What is an autotransformer ?

What is a autotransformer?

An autotransformer is an electrical device that can change the voltage and intensity between the input and the output. The transformation ratio is identical between primary (input) and secondary (output) as described below:

Primary voltage x Primary current
=
Secondary voltage x Secondary current

However, unlike transformers, autotransformers cannot isolate two circuits. The primary and the secondary shall be electrically connected to each other. They do not have the protective role of transformers that electrically isolate the primary (input) circuit from the secondary (output) circuit.Compared to transformers, autotransformers are generally much more compact and less expensive but do not provide the same level of security exposing the output network to input network failures. With a transformer, in case of failure (overload or overvoltage) it is the latter that supports them preserving the equipment in outputs.Opting for a autotransformer is not always possible for safety reasons.

OTHER QUESTIONS

• Delivery and installation ?
• What is a transformer ?
• What are typical transformer applications ?
• Who needs an autotransformer ?
• How to choose the right transformer ?
• Can a transformer change the three-phase into single-phase ?
• Can a transformer change the single-phase into three-phase ?
• Can a transformers be used in parallel ?
• Can 60Hz transformers run at 50Hz ?
• What is the regulation of a transformer ?
• Why is impedance important ?