Toroidal Power Transformer TT Series, 20 VA to 1500 VA, 50/60 Hz, 220 V Primary, Custom Secondary, Low Noise

1. Product Name

TT is the series name, not a single model. This series covers a toroidal power transformer wound with copper wire on a grain-oriented silicon steel ring core, with a power range of 20 VA to 1500 VA, operating frequency 50 Hz or 60 Hz, primary 220 V, led out with two red leads, and secondary with two blue leads. As the secondary winding is custom-wound to order, the VA rating is the only parameter that remains constant throughout the series; the corresponding voltage and current vary with each manufacturing run.

The model designation follows the pattern: TT, VA rating, primary voltage, secondary voltage. TT1000-220-24 indicates a 1000 VA specification with primary 220 V and secondary 24 V; TT50-220-24 indicates the same construction for a 50 VA specification. Please treat this as a general pattern for model identification rather than a published coding rule, and provide the full model when ordering.

2. Core and Construction

The core is formed by winding grain-oriented silicon steel strip into a ring and bonding it, creating a closed circular magnetic path with no air gap, and the grain direction aligns with the flux path. This achieves three advantages impossible with laminated cores: eliminating the air gap required when cutting the core; confining the magnetic field within the ring so minimal flux leaks to the surroundings; and eliminating the loose lamination stack that would hum at twice the mains frequency. The supplier panel indicates grain-oriented silicon steel and pure copper wire but does not specify the exact grades of either.

The winding is distributed evenly around the entire ring rather than concentrated on one side, which allows the copper wire to cover the full circumference and shorten the average turn length. Each winding is led out as a pair of insulated leads with protective sleeves at the exit point. The finished toroidal transformer is first wrapped with white tape, then wrapped in transparent film, and finally secured to the base plate with a bolt. The copper wire can be seen through the film between the outer wrapping and the core, as shown in the close-up view.

3. Windings and Leads

The primary is led out with two leads, and the secondary with two leads. On the 150 VA unit, the label reads “Input 0 V - 220 V” for the red lead pair and “Output 0 V - 60 V” for the blue lead pair, both applicable for 50 Hz or 60 Hz; the 300 VA unit has the same layout with an output of 0 V - 66 V. Throughout the series, red indicates the primary and blue the secondary. Leads exit with protective sleeves rather than terminated ends, so the product leaves the factory without any connectors, terminals, or ferrule terminals.

4. Mounting Method

The toroidal transformer is mounted on a black painted steel base plate larger than the coil, with mounting holes at four corners, and secured from top to bottom through a central hole with a bolt, nut, and washer set. This central fixing ensures the core remains compressed and prevents movement; the four corner holes are used to fasten the base plate to the chassis bottom or side panels. Base plate dimensions, hole diameters, bolt threads, and washer set heights are not specified in the material.

5. Electrical Parameter Range

The table serves as the basis for product selection. Each row corresponds to one rating and is also the only place where the windings are described. Each row specifies a dielectric withstand test of 2500 V DC applied from primary to secondary, with insulation resistance nominally not less than 500 megohms; therefore, these two columns need only be noted once rather than repeated fifteen times. No-load core loss is the only published loss parameter: efficiency, voltage regulation, temperature rise, and leakage inductance are not listed.

5.1 Published Ratings

5.2 Two Clearly Labeled Units

The nameplates in the photos of two units are clearly legible. Both connect 220 V to the red lead pair; the secondary voltages are 60 V and 66 V, respectively, neither matching the 24 V series photos or the table row for the same VA rating. The power ratings match, but the windings are inconsistent.

6. Model Range

All products in the series photos are the same series with the same secondary voltage: all eleven clearly readable plates indicate 24 V, ranging from 50 VA/2.1 A to 1500 VA/62.5 A. Each current value is the rated power divided by 24 V, which is the basis for confirming the series rather than relying on any single plate. The smallest unit carries a TT-20 plate but is too small to read at this resolution and is not listed in the table. Each rating in the table corresponds to a different secondary voltage: the two panels represent the same platform with two different winding sets.

