Autotransformers / Isolating Transformers

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Autotransformers and isolating transformers are two types of transformer suitable for special applications. An autotransformer is a one-winding transformer, with both primary and secondary circuits sharing a single winding. The single winding saves copper, compared to conventional two-winding transformers, especially when the ratio of the transformer is low. This makes the transformer lightweight, smaller in size and more cost-effective. The reduction of copper also results in less ohmic loss and core loss, making autotransformers more efficient than two-winding transformers. Autotransformers are used to compensate voltage drops, and thereby boost supply voltage in distribution systems. Autotransformers have better voltage regulation capabilities, as the voltage drop in resistance single winding reactance is less. Isolating transformers transfer electrical current from an alternating current (AC) source to equipment or a device, while keeping the device itself isolated from this power source. These transformers adopt the galvanic isolation method, where the circuits are isolated. The isolation transformer has copper coils wound around each other, with both coils supplied by their own power source. The circuits are separated either with an induction loop or by decreasing the AC voltage before it reaches the circuit. The isolation of the device from the power source protects the device itself from stray current, surges and electrical noise. It also protects users against electric shocks.