What determines the accuracy of high-frequency transformer windings in high-voltage power supplies? Let's delve into the manufacturing process.
1. Core Design Decisions Before Winding: Laying the Foundation for High-Voltage Performance
As the "voltage conversion core" of a High voltage power supply, the winding process of high-frequency transformers must first address three key contradictions in high-voltage scenarios: balancing turns requirement with volume control, reconciling insulation strength with parasitic parameters, and matching high-frequency loss with heat dissipation efficiency. Within IDEALPLUSING's production system, three critical design steps are completed prior to winding:
1.1 Customization of Magnetic Core and Winding Scheme
For high-voltage output scenarios of 3600V and above, PQ-type ferrite cores are preferred (offering 40% lower magnetic leakage than EE-type cores due to superior shielding). An air gap calculation tool is used to precisely reserve a 0.1-0.3mm air gap, preventing magnetic saturation under high current. The winding design adopts a "primary split winding + secondary sandwich" structure: the 120 turns of the primary winding are evenly divided into two groups, while the 110 turns of the secondary winding are wound with triple-insulated wire in the middle. This design controls leakage inductance within 5μH — a 60% reduction compared to traditional single-layer winding, directly minimizing voltage spikes across switching tubes.
1.2 Three-Level Protection for Insulation System
Strictly adhering to IEC/EN 61558 safety standards, a triple-insulation setup ("polyimide tape + air gap + epoxy") is implemented between the primary and secondary windings: the first layer consists of 3 wraps of Kapton tape (withstand temperature 260℃, dielectric strength 40kV/mm), a 2mm air gap is reserved in the middle, and an epoxy insulation plate covers the outer layer. This configuration ensures a creepage distance of 12mm, far exceeding the 5mm requirement for 500V-class power supplies. Lead wires are all sleeved with yellow wax tubes and maintained at a minimum 3mm electrical clearance from the magnetic core, completely eliminating the risk of surface leakage.
2. Full Winding Process: Millimeter-Level Precision Control
IDEALPLUSING utilizes numerical control winding machines combined with a tension closed-loop system, controlling winding error within ±1 turn. The core process comprises four key stages:
2.1 Bobbin Preprocessing and Tension Calibration
High-temperature-resistant PBT bobbins (withstand temperature 150℃) are selected. Five layers of barrier tape are first wound on both ends to form an insulation barrier, with a height 2mm higher than the winding — ensuring no direct contact with the magnetic core after assembly. Before winding, the tensioner is calibrated to set the pulling force between 0.8-1.2N: excessive force causes damage to the triple-insulated wire's outer layer (prone to breakdown during withstand voltage testing), while insufficient force results in loose windings and a 30% drop in thermal conductivity.
2.2 Critical Process for Shielding Layer
A copper foil shielding layer is wound around the first group of the primary winding, with a width 2mm narrower than the winding (to avoid short circuits at both ends). The start and end of the foil are isolated with insulation tape, leaving only one end grounded — this reduces common-mode noise by 20dB, enabling the HV power supply to easily pass EN 55022 Class B EMI testing. The shielding layer must be wound without wrinkles; otherwise, parasitic capacitance forms, which degrades high-frequency performance.
2.3 Secondary Winding and Interlayer Insulation
The secondary winding uses 0.1mm-diameter triple-insulated wire. A layer of polyimide tape is applied after every 20 turns, with a 50% tape overlap rate (to avoid insulation weak points). The winding speed is set to 100r/min — 50% slower than the primary winding — preventing wire arrangement chaos caused by centrifugal force on the thin wire. Disordered windings easily lead to local electric field concentration under high voltage, which may trigger insulation breakdown.
2.4 Vacuum Varnish Impregnation and Curing
Immediately after winding, the transformer enters the vacuum varnish impregnation process: first, it is preheated in a 100℃ oven for 2 hours to remove moisture, then placed in a vacuum tank pumped to -0.095MPa. Epoxy resin varnish (breakdown voltage 60kV/mm) is injected, and pressure is maintained for 30 minutes to ensure the varnish penetrates the gaps between each turn. Curing follows a stepped temperature-rise pattern: 60℃/2h → 80℃/4h → 100℃/2h, avoiding coil deformation due to sudden heating. After this process, the transformer's thermal conductivity increases from 0.2W/(m·K) to 0.8W/(m·K), reducing the temperature by 15℃ during full-load operation.
3. Factory Testing: Extreme Verification for High-Voltage Scenarios
Each transformer must pass three core tests before proceeding to the next process:
• Turn Ratio and Inductance Test: A turn ratio tester verifies the 1:9.2 transformation ratio accuracy (error ≤0.5%), while an LCR meter measures the magnetizing inductance at 100kHz, ensuring the deviation is within ±3%.
• Withstand Voltage Breakdown Test: A 5kV AC voltage is applied between the primary and secondary windings for 1 minute, with leakage current required to be <1mA (IDEALPLUSING's internal standard is stricter than the industry's 5mA limit).
• Temperature Cycle Test: 10 cycles of -40℃ to 85℃ are conducted, with 2 hours of heat preservation per cycle. After testing, the change in leakage inductance must not exceed 5% of the initial value.
4. Process Value: Ensuring High-Voltage Reliability Through Details
Although the winding process of high-frequency transformers seems minor, it directly determines the core performance of a High voltage power supply. Through the full-process control of "design protection - precision winding - extreme testing", IDEALPLUSING enables its high-voltage DC power supplies to achieve 100,000 hours of trouble-free operation in harsh scenarios such as medical CT machines and semiconductor etching equipment — behind this lies the support of millimeter-level process precision.
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