6.1 24 V Series

7. Quality and Compliance

The compliance panel displays CE, UL, RoHS, and CCC marks, with a statement below indicating compliance with global safety standards. The 150 VA plate also carries two square marks and a warning triangle. None of these marks are accompanied by certificate numbers, standard references, or test reports, so they are recorded here as marks and statements rather than certified facts. The only expressly specified test is the dielectric withstand test, which is 2500 V DC, not AC.

8. Characteristics

Toroidal core with no air gap.The strip is wound closed, so there is no air gap in the flux path, eliminating the need for excitation current.

Low leakage flux.The magnetic field is confined within the ring, so a toroidal transformer can be placed adjacent to signal-level circuits, whereas a laminated transformer would produce hum interference.

No lamination hum.The wound ring has no loose laminations, so mechanical noise at twice the mains frequency is absent from the start.

Same platform, 20 VA to 1500 VA.The same construction and mounting method apply from the smallest unit to the 1500 W rating.

Secondary wound to order.Voltage, current, taps, and the number of secondary windings are determined by the order, so the same VA value can correspond to multiple voltages.

9. Advantages

Core loss stated explicitly, not implied.Most catalog pages stop at merely listing the VA value. Here, each rating includes its own no-load core loss, which determines the operating temperature of a sealed enclosure.

Insulation clearly specified at both ends.The 2500 V DC withstand test and insulation resistance of 500 megohms or more apply to every row, making the insulation barrier an explicit requirement rather than a recommendation of good practice.

Series product, not a single specification.The fifteen ratings in the table and the eleven units in the series photos cover chassis designs, allowing expansion without changing the mounting method or lead color code.

Mounting hardware pre-installed.The base plate and center bolt are supplied with the product, so the chassis only needs a flat surface and four holes, eliminating the need to design brackets around the transformer.

Fixed core, custom winding.Since only the winding changes between batches, a second voltage requires only changing the winding on a known core, a shorter path than a completely new design.

10. Specifications

Values are transcribed from supplier panels. Where missing, they are marked “not specified”; where the material contradicts itself, the contradiction is pointed out rather than resolved.

10.1 Overview

10.2 Mechanical Parameters

11. Applications

The following uses are categories listed by the supplier for this series, accompanied by a brief explanation of why a toroidal transformer suits each use. They describe the fields in which the series is marketed, not certification of any specific product.

Audio amplifiers.The photo on this page shows a toroidal transformer inside an amplifier next to storage capacitors, a classic application: low leakage flux prevents hum from entering the signal path.

Medical power supplies.Isolated power supplies require documented high-voltage test results, and housings are often sealed, so core loss matters more than efficiency.

Industrial power supplies.Control and drive power supplies require compact isolated supply rails and a mounting plate rather than mounting brackets.

Renewable energy and inverter stages.Auxiliary power and gate drive power supplies inside inverter and converter cabinets.

Instrumentation and test equipment.Bench and rack-mount power supplies where the transformer is placed close to low-level circuits.

12. Ordering

Please provide winding parameters, not just the VA value. A valid inquiry should include the rated power, primary voltage, secondary voltage or list of secondary windings, frequency, desired lead length, whether the base plate and center bolt are required, and quantities per order and per delivery. With this information, the core, wire, turns, and base plate can be determined, and pricing follows. If a chassis already exists, provide the envelope dimensions and mounting hole layout that must be accommodated so that the base plate can be verified before winding begins.

Regarding compliance: the nameplate shows CE, UL, RoHS, and CCC marks and declares compliance with global safety standards. No certificate numbers, standard references, or test reports appear on the nameplate, so these are marks and statements rather than certified facts. The only expressly specified test is a 2500 V DC high-voltage test, with insulation resistance of 500 megohms or more. If your equipment must comply with a particular standard, request certificates and test reports before selecting the design.

Brand/Manufacturer: ZXY, Shenzhen Zhi Xiang Yuan Electronics Co., Ltd. http://www.zxycoil.com