A custom transformer quote is only as accurate as the data behind it. This is the list we work from. You do not need every field to start a conversation, but each one you can fill removes a clarification round and usually a week from the schedule.
Electrical ratings
- Rated power, in kVA or MVA
- Primary voltage and secondary voltage, with tolerances
- Frequency: 50 Hz, 60 Hz, or a non-standard value
- Phase: single or three phase
- Rated current, particularly on the secondary for high current designs
- Vector group, or leave it to us if you have no preference
- Short circuit impedance, as a percentage, or as a range
Regulation and tapping
- Tap range, as a percentage above and below nominal
- Number of tap steps
- Off-circuit or on-load tap changing
- Whether regulation is manual, motorised, or automatic
The duty cycle
This is the field most often left blank, and it is the one that changes the design most. Is the load continuous at full output, intermittent, or cyclic with defined overload periods? A furnace, a rectifier, and a building distribution transformer of identical kVA are three very different machines.
- Load profile over a representative period
- Overload magnitude and duration, and how often it occurs
- Expected daily operating hours
- Whether the load is linear or generates harmonics
Site and environment
- Ambient temperature range, and whether the unit is indoor or outdoor
- Altitude, which affects both cooling and insulation clearances
- Humidity, salt spray, dust, or corrosive atmosphere
- Installation space and any restriction on dimensions or weight
- Access constraints: door widths, lift capacity, whether cranage is available
- Noise limits, especially near occupied areas
Construction preferences
- Dry type, cast resin, or oil immersed
- Winding material: copper or aluminium
- Insulation class: F or H
- Enclosure and IP rating
- Cooling method (AN, AF, OFAF, or OFWF), and which medium is actually available on site
- Terminal arrangement and cable entry direction
Standards, testing, and documentation
- Applicable standard: IEC 60076, GB 1094, ANSI, or a customer specification
- Whether type tests are required or routine tests are sufficient
- Whether third party inspection or witness testing is required
- Documentation format and language
- Spare parts, if any
Commercial
- Quantity, including any future repeat volume
- Required delivery date and destination port
- Whether an OEM built-to-print arrangement or an ODM engineered design applies
- Branding, nameplate, and packing requirements for OEM orders
If you only have a datasheet
Send it. The enquiry form accepts a specification upload, and a drawing or an old nameplate photograph is often enough to reconstruct the rest. We will come back with what we can determine and a short list of what still needs confirming.
A note on what we will and will not do
If a requirement falls outside what we have built before, we will say so at the enquiry stage rather than quote and discover it later. We would rather lose an order than deliver a unit that does not do the job.
See the custom transformer range, or contact us with whatever you have.
Where this fits in a wider installation
Transformers rarely sit on their own. In most projects this equipment ends up inside a package that also carries the medium-voltage switching and the low-voltage distribution. That arrangement is described on our compact substations, transformer substation packages, industrial power distribution and custom transformers pages.
Frequently Asked Questions
What matters most with the information a custom design needs?
It is the specification, not the equipment. Most of what goes wrong later traces back to a voltage, fault level or site condition that was assumed rather than confirmed. The questions below cover what comes up most often.
What makes a transformer custom rather than standard?
Any requirement that falls outside the standard product range. An unusual voltage ratio, a rating between standard steps, a non-standard impedance, a specific vector group, a mechanical envelope constrained by an existing room, or a combination of several of these.
How long does a custom design take?
It follows the drawing approval, not the other way round. The design is settled from your specification and issued for review; production starts once that drawing is approved. Projects that need to move quickly are usually the ones where the specification is complete at the start.
Which standard applies, and is it certified?
The applicable standard and clause set are agreed against your project specification before production starts. Where a project names IEC 60076 for the transformer, we work to those clauses and the routine test report ships with the unit.
What do you need from us to quote?
The single-line diagram or a description of the application, the voltages, the load with its duty, the site conditions, and any standard the project specifies. Send what you have – if something is missing, it can be worked out together rather than delaying the enquiry.