Custom Transformer, Inductor & Magnetic Components FAQ
KATOY develops custom transformers, inductors, chokes, reactors and other magnetic components for industrial electronics and OEM equipment. This FAQ answers common engineering and project questions about magnetic design, operating conditions, customization, samples, testing and compliance.
For a custom project, the most useful starting information is the electrical function of the component together with available voltage, current, power, frequency, waveform, inductance, insulation, thermal, dimensional and mounting requirements. A drawing, existing sample or equipment specification can also be used as a reference.
Engineering & Product Design
What is the difference between a toroidal transformer and an EI laminated transformer?
A toroidal transformer uses a ring-shaped magnetic core, while an EI laminated transformer uses stacked E- and I-shaped laminations. Toroidal construction can provide a compact magnetic path and may reduce stray magnetic field in some designs, while EI construction is often flexible for mounting, multiple windings and cost-sensitive industrial applications.
Actual efficiency, temperature rise, voltage regulation, acoustic noise and size depend on core material, flux density, VA rating, winding design, mounting and operating conditions. Neither construction is universally better; the correct choice depends on the equipment requirements.
What is the difference between a low-frequency transformer and a high-frequency transformer?
The main difference is operating frequency, which affects core material, turns count, winding construction, losses, insulation, size and thermal behavior. A 50/60 Hz transformer commonly uses a laminated electrical-steel core, while a high-frequency transformer in a switching converter commonly uses ferrite or another material selected for the switching frequency and topology.
Higher operating frequency can reduce the size required for magnetic energy transfer, but it also makes core loss, AC winding loss, leakage inductance and parasitic capacitance more important. Higher frequency does not automatically mean higher efficiency.
What causes excessive temperature rise in a transformer?
Transformer temperature rise is mainly determined by total losses and the ability of the construction to dissipate heat. Important contributors include copper loss, core loss, current density, waveform, frequency, loading, ambient temperature, ventilation, winding arrangement and mechanical enclosure.
Reducing one loss mechanism can increase another. For example, adding turns may reduce flux density and magnetizing current, but it can also increase copper length and winding resistance. Thermal design therefore requires a balance between core, copper, insulation, available space and real operating conditions.
Does a higher switching frequency always improve transformer efficiency?
No. Increasing switching frequency can reduce the magnetic size required for a given converter design, but it can also increase core loss, skin and proximity effects in the windings, leakage-related loss and switching-related stress.
The optimum frequency depends on converter topology, core material, flux density, winding structure, power level, cooling and efficiency target. Frequency should therefore be selected as part of the complete power-conversion design rather than optimized in isolation.
How is a 50/60 Hz EI transformer design balanced between turns, flux density and copper loss?
For a given core area and applied voltage, increasing the number of primary turns reduces flux density and generally lowers magnetizing current. However, more turns also increase copper length, winding resistance and the space required in the bobbin window.
A practical EI transformer design balances core loss, copper loss, temperature rise, voltage regulation, insulation and available winding space. The correct operating point depends on core material, VA rating, ambient conditions and the equipment’s duty requirements.
What is the difference between a common-mode choke and a differential-mode inductor?
A common-mode choke is primarily designed to present high impedance to noise that appears in the same direction on multiple conductors, while allowing the intended differential current to pass with relatively little impedance. A differential-mode inductor is primarily used to impede current or noise that flows between the conductors.
The two functions require different magnetic and winding considerations. Core material, coupling, leakage inductance, saturation, current, frequency and EMI target must be considered according to the actual circuit.
What should be considered when selecting a power inductor besides inductance?
Nominal inductance alone is not enough to specify a power inductor. The design should also consider RMS and peak current, saturation behavior, DC resistance, AC winding loss, core loss, operating frequency, ripple current, temperature rise, dimensions, insulation and mounting.
Inductance may also change with current, temperature and core operating point. For converter applications, the component should be evaluated under the actual ripple waveform and thermal conditions rather than only at a small-signal test point.
What is the difference between rated current and saturation current in an inductor?
Rated current and saturation current describe different limits. Rated current is typically associated with an allowed temperature rise or current-carrying capability, while saturation current describes the point at which the magnetic core loses a defined amount of effective inductance because the core is being driven toward saturation.
The exact definitions depend on the manufacturer and test method. Both thermal and magnetic limits must be checked when selecting an inductor for a real circuit.
What is the difference between a power inductor and an electrical reactor?
The terminology overlaps because both are inductive magnetic components. In power electronics, “power inductor” commonly refers to components used for energy storage, ripple filtering or converter functions, while “reactor” is often used for larger industrial inductive components used for current limiting, filtering or waveform conditioning.
