When machine voltage does not match the local grid, an autotransformer is the most common solution. Using a single winding, it is smaller, lighter and cheaper than an isolation transformer of the same rating.
ONS Enerji manufactures autotransformers to your required voltage ratio, power and construction (single/three-phase, open or enclosed). Isolation requirements are assessed with you at the start of every project.
How does it work?
In an autotransformer part of the winding serves both input and output. The output is drawn from an intermediate point (tap) on the winding; the position of that tap sets the voltage ratio.
Because a large share of power is transferred directly rather than magnetically, losses are low and efficiency is high. For the same reason input and output are electrically connected, so an autotransformer cannot be used where isolation is mandatory.
Key features
Applications
- Adapting imported machines to local supply (e.g. 220 ↔ 380 V, 110 ↔ 220 V)
- Motor starting and voltage matching applications
- Compensating voltage drop on long lines
- Industrial machinery and equipment supply
- Local-voltage matching for machines exported abroad
Technical selection parameters
| Parameter | Options / typical range |
|---|---|
| Phase configuration | Single-phase or three-phase |
| Voltage ratio | E.g. 380/220 V, 400/230 V, 220/110 V or custom |
| Power | Per project (VA – kVA) |
| Galvanic isolation | None (input and output are electrically connected) |
| Efficiency | Generally higher than an isolation transformer of the same rating |
| Construction | Open or enclosed; protection class per environment |
| Winding material | Defined by technical specification |
| Cooling | Natural (AN) or fan-assisted |
This table shows general characteristics of the technology and the parameters defined at order. Exact values are confirmed per project and in the datasheet.
How to choose the right unit
- Define input and output voltage, number of phases and neutral requirement.
- If there is an electric-shock risk or a noise problem, consider an isolation transformer instead.
- State total power and whether duty is continuous or short-time.
- Consider protection design against loss of neutral.
Frequently Asked Questions
01What is the difference between an autotransformer and an isolation transformer?
An autotransformer uses one winding shared by input and output; it is cheap and efficient but gives no galvanic isolation. An isolation transformer has two electrically separate windings, which provides safety and noise filtering.
02Can an autotransformer both step down and step up voltage?
Yes. Depending on the tap position it can raise or lower voltage. The ratio is defined per project.
03Can an autotransformer be used in wet environments?
Wet or high-shock-risk environments require isolation. In such areas an isolation transformer should be used instead of an autotransformer.
04Do you manufacture autotransformers with custom voltage ratios?
Yes. We build to your input/output voltage, phase count and power. You can send your details through the quote form.