1250kVA Oil-Immersed Transformer: Specifications, Dimensions & Applications
Time：2026-02-26 Auther：ZTelec-www.ztelectransformer.com
The 1250kVA oil-immersed transformer is a popular choice for industrial and commercial power systems. It offers a practical balance between power capacity, size, and cost, making it suitable for many medium to large-scale projects.
If your project requires stable voltage conversion and reliable long-term operation, understanding this transformer’s specifications and installation needs will help you make better decisions and avoid costly mistakes.
Key Specifications You Should Know
A standard 1250kVA transformer comes with a set of core technical parameters that directly affect performance and safety.
Rated Capacity: 1250 kVA, ideal for medium and high load demands.
Primary Voltage: Typically 10kV, 11kV, 20kV, or 33kV, depending on your local grid.
Secondary Voltage: Usually 400V/230V, but can be customized.
Cooling Method: ONAN (natural cooling) or ONAF (forced air cooling for higher loads).
Impedance: Normally 4%–6%, helping limit short-circuit current.
Connection Type: Common options include Dyn11 or Yyn0.
Standards: Designed according to IEC 60076, GB/T 6451, and similar standards.
These parameters determine how efficiently and safely the transformer operates over time.
Typical Dimensions and Space Planning
Before installation, it’s important to understand the transformer’s physical size to plan transportation and layout.
A typical 1250kVA oil-immersed transformer has the following dimensions:
Length: 1900 mm to 2300 mm
Width: 1200 mm to 1500 mm
Height: 1800 mm to 2200 mm
These values may vary depending on the manufacturer and configuration. If combined with switchgear or used in a compact substation, the total footprint will be larger.
Always reserve enough space for maintenance and ventilation during design.
Where Is a 1250kVA Transformer Used?
This transformer capacity is widely used across different industries because it handles large and continuous loads effectively.
In manufacturing plants, it powers production lines, CNC machines, and heavy equipment.
In industrial parks, it distributes electricity to multiple buildings from a central point.
In mining, chemical, and metallurgical industries, it supports high starting currents and harsh working conditions.
In infrastructure projects such as airports, hospitals, and shopping centers, it ensures stable and uninterrupted power.
In solar and wind energy systems, it steps up voltage for grid connection.
Installation Tips for Better Performance
Proper installation is essential for safety and long-term reliability.
Foundation: The transformer weighs around 4 tons, so a strong concrete base is required.
Ventilation: Keep at least 1 meter of space around the transformer for cooling.
Fire Safety: Install in a dedicated transformer room or include oil drainage systems.
Oil Monitoring: Check oil levels regularly and monitor the silica gel breather condition.
Good installation reduces failure risk and extends service life.
Maintenance Made Simple
Routine maintenance helps prevent unexpected downtime.
Check insulation resistance and dielectric performance annually.
Inspect transformer oil quality and replace or treat it if necessary.
Monitor temperature and load conditions to avoid overheating.
Simple preventive steps can significantly improve reliability.
The 1250kVA oil-immersed transformer is a dependable and cost-effective solution for modern power distribution. It combines strong performance, flexibility, and long service life.
By clearly understanding its specifications, dimensions, and usage scenarios, you can design more efficient systems and ensure stable power supply for your project.
If you need accurate sizing, drawings, or pricing, providing your voltage level, load data, and configuration requirements will help achieve a more precise and optimized solution.
