Requesting a transformer core quotation may appear straightforward, but a reliable price cannot be calculated from transformer capacity alone.
Two transformer cores with the same rated power may have completely different dimensions, CRGO grades, core weights, joint structures, manufacturing tolerances and assembly requirements. These differences directly affect material consumption, production time, packing method and final cost.
For transformer manufacturers, submitting complete technical information at the quotation stage helps avoid inaccurate pricing, specification disputes and production delays.
This guide explains what information a transformer core manufacturer needs before preparing an accurate technical and commercial quotation.
Why Transformer Capacity Is Not Enough for Quotation
A request such as “Please quote a 1,000 kVA transformer core” does not provide enough information for accurate pricing.
Transformer capacity is only one design parameter. The final core depends on several additional factors, including:
- Transformer type
- Voltage class
- Frequency
- Core dimensions
- Magnetic flux density
- CRGO steel grade
- Lamination thickness
- Step-lap structure
- Core weight
- Assembly condition
- Required no-load loss
- Order quantity
- Packing and transportation method
A preliminary estimate may be possible without drawings, but the final quotation should be based on approved technical data.
1. Transformer Type and Application
The buyer should first identify the transformer application.
Common examples include:
- Oil-immersed distribution transformers
- Oil-immersed power transformers
- Dry-type transformers
- Renewable energy transformers
- Rectifier transformers
- Furnace transformers
- Traction transformers
- Special-purpose industrial transformers
The application influences the core structure, insulation arrangement, window dimensions, clamping method and required magnetic performance.
The buyer should also specify whether the core is for a new transformer design, an existing production model or replacement manufacturing.
2. Rated Power, Voltage and Frequency
The basic electrical parameters should include:
- Rated power in kVA or MVA
- High-voltage rating
- Low-voltage rating
- System frequency
- Number of phases
- Vector group, where relevant
- Tap range and tap arrangement
- Applicable technical standard
Frequency is especially important because CRGO loss characteristics and core cross-sectional requirements differ between 50 Hz and 60 Hz designs.
Voltage and capacity information alone cannot replace a complete core drawing, but these parameters help the supplier review whether the proposed dimensions and material selection are technically reasonable.
3. Transformer Core Drawing
A detailed drawing is the most important document for an accurate transformer core quotation.
The drawing should clearly indicate:
- Limb width
- Yoke width
- Window height
- Window width
- Center distance
- Core diameter
- Overall core height
- Overall core width
- Lamination lengths
- Step-lap positions
- Stacking sequence
- Number of laminations per step
- Cooling ducts, where required
- Clamping and support details
Drawings may be supplied in PDF, CAD or another readable engineering format.
Every critical dimension should have a clear unit and tolerance. Unclear dimensions can cause incorrect weight calculations or assembly problems during transformer production.
For repeat orders, the drawing revision number should also be stated. This prevents an outdated drawing from being used for production.
4. CRGO Steel Grade and Thickness
The buyer should specify the required grain-oriented electrical steel grade whenever the transformer design has already been finalized.
Important material information includes:
- CRGO or GOES grade
- Nominal thickness
- Maximum specific core loss
- Minimum magnetic induction
- Coating requirement
- Steel mill preference, if applicable
- Domain-refined or conventional material
- Material certificate requirement
Common lamination thicknesses include 0.20 mm, 0.23 mm, 0.27 mm and 0.30 mm. However, the correct thickness should be selected according to the transformer design, loss target, noise requirement and commercial balance.
A thinner material does not automatically guarantee a better final transformer. Cutting quality, mechanical stress, joint construction and assembly control remain critical.
When the buyer has not selected a specific CRGO grade, the supplier should receive the target no-load loss, excitation current and magnetic flux density so that suitable material options can be evaluated.
5. Magnetic Flux Density and No-Load Loss Target
The transformer core manufacturer should understand the electrical performance expected from the finished transformer.
The buyer should provide:
- Designed magnetic flux density
- Target transformer no-load loss
- Maximum excitation current
- Noise requirement, where applicable
- Design tolerance or performance margin
- Applicable efficiency requirement
The no-load loss of the finished transformer is not determined by the core material alone. It is influenced by the winding design, core geometry, material properties, joint structure, manufacturing stress and final transformer assembly.
For this reason, the supplier should manufacture according to the approved design rather than make unsupported guarantees based only on the nominal CRGO loss value.
6. Step-Lap Joint Structure
The joint design has a major influence on manufacturing complexity and magnetic performance.
The RFQ should identify:
- Butt-lap or step-lap construction
- Number of step positions
- Step length
- Lamination quantity per step
- Joint overlap
- Stacking direction
- Yoke and limb assembly sequence
For a customized multi-step-lap transformer core, the supplier should follow the buyer’s approved drawing and stacking sequence.
Changing the step-lap structure without engineering approval may affect core dimensions, excitation current, no-load loss and audible noise.
Where the buyer does not yet have a finalized step-lap design, the supplier can review the main core dimensions and performance target before production. Final responsibility for transformer electromagnetic design should remain clearly defined between both parties.
7. Required Supply Condition
Transformer cores can be supplied in several conditions. The buyer must specify the required delivery form before quotation.
Loose Laminations
All laminations are cut, classified, packed and delivered for assembly at the buyer’s factory.
This option can reduce shipping volume but requires the buyer to have experienced core stacking personnel and suitable assembly equipment.
Pre-Stacked Core Packages
Laminations are arranged into controlled packages or sections according to the stacking sequence.
This reduces local assembly work while maintaining greater transportation flexibility than a fully assembled core.
Fully Assembled Transformer Core
The core is completely stacked and assembled before shipment.
