Autotransformer Use

Er, because of the disadvantage?

Ground loop.

Cost is another, in fact all the advantages you have listed are in fact disadvantages against the autotransformer when comparing it to standard 3 phase transmission and distribution transformers.

Another example is trying to compare an adjustable spanner to a regular spanner., inferior in virtually every way except for convenience (same with autotransformers).

Thank you.Ground loops are formed when loadside have more ground points and there is a potential difference right.This can be avoided by using an isolation transformer,but how it is related to autotransformer?Is mutual conduction a problem where electical isolation is not needed? Can you tell me how these advantages become disadvantage during power transmission and distribution?

Hi Hithuanand,

You seem to be aware of part of the story, please let me explain the complexities to you;

• For an auto T/F the insulation should be of a better class, for example in a two winding transformer when you can use A-class insulation, in the Auto T/F you must select E-class or better insulation.
• Cost of insulation when the transformation ratio is high goes high which nullifies any savings in copper.
• For an Auto transformer the calculated short circuit level is appreciably higher than a two winding T/F.

Due to lack of isolation between windings, higher cost of insulation and higher short circuit currents the auto transformer is only used in transmission substations under the criteria that the transformer has low ratio of transformation say 1:2.
Please be aware not to consider using an Auto Transformer at the steel factory you work since cost of replacement of existing circuit breakers with a high short circuit capacity CB's alone will consume the entire budget.

Thank you sir.

hi,

• To reduce the noise level, Auto transformers were widely used, which will provide clean power to the load.
• Auto transformers are frequently used in power applications to interconnect systems operating at different voltage classes.
• In audio applications, tapped auto transformers are used to adapt speakers to constant-voltage audio distribution systems, and for impedance matching such as between a low-impedance microphone and a high-impedance amplifier input.

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