. This makes them ideal for space-constrained designs where every millimeter of height matters.
Key advantages include:
- Lowest possible profile (approximately 3:1 diameter-to-height ratio)
- Lighter and smaller overall package than regular toroidal transformers of equal VA rating
- Reduced insulation requirements due to the absence of sharp edges
- Same high efficiency, low core losses, and low EMI as standard toroidal designs
- Excellent for rackmount, slim enclosures, and compact equipment
Specifications
| Power VA @ 60Hz | Power VA @ 50/60Hz | Dimensions * | Weight * |
|---|---|---|---|
| 45 | 36 | 3.0 x 1.0 in (76 x 24 mm) | 1.2 lbs (0.5 kg) |
| 65 | 52 | 3.2 x 1.0 in (80 x 26 mm) | 1.4 lbs (0.6 kg) |
| 90 | 72 | 3.4 x 1.1 in (86 x 28 mm) | 1.7 lbs (0.8 kg) |
| 115 | 92 | 3.7 x 1.2 in (93 x 30 mm) | 2.2 lbs (1.0 kg) |
| 175 | 140 | 3.9 x 1.3 in (99 x 32 mm) | 2.7 lbs (1.2 kg) |
| 220 | 176 | 4.2 x 1.4 in (105 x 34 mm) | 3.2 lbs (1.5 kg) |
| 275 | 220 | 4.5 x 1.4 in (113 x 36 mm) | 3.8 lbs (1.7 kg) |
| 320 | 256 | 4.6 x 1.5 in (116 x 38 mm) | 4.2 lbs (1.9 kg) |
| 425 | 340 | 4.9 x 1.6 in (124 x 41 mm) | 5.2 lbs (2.4 kg) |
| 550 | 440 | 5.2 x 1.7 in (131 x 43 mm) | 6.1 lbs (2.8 kg) |
| 650 | 520 | 5.4 x 1.8 in (138 x 45 mm) | 6.8 lbs (3.1 kg) |
| 800 | 640 | 5.7 x 1.9 in (144 x 49 mm) | 8.5 lbs (3.9 kg) |
| 1000 | 800 | 6.0 x 2.05 in (152 x 52 mm) | 9.8 lbs (4.5 kg) |
| 1300 | 1040 | 6.3 x 2.1 in (159 x 54 mm) | 12.5 lbs (5.7 kg) |
| 1600 | 1280 | 6.7 x 2.3 in (169 x 57 mm) | 15.0 lbs (6.8 kg) |
| 2000 | 1600 | 7.0 x 2.4 in (179 x 61 mm) | 17.5 lbs (7.9 kg) |
Toroidal Transformer O-Coress shine in applications where minimal height and compact form factor are critical.
Medical Devices & Healthcare Equipment
Compact, low-profile power supplies for medical instrumentation, patient monitoring, diagnostic equipment, and other space-constrained healthcare devices.
Industrial Control Panels & Automation
Low-height transformers for compact industrial control panels, PLC power supplies, motor controls, and automation systems with tight enclosure height limits.
Test, Measurement & Laboratory Instrumentation
Precision low-profile transformers for laboratory analyzers, test equipment, calibration systems, and sensitive measurement instruments.
Professional Audio & Hi-Fi Equipment
Ideal for slim audio amplifiers, preamplifiers, DAC power supplies, and professional rackmount audio gear where low profile and hum-free performance are essential.
Rackmount & Telecom / Data Equipment
Excellent for 1U rackmount power supplies, telecom equipment, servers, and other high-density electronic systems where every millimeter of height matters.
Safety Standard Certifications:
- UL 506, UL 1561, UL 5085
- CSA C22.2 No. 66-1988
- EN61588-1, IEC61558-1
- UL Files: E140446, E178316
- Intertek File: 3051384
- CE Mark and RoHS compliant
Medical Applications: Our TIS Series meet IEC 60601-1 Third Edition and equivalents (AAMI/ANSI/UL 60601-1, CSA C22.2 No. 601.1-M90, EN60601.1). Also designed to applicable sections of UL950, IEC950, UL813, UL1236, and many others.
Let's build yours to spec.
Custom magnetics engineered and manufactured in the USA. Tell us your requirements and our engineers will help.
Frequently Asked Questions
What is a toroidal isolation transformer and what is it used for?
An O-core (also called O-core) toroidal transformer uses a circular cross-section instead of the standard rectangular cross-section found in most toroidal transformers. This unique construction delivers the lowest possible profile while maintaining the same high efficiency, low EMI, and quiet operation as regular toroidal designs.
What are the advantages of O-core transformers over regular toroidal transformers?
O-core transformers have a diameter-to-height ratio of approximately 3:1 (vs 2:1 for regular toroids). Because they have no sharp edges, they require less insulation and can be wound with a lower fill factor, resulting in a lighter and smaller overall transformer for the same power rating.
O-core vs regular toroidal transformer – which should I choose for my design?
Choose an O-core transformer when lowest height/profile is your top priority (for example, 1U rackmount equipment or slim enclosures). Choose a regular toroidal transformer when you need the smallest possible footprint (diameter) or more flexible dimension options.
What applications are O-core low-profile transformers best suited for?
O-core transformers are ideal for professional audio equipment, medical devices, industrial control panels, test & measurement instrumentation, 1U rackmount power supplies, telecom equipment, and any compact or height-constrained electronic systems.
What power ratings and sizes are available for O-core power transformers?
Standard O-core transformers are available from 45VA up to 2,000VA at 60Hz (and up to 1,600VA at 50/60Hz). Full size and weight specifications are listed in the table above. Custom ratings and configurations are available.
Can you build custom O-core transformers for specific applications?
Yes. We specialize in fully custom O-core toroidal power transformers for 60Hz or 50/60Hz operation. Our engineers can work with you on voltage, frequency, shielding, mounting, enclosures, and other requirements to meet your exact design needs.