This reduces assembly work at the transformer factory but requires more careful lifting, reinforcement, packing and transportation control.
SKD or CKD Supply
The core and related transformer components are supplied in semi-knocked-down or completely knocked-down form according to the project scope.
The quotation must clearly define which components, accessories, technical documents and assembly services are included.
8. Quantity and Purchasing Schedule
The required quantity affects material planning, cutting optimization and production scheduling.
The buyer should state:
- Prototype quantity
- Initial trial order quantity
- Expected batch quantity
- Annual purchasing volume
- Required delivery date
- Planned repeat-order frequency
A one-unit prototype and a recurring production order may have different pricing structures.
For repeat production, stable drawings and regular purchasing forecasts can improve material utilization, production efficiency and delivery planning.
9. Inspection and Documentation Requirements
Inspection requirements should be confirmed before the supplier calculates the quotation.
Possible documents include:
- CRGO material certificate
- Material traceability record
- Dimensional inspection report
- Burr measurement record
- Core weight record
- Production photographs
- Assembly photographs
- Packing photographs
- Test report
- Certificate of origin
- Packing list
- Commercial invoice
- Third-party inspection report
Additional testing, special documentation or third-party inspection may increase the project cost and lead time. These requirements should not be added after production has already started.
10. Packing and Transportation Requirements
CRGO electrical steel is sensitive to moisture, impact, deformation and mechanical stress.
The buyer should confirm:
- Destination country
- Destination port
- Sea, air, rail or road transportation
- Container or less-than-container shipment
- Maximum package dimensions
- Maximum package weight
- Forklift or crane handling conditions
- Wooden case, steel frame or pallet requirement
- Moisture protection requirement
- Long-term storage conditions
Large assembled transformer cores require special attention because incorrect lifting or transportation may deform the core and introduce mechanical stress into the laminations.
The supplier should design the packing method according to the core size, supply condition, transportation route and unloading method.
11. Information Required for a Fast Preliminary Quotation
When a complete engineering drawing is not yet available, the buyer can provide the following minimum information:
- Transformer type
- Rated capacity
- Voltage ratio
- Frequency
- Number of phases
- Main core dimensions
- Estimated core weight
- Required CRGO grade
- Designed flux density
- Target no-load loss
- Step-lap requirement
- Supply condition
- Order quantity
- Destination port
- Required delivery date
This information may support a preliminary price estimate. A final quotation should still be confirmed after the supplier reviews the complete drawing and technical specification.
Common RFQ Mistakes That Cause Incorrect Quotations
Requesting a Price Based Only on kVA
The same transformer capacity can use different core dimensions, steel grades and magnetic designs.
Sending an Unclear Drawing
Missing dimensions, unreadable notes or conflicting revision numbers create pricing and production risks.
Not Specifying the Material Grade
Different CRGO grades can create a significant difference in raw material cost and transformer performance.
Ignoring the Supply Condition
Loose laminations and fully assembled cores require different labor, packing and transportation arrangements.
Providing Only Net Core Weight
The quotation may also need to consider processing loss, manufacturing yield, packing weight and auxiliary materials.
Adding Inspection Requirements After Order Confirmation
Late changes may increase both production cost and delivery time.
How Chenfan Electric Supports Custom Transformer Core Projects
Chenfan Electric manufactures customized CRGO transformer cores for oil-immersed and dry-type transformer manufacturers.
Our production scope includes:
- CRGO coil slitting
- Precision lamination cutting
- Multi-step-lap processing
- Core stacking
- Fully assembled cores
- Pre-stacked and loose-lamination supply
- Dimensional inspection
- Export packing
Key manufacturing controls include burr height below 0.02 mm, accurate step-lap alignment and a stacking factor above 97% under suitable material and core structure.
With approximately 3,000 tons of CRGO inventory, daily processing capacity of around 50 tons and monthly production capacity of approximately 1,500 tons, we can support both trial orders and recurring transformer manufacturing programs.
Our maximum processing width is 890 mm. Standard projects can be arranged with a short production cycle, while the final lead time depends on the core size, quantity, material grade, assembly condition and inspection requirements.
Frequently Asked Questions
Can a transformer core be quoted without a drawing?
A preliminary estimate may be prepared from the main dimensions, estimated weight, CRGO grade and technical parameters. A final production quotation normally requires a complete drawing.
Can the supplier recommend a CRGO grade?
Yes. The supplier can evaluate available material options when the buyer provides the designed flux density, target no-load loss, frequency and transformer application.
Should the quotation be based on theoretical or actual weight?
The commercial basis should be agreed before order confirmation. Depending on the project, pricing may be based on drawing weight, calculated weight, finished net weight or actual shipment weight.
Can fully assembled transformer cores be exported?
Yes. Fully assembled cores can be exported, but the packing, reinforcement, lifting and transportation method must be designed according to the core dimensions and weight.
What affects the transformer core delivery time?
The main factors include CRGO availability, drawing complexity, order quantity, lamination width, step-lap design, assembly condition, inspection requirements and packing method.
Conclusion
An accurate transformer core quotation requires more than transformer capacity and estimated weight.
The most reliable RFQ includes a complete core drawing, CRGO specification, magnetic design parameters, step-lap details, supply condition, inspection requirements, order quantity and destination information.
Providing these details at the beginning allows the transformer core manufacturer to calculate material consumption correctly, confirm manufacturing feasibility, plan production and prepare suitable export packing.
For customized transformer core projects, send the technical drawing together with the required material grade, quantity, supply condition and target delivery date. Chenfan Electric will review the manufacturing details and prepare a project-specific quotation.