The name alone does not define the design. Current, inductance, frequency, core material, saturation, winding resistance, insulation, temperature and the component’s function in the circuit are more important than the label.
What causes leakage inductance in a high-frequency transformer?
Leakage inductance is produced by magnetic flux that links only part of the winding system rather than coupling all relevant windings. It is strongly influenced by winding geometry, spacing, insulation thickness, winding order, interleaving and the physical relationship between primary and secondary windings.
Lower leakage inductance can be beneficial in many switching converters, but aggressively reducing spacing or interleaving windings can affect insulation, capacitance and manufacturability. Leakage inductance therefore has to be controlled together with safety, parasitic capacitance and winding loss.
Customization & Project Inputs
What information does KATOY need to evaluate a custom transformer or magnetic component?
The most useful information depends on the component, but typical inputs include input and output voltage, current or power, operating frequency, waveform, topology, inductance where applicable, insulation requirements, ambient and operating temperature, dimensions, mounting method and the function of the component in the circuit.
For high-frequency transformers, switching topology and switching frequency are particularly important. Existing drawings, schematics, specifications, photographs or reference samples can also help KATOY evaluate the project. For project submission, use the contact page.
Can KATOY manufacture from an existing drawing, specification or sample?
Yes. KATOY can evaluate customer-provided electrical drawings, mechanical drawings, specifications and reference samples. The engineering team reviews the available information for manufacturability and identifies missing electrical, thermal, insulation or mechanical requirements before sample development.
A reference sample can be useful when documentation is incomplete, but critical electrical and safety requirements should still be confirmed before production.
Can KATOY develop a sample before recurring production?
Yes. Sample development can be used to verify electrical performance, dimensions, mounting, insulation and other project-specific requirements before recurring production.
Prototype timing depends on design complexity, material availability, tooling, validation requirements and revision cycles. The expected schedule is confirmed after the engineering requirements are reviewed.
Do I need a complete specification before contacting KATOY?
No. A project can begin with the information currently available, such as a drawing, existing sample, equipment model, input/output requirement or basic electrical parameters.
KATOY can help identify additional information needed for engineering evaluation. However, final design approval and production require the critical electrical, thermal, mechanical and safety requirements to be confirmed.
Quality, Testing & Compliance
What quality and compliance support is available for KATOY magnetic components?
KATOY operates an ISO 9001:2015 quality management system covering product development, manufacturing and quality control. RoHS- and REACH-compliant materials can be used according to project requirements, and UL-recognized materials can be selected where required.
CE conformity support and CQC-certified products are available for applicable projects. Certification and compliance requirements should be confirmed for the specific product and end application rather than assumed to apply universally to every KATOY product.
What electrical tests can be used for custom transformers and inductors?
The required inspection and test plan depends on the product and project. Applicable checks may include winding resistance, turns ratio, inductance, no-load current, insulation resistance, dielectric withstand, polarity, dimensions and other agreed electrical parameters.
Additional validation such as load, temperature-rise or application-specific testing can be defined when required by the project. The exact checks performed are confirmed in the agreed control plan, because not every test applies to every product.
Can KATOY provide test records or project-specific reports?
Test records and project-specific reports can be provided according to the agreed product requirements and inspection plan. The report content may include relevant electrical parameters, dielectric or insulation test results, dimensional checks or other project-specific validation data.
If a customer requires a particular report format, traceability item or test method, it should be defined during the project review.
How should insulation requirements be specified for a custom transformer?
Insulation requirements should be based on working voltage, dielectric withstand requirement, insulation system, creepage and clearance needs, operating temperature, pollution environment, end-equipment standard and any reinforced or basic insulation requirement.
Thermal class alone does not fully define electrical insulation performance. Material selection and physical construction must be evaluated together with the applicable safety requirements.
Samples, Production & Commercial Process
What is the MOQ for a custom transformer or inductor project?
MOQ depends on the product type, material requirements, tooling, manufacturing process and project stage. Prototype and small validation quantities can be discussed before recurring production.
For an accurate MOQ, KATOY should review the product requirements rather than publish one fixed quantity for all custom magnetic components.
How is production lead time determined?
Production lead time depends on product complexity, material availability, tooling, approved sample status, order quantity and required inspection or validation.
The production schedule is confirmed with the quotation or order after the design and supply requirements are clear.
What commercial terms apply to a custom project?
Commercial terms are confirmed in the quotation or order agreement and may vary according to the product, project stage, order value and cooperation history.
Commercial terms are therefore agreed for the specific project rather than published as one universal payment structure.
Have a Custom Magnetic Component Project?
Send KATOY the available electrical requirements, drawing, specification or reference sample. You do not need every parameter at the first contact; our team can help identify the additional information required for project evaluation.