Custom transformer orders fail for boring reasons. Not usually because the design was wrong, but because one parameter was never confirmed - a vector group assumed rather than stated, a frequency taken from an old project, an installation altitude nobody asked about. Most of the checks below take minutes to confirm and save weeks later.
Electrical Parameters
Capacity in kVA, primary and secondary voltage, frequency (50 or 60 Hz), number of phases, and vector group. Vector group deserves separate attention: Dyn11 is common, but if the unit will parallel with existing equipment, the group must match exactly, and this is the single most common omission in custom enquiries. Impedance should also be stated if the utility specifies it - a 500 kVA Distribution Transformer ordered with default impedance may not coordinate with upstream protection the way the utility expects. Tapping range and tap changer type (off-circuit or on-load) follow from how much voltage variation the line actually sees.
Cooling, Environment & Enclosure
Cooling type (ONAN, ONAF, ANAF) affects both capacity and physical size, and it should be chosen against the actual load profile, not copied from a previous order. Installation environment is where custom orders most often go wrong: indoor or outdoor, ambient temperature range, altitude above 1,000 m, humidity, and pollution level all change insulation and creepage requirements. If the unit goes into a coastal or heavily polluted site, say so at enquiry stage - creepage distance and coating decisions are made during design, not after delivery.
Standards, Testing & Delivery
State the applicable standard (IEC 60076, ANSI, or a local utility specification) and whether the utility has its own loss limits - a unit can meet IEC 60076 and still fail a local efficiency threshold. Agree on which test reports will be supplied and whether third-party inspection is required before dispatch. On delivery, confirm the required documentation (test report, drawings, packing list), the shipping terms, and whether the site can handle the unit's weight and dimensions on arrival. These are commercial details, but they cause as many delays as technical ones.
About Hebei Hozee Electric Co., Ltd.
Hebei Hozee Electric Co., Ltd. manufactures oil-immersed transformers, dry-type transformers, single-phase transformers, and transformer cores including laminated cores and single-phase wound cores. For custom orders, our engineering team reviews the parameter list within 24–48 hours and flags anything that looks inconsistent before drawings are issued - a frequency that does not match the stated country, a vector group that will not parallel, an altitude that requires derating. If you are preparing a Power Transformer enquiry and want the parameter list checked before quotation, send it to us and we will confirm the points that need clarification.