When we choose a transformer, you may be always asked one question, do you need an isolation transformer or an auto transformer?Here I am going to talk about the difference and similarity of an isolation transformer and an auto transformer.
Definition Of Isolation Transformer And Auto Transformer
The isolation transformer is an electrical transformer with a primary and secondary coil winding.These winding are separated by insulation.This insulation limits the the risk of electrocution when the active parts and earth are touched simultaneously.
The auto transformer is an electrical transformer with only one coil winding.Its low-voltage coil is also a part of the high-voltage coil.’Auto’ refers a single coil acting alone with a tap in the middle of winding as a common point of high-voltage winding and low-voltage winding rather than any kind of automatic mechanism.
Operation And Purpose Of Isolation Transformer And Auto Transformer
The primary purpose of an isolation transformer is to isolate the circuit.The capacity coupling between the two winding needs to be paid attention while designing and manufacturing an isolation transformer. Capacitance between primary and secondary winding would also couple alternating current (AC) current from the primary to the secondary.
Auto transformer is used to regulate the voltage of transmission lines and can be used to transform voltages.With only one winding, an auto transformer adjusts the voltage automatically according to load. These transformers call for AC currents to operate correctly and will not function on direct current.
Application
Isolation transformers are mainly used in the occasions of safety, isolation,small leakage current,purified power, interference reduction and the elimination of third harmonic.It is applicable in the ac circuit of from 50Hz to 400Hz and below 1000V. Being widely used in lighting,machine tool electric appliance, Electrical equipment, medical equipment and rectifying device.
Auto transformers are widely used in high voltage power network, becoming voltage conversion device to transfer important electric energy.Auto transformers are mainly used in the occasions of power system, industrial and mining enterprises, transportation, posts and telecommunications departments, scientific research units and other equipment electricity and other places requiring voltage conversion.
Advantage
Isolation transformer
●Better power quality
●Noise reduction
●Reduces surges
●Safety
Auto transformer
●Cheap and more efficient
●Less leakage inductance between primary and secondary
●Simple construction
●Smaller footprint for same VA rating
How to distinguish them in appearance
The primary and secondary of isolation transformer are on different winding.
The primary and secondary of auto transformer are on one winding.
Externally if we can see the input and output leads of the transformer are independent of each other and there is no common lead, it is an isolation transformer. Whereas it is an auto transformer.