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SF-M 3750/4500
YAWEI
The SF-M-3750/4500kVA 13.8kV 480Y/277V Three Phase Oil Immersed Power Transformer is designed for high-capacity power transformation in 60Hz electrical systems. With a rated capacity of 3750/4500kVA, the transformer converts 13.8kV medium voltage to a 480Y/277V low-voltage system, making it suitable for large industrial facilities, commercial power systems, infrastructure projects, and other applications requiring substantial 480V three-phase capacity.
The transformer uses an oil immersed construction for electrical insulation and thermal management. Its Dyn1 vector group provides the specified phase relationship between the high-voltage and low-voltage windings, while the 6% impedance is an important parameter for coordinating voltage regulation, short-circuit calculations, and downstream protection.
The voltage regulation arrangement includes ±4 × 2.5% taps, allowing the transformer ratio to be adjusted according to the specified operating voltage requirements. The cooling configuration can be arranged for KNAN/KNAF operation, providing different thermal operating conditions according to the required loading and project design.
With a 13.8kV primary and 480Y/277V secondary, this transformer is particularly relevant to electrical systems where 480V distribution is used for large motors, HVAC equipment, manufacturing machinery, commercial facilities, and other high-power loads.
The transformer is designed with 3750/4500kVA capacity ratings, providing flexibility for electrical systems with different continuous loading requirements.
The dual-rating arrangement can be coordinated with the project's normal operating load, available cooling mode, load profile, and future capacity requirements.
For large facilities using 480V distribution, this configuration provides a substantial transformation stage between the incoming 13.8kV medium-voltage network and the downstream low-voltage system.
The final continuous rating and corresponding cooling condition should be confirmed according to the approved technical specification.
The transformer converts 13.8kV medium voltage to 480Y/277V, a voltage configuration widely used for three-phase electrical distribution and large commercial or industrial loads.
The 480V line-to-line system can supply equipment such as motors, HVAC systems, pumps, compressors, manufacturing machinery, and other three-phase loads, while the 277V line-to-neutral voltage can serve suitable lighting and auxiliary circuits.
This voltage arrangement allows the transformer to function as a central supply point between the medium-voltage utility or facility network and downstream 480V distribution equipment.
The oil immersed design uses insulating oil around the active parts to provide dielectric insulation and transfer heat generated during transformer operation.
For a transformer in the 3750/4500kVA class, thermal management becomes an important part of continuous operation.
The cooling system can be configured for KNAN/KNAF operation, allowing the transformer to operate under the specified natural and forced-air cooling conditions.
The tank, radiators, fans where applicable, bushings, conservator components, and other cooling-related equipment can be engineered according to the required operating conditions.
The 480Y/277V secondary configuration provides two commonly required voltage levels within a three-phase electrical distribution system.
The 480V phase-to-phase supply can be used for large three-phase equipment, while 277V phase-to-neutral power can support compatible single-phase loads.
This makes the transformer suitable for facilities where industrial equipment, building services, lighting systems, and other electrical loads share the same low-voltage distribution architecture.
Final downstream utilization should always be matched with the actual equipment ratings and the project's electrical distribution design.
The Dyn1 vector group defines the winding connections and phase displacement of the transformer.
The high-voltage winding is connected in delta, while the low-voltage winding is connected in star with the neutral brought out. The clock notation “1” identifies the specified phase displacement between the two winding systems.
Before installation or parallel operation, the vector group should be checked against the upstream and downstream network, grounding arrangement, protection system, and other transformers operating within the same electrical system.
The transformer is specified with an impedance of 6%.
Impedance affects both voltage regulation under load and the prospective short-circuit current on the secondary side.
For a high-capacity 13.8kV to 480Y/277V transformer, the 6% impedance should be considered together with the available fault level, downstream switchgear interrupting rating, feeder configuration, relay settings, and voltage-drop requirements.
This parameter should therefore be coordinated with the overall electrical study rather than evaluated independently.
The transformer is designed with a ±4 × 2.5% tap arrangement, providing multiple voltage adjustment positions around the rated primary voltage.
Tap selection allows the transformer ratio to be matched more closely with the actual incoming system voltage and required secondary operating voltage.
The appropriate tap position should be selected according to the approved operating conditions and transformer documentation. Tap changing must only be performed using the method and under the conditions specified for the installed tap changer.
The transformer can be equipped with monitoring and protection components appropriate to the project's electrical protection scheme.
Depending on the final configuration, equipment may include:
Oil temperature indicator
Winding temperature indicator
Oil level indication
Pressure relief device
Buchholz relay where applicable
Cooling fan monitoring
Alarm and trip contacts
Grounding terminals
Transformer protection interfaces
Remote monitoring interfaces
Communication functions where specified
Other substation monitoring equipment
The final accessory package should be selected according to the customer's technical specification, installation environment, protection philosophy, and applicable standards.
