zishengelectric
Project Partners
Phone/WhatsApp: 8619131285373
Email: info@zishengtransformer.com
Factory Headquarters: No. 118, Jingyi Street, Economic Development Zone.
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Project Partners
Phone/WhatsApp: 8619131285373
Email: info@zishengtransformer.com
Factory Headquarters: No. 118, Jingyi Street, Economic Development Zone.
A 37.5kVA single-phase pad-mounted transformer connects an underground medium-voltage network to a compatible low-voltage single-phase service. Zisheng Electric coordinates the proposed design around the utility specification and installation interfaces. Capacity alone does not determine the voltage, loss level, protection or enclosure dimensions.
The 37.5kVA rating is apparent power. At a load power factor of 0.8, 37.5kVA corresponds mathematically to 30kW; this is not an allowance for motor starting, harmonic heating or future growth. Compared with 25kVA, the unit has 50% more apparent-power capacity. Check diversified demand and operating conditions before choosing between 25kVA, 37.5kVA and the next size.
Coordinate the level foundation, footprint, anchoring, cable openings, cable bending space, door swing, working clearances and lifting access with approved drawings. A locked compartment still requires utility-approved access control and safe working distances.
A dead-front arrangement uses screened, insulated cable connections. Match connector voltage class, current rating and bushing interface as a system. Radial feed normally terminates one incoming circuit; loop feed provides incoming and outgoing circuit interfaces. Switching and fault-interruption functions depend on the accessories specified.
Select the core, winding conductor, insulation and mechanical support together for the agreed duty. Copper or aluminum may be requested subject to engineering confirmation. Compare guaranteed no-load losses, load losses, impedance and temperature rise rather than judging performance by conductor material alone.
ONAN means Oil Natural Air Natural: natural oil circulation transfers heat to the tank and surrounding air without cooling fans. Confirm this designation with the proposed mineral-oil design. An ester-fluid option requires a separate review of thermal performance, insulation and site requirements.
BIL means Basic Impulse Insulation Level, the specified lightning-impulse withstand level. Coordinate BIL, power-frequency withstand, cable terminations and surge protection with the actual system voltage; a 37.5kVA rating does not establish these values.
Provide site altitude, maximum and minimum ambient temperatures, humidity, salt exposure, flood risk and seismic requirements. Coastal, high-altitude and unusually hot locations require a review of insulation, thermal design, coating and foundation conditions.
State the destination utility specification and applicable standard with its edition in the inquiry. For an ANSI/IEEE design, agree the relevant IEEE C57 requirements for the transformer, enclosure and tests. A standards reference describes a design requirement; product certification and market-specific efficiency compliance require separate evidence for the offered configuration.
For an RFQ, provide the maximum diversified kVA demand, power factor, motor starting duty, harmonic loads, future growth and service voltage. Include the utility one-line diagram, system grounding, required frequency, altitude and ambient conditions.
Confirm primary winding voltage separately from system line-to-line voltage. For a center-tapped secondary, state both end-to-end and line-to-neutral voltages and the expected load balance. Coordinate bushings, connectors, grounding points, cable access, foundation dimensions and external protection with the installation team.
Before releasing manufacture, approve the data sheet, terminal diagram, general arrangement, accessory list and guaranteed performance schedule. The 37.5kVA page is a selection starting point; the accepted technical documents define the supplied unit.
This proposal considers a 37.5kVA single-phase pad-mounted transformer for a residential service group connected to an underground distribution network. The intended loads include household lighting, appliances and compatible single-phase air-conditioning equipment.
The installation requires an enclosed cable termination area, a foundation coordinated with underground conduits, and clear access for authorized utility personnel.
| Parameter | Proposed Specification |
|---|---|
| Rated capacity | 37.5kVA |
| Phase | Single phase |
| Installation | Ground-level pad with underground cable entry |
| Primary voltage | Matched to the utility supply and approved winding connection |
| Secondary service | Selected for the residential service arrangement |
| Frequency | Matched to the supply network |
| Feed arrangement | Radial or loop feed, selected from the network design |
| Protection | Coordinated primary protection, surge protection and grounding |
| Installation dimensions | Defined by the approved general arrangement drawing |
The capacity review should use diversified household demand rather than the sum of connected appliance ratings. Air-conditioning starting current, electric heating, vehicle charging and future expansion require separate consideration.
For a center-tapped secondary, the design should also review the distribution of line-to-neutral loads between the two winding sections. Cable sizing must account for current, installation conditions and voltage drop.
Before civil construction, coordinate the transformer base, cable openings, conduit positions and anchoring arrangement. The layout should provide door-opening clearance, cable bending space, drainage and access for lifting or replacement.
Connector interfaces, grounding points and external protection responsibilities should be agreed between the equipment supplier, utility and installation contractor.
The procurement package should define the approved drawings, nameplate schedule, applicable routine-test records and accessory list. Any witnessed factory acceptance testing requires an agreed scope and acceptance criteria.
