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In electrical engineering, an autotransformer is an electrical transformer with only one winding. The "auto" (Greek for "self") prefix refers to the single coil acting alone. In an autotransformer, portions of the same winding act as both the primary winding and secondary winding sides of the transformer. In contrast, an ordinary transformer ...
This basic principle explains the source of the destructive transient voltage in the Korndörfer motor starter apparatus. A further transient problem is that with a single coil construction and a star switch, the autotransformer acts as a step-up transformer during the <5 microsecond period at contact separation of the Star point switch.
A transformer or autotransformer can be used; (auto)transformers are inherently reversible, so the same transformer can be used to step the voltage up, or step it down by the same ratio. Lighter and smaller devices can be made using electronic circuitry; reducing the voltage electronically is simpler and cheaper than increasing it.
A leakage transformer, also called a stray-field transformer, has a significantly higher leakage inductance than other transformers, sometimes increased by a magnetic bypass or shunt in its core between primary and secondary, which is sometimes adjustable with a set screw. This provides a transformer with an inherent current limitation due to ...
For example, a 24 VCT transformer will measure 24 VAC across the outer two taps (winding as a whole), and 12 VAC from each outer tap to the center-tap (half winding). These two 12 VAC supplies are 180 degrees out of phase with each other, measured with respect to the tap, thus making it easy to derive positive and negative 12 volt DC power ...
In practice, it is necessary to allow a small interval between powering the transformer one way and powering it the other: the “switches” are usually pairs of transistors (or similar devices), and were the two transistors in the pair to switch simultaneously there would be a risk of shorting out the power supply.
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Cutaway view of an LVDT. Current is driven through the primary coil at A, causing an induction current to be generated through the secondary coils at B.. The linear variable differential transformer (LVDT) – also called linear variable displacement transformer, [1] linear variable displacement transducer, [2] or simply differential transformer [3] – is a type of electrical transformer [4 ...