>> Technical Parameters
| Type | Three Phase Oil-immersed Distribution Transformer |
| Model | SF-M 3750/4500 |
| Installation | Outdoor |
| Altitude | ≤1000m |
| Rated Power | 3750/4500KVA |
| Cooling Method | ONAF |
| Primary Voltage | 13.8KV |
| Secondary Voltage | 480V or others |
| Rated Frequence | 50/60HZ |
| Insulation oil | Mineral oil |
| Tapping Range | ±2×2.5%/±5% |
| Temperature rise℃) | 65 |
| Connection Group | Dyn11/Yyn0 |
| Total weight(kg) |
The 3750/4500kVA 13.8kV to 480Y/277V transformer can serve large manufacturing plants, production facilities, processing plants, and industrial campuses.
It can supply 480V switchboards, motors, pumps, compressors, HVAC systems, production machinery, and other high-power equipment.
Large commercial facilities may require both 480V three-phase power and 277V single-phase distribution.
The 480Y/277V secondary arrangement can support compatible HVAC, mechanical, lighting, and building-service loads through the facility's low-voltage distribution system.
Manufacturing facilities with substantial motor and equipment loads can use a 13.8kV to 480V transformation stage to distribute electrical power closer to the production equipment.
The transformer capacity can be coordinated with the plant's connected load, demand profile, and future expansion requirements.
Large technology facilities can require high-capacity electrical infrastructure for cooling systems, power distribution equipment, auxiliary systems, and other continuous loads.
Where the electrical design specifies a 13.8kV incoming supply and 480Y/277V distribution, this transformer configuration can be considered as part of the facility substation.
The transformer can also be applied to transportation facilities, water and wastewater facilities, institutional infrastructure, large utility installations, and other projects requiring substantial 480Y/277V distribution capacity.
The actual suitability depends on the project's load characteristics, environmental conditions, protection requirements, and applicable electrical standards.
For utility-connected or privately operated substations, the transformer can provide the interface between a 13.8kV medium-voltage network and the facility's 480Y/277V distribution system.
The final transformer design should be coordinated with the utility interconnection requirements and the customer's protection and metering scheme.
The following information provides general operating guidance for the SF-M-3750/4500kVA 13.8kV 480Y/277V oil immersed transformer. Installation, commissioning, testing, and maintenance should be performed by qualified electrical personnel according to the manufacturer's documentation and applicable safety requirements.
Use appropriate lifting and transportation equipment when moving the transformer.
After delivery, inspect the unit for transportation damage, oil leakage, damaged bushings, deformation, loose components, and missing accessories.
Verify the nameplate information and compare the delivered equipment with the approved packing list and technical documents.
Install the transformer on a properly designed foundation capable of supporting the equipment weight.
Provide sufficient working clearance around the transformer for inspection, cooling, operation, and maintenance.
The installation area should also provide suitable grounding, drainage, ventilation, fire protection, and access according to the project requirements.
Before energization, inspect the oil level and examine the tank, radiators, bushings, valves, conservator components, temperature indicators, and pressure relief equipment.
Check for visible oil leakage or mechanical damage.
Any abnormal condition should be corrected before commissioning.
Connect the 13.8kV high-voltage side and 480Y/277V low-voltage side according to the approved electrical drawings.
Check:
Phase identification
HV and LV terminal connections
Neutral connection
Grounding
Cable or busbar connections
Protection wiring
Monitoring circuits
Tap position
All electrical connections should be inspected and tightened according to the applicable installation procedure.
Before energization, verify the operation of the transformer protection and monitoring circuits.
Depending on the installed configuration, this may include temperature alarms, oil level alarms, pressure protection, Buchholz protection, cooling fan control, and remote monitoring interfaces.
Protection settings should be coordinated with the facility's electrical protection system.
Confirm the tap position before energization.
The transformer is specified with ±4 × 2.5% voltage adjustment, and the selected position should correspond to the required system voltage.
Do not change the tap position unless the applicable transformer design and operating procedure specifically permit the adjustment under the required operating condition.
After all commissioning checks have been completed, energize the transformer according to the approved site procedure.
During initial operation, observe:
Primary voltage
Secondary voltage
Load current
Oil temperature
Winding temperature
Oil level
Cooling system condition
Protection alarms
Abnormal sound or vibration
The transformer should be monitored carefully during the initial loading period.
The cooling arrangement may include KNAN/KNAF operating modes according to the transformer design.
Where forced-air cooling equipment is installed, verify fan operation, control signals, alarms, and temperature-based switching before placing the transformer under the specified load.
Cooling equipment should remain unobstructed and properly maintained.
During normal operation, periodically monitor the transformer's electrical and thermal conditions.
Particular attention should be given to changes in load current, oil temperature, winding temperature, oil level, abnormal noise, vibration, and protection alarms.
Operating values should remain within the limits specified in the manufacturer's documentation.
Maintenance intervals should be determined according to transformer loading, operating environment, manufacturer's recommendations, and applicable maintenance standards.
Typical maintenance activities may include:
Visual inspection
Oil level inspection
Insulating oil testing
Bushing inspection
Grounding inspection
Cooling system inspection
Temperature device testing
Protection system testing
Electrical connection inspection
Tap mechanism inspection where applicable
Before any internal inspection or maintenance, the transformer must be fully isolated, de-energized, discharged, and grounded in accordance with the applicable safety procedure.
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