For transport, support and secure the transformer through approved structural points. Protect bushings, terminals and projecting fittings from packing members. On arrival, inspect the enclosure, accessories and sealing condition before installation.
| Parameter | Specification |
|---|---|
| Rated capacity | 37.5kVA |
| Number of phases | Single phase |
| Installation | Pad mounted; underground cable entry |
| Primary voltage | To be selected to match the utility system and winding voltage |
| Secondary voltage | To be selected; specify terminal voltage and any center-tapped service |
| Frequency | 50Hz or 60Hz, subject to design confirmation |
| Polarity / connection | To match the approved winding and terminal diagram |
| Cooling | ONAN for the proposed mineral-oil design; confirm with the offered configuration |
| Winding material | Copper or aluminum, subject to engineering confirmation |
| Impedance | To be agreed for the selected voltage and design |
| Insulation level | Power-frequency and lightning-impulse withstand requirements to be agreed |
| Temperature rise | To be agreed under the selected standard and site conditions |
| Losses / efficiency | Guaranteed values and applicable regulatory basis to be confirmed for this configuration |
| Altitude / ambient conditions | Provide altitude, ambient range and special environmental exposure |
| Fluid / tank finish | Specify fluid, tank material and corrosion-protection requirements |
| Dimensions / net weight / oil quantity | Subject to the approved model drawing and data sheet |
| Packing dimensions / gross weight | Subject to the approved shipping arrangement |
| Accessories | Bushings, grounding, fuses, switches and indicators as specified in the order |
Confirm primary winding voltage, secondary arrangement, 50Hz or 60Hz frequency, radial or loop feed, copper or aluminum winding, fluid type, corrosion protection and accessories with the offered design. Specify dead-front connector interfaces, fuse and switch requirements, grounding and utility approval conditions in the RFQ.
For an RFQ, provide the maximum diversified kVA demand, power factor, motor starting duty, harmonic loads, future growth and service voltage. Include the utility one-line diagram, system grounding, required frequency, altitude and ambient conditions.
Confirm primary winding voltage separately from system line-to-line voltage. For a center-tapped secondary, state both end-to-end and line-to-neutral voltages and the expected load balance. Coordinate bushings, connectors, grounding points, cable access, foundation dimensions and external protection with the installation team.
Before releasing manufacture, approve the data sheet, terminal diagram, general arrangement, accessory list and guaranteed performance schedule. The 37.5kVA page is a selection starting point; the accepted technical documents define the supplied unit.
Agree a skid, timber frame or crate appropriate to the route and handling plan. Support the base, restrain movement, protect bushings and loose accessories, and provide moisture protection appropriate to storage and transport. Keep lifting and center-of-gravity markings visible where applicable. A single packing method is not suitable for every shipment.
Confirm lifting points, unloading equipment, container access and securing arrangements before dispatch. Distinguish equipment net weight from packed gross weight, and equipment dimensions from packing dimensions. Delivery documents should identify the unit, packing list, approved drawings and agreed test records. On arrival, check handling damage, sealing condition, accessories and document completeness before installation.
The agreed inspection and test plan defines manufacturing checks, acceptance criteria and delivery records. Review core and coil assembly, internal lead support, insulation clearances, terminal identification, tank condition, coating and fitted accessories. Special tests and third-party witnessing require a defined scope and acceptance basis.
FAT means Factory Acceptance Testing: a contractually agreed acceptance process that may include document review, inspection and witnessing of selected tests. Agree witness points, notice periods and report requirements before manufacture; FAT does not mean every unit receives every type or special test.
Confirm the applicable standard and edition before classifying routine, type and special tests. The following inspection and test schedule is a procurement review list; the signed test plan defines applicability and the records supplied for this unit.
| Inspection or Test | Purpose and Record |
|---|---|
| Visual, dimensional, nameplate and terminal inspection | Compare assembly, markings, cable interfaces and dimensions with approved drawings. |
| Winding resistance | Record resistance and test temperature for winding and connection assessment. |
| Voltage ratio and polarity / connection | Confirm the specified ratio, terminal identification and winding arrangement. |
| No-load loss and excitation current | Record core-related performance under the agreed test conditions. |
| Load loss and short-circuit impedance | Record winding-related losses and impedance with the specified temperature reference. |
| Applicable insulation tests | Verify the agreed dielectric withstand requirements; classify impulse and other tests under the selected standard. |
| Tank sealing inspection | Check the sealing condition of the liquid-filled tank by the agreed method. |
| Fitted accessory functional checks | Check only installed switches, indicators and other applicable accessories. |
Supply compatible household service groups through underground feeders. Confirm diversified demand, secondary service arrangement, load balance and utility protection requirements.
Serve single-phase lighting, refrigeration and general services where the load schedule fits 37.5kVA. Check compressor starting current, harmonics and future expansion.
Provide single-phase service for farm buildings, lighting and compatible equipment. Check motor starting, cable length and corrosion exposure; a single-phase unit does not directly supply three-phase motors.
Compatible single-phase loads whose diversified demand, starting duty and operating conditions fit the rating. At 0.8 power factor, 37.5kVA corresponds to 30kW before considering application-specific allowances.
It provides 50% more rated apparent-power capacity. It is not automatically a direct replacement: voltage, protection, cable ratings and foundation interfaces must also match.
Specify the utility system voltage, required winding voltage and secondary service arrangement. Voltage combinations are subject to engineering confirmation; a capacity rating does not define them.
Both can provide single-phase distribution service, but pad-mounted units use a ground-level enclosure and underground cable interfaces. Pole-mounted designs use overhead mounting and different installation interfaces.
A single unit does not directly supply a three-phase load. Any banked arrangement or alternative transformer requires a separately engineered system design.
Provide altitude, ambient range, coastal exposure, flood risk and local utility requirements. Winding material, fluid, coating and accessories can then be reviewed for the proposed design.
Agree the standard, routine-test records, drawing package and any witness FAT or special-test scope before ordering. Test categories and acceptance criteria depend on the selected standard.
Send the load schedule, voltages, frequency, utility specification, feed layout, cable connector requirements, site conditions and foundation drawing. Confirm protection coordination and grounding responsibilities.
37.5kVA Single Phase Pad Mounted Transformer