Transformers in power distribution networks

Why do we need transformers? The answer is simple: impedance. If power losses in electricity distribution networks are to be kept within reasonable limits, then large amounts of electric power have to be transmitted across long distances at the highest feasible voltage. In absolute terms, the higher the trans-mission voltage, the smaller the current and hence the smaller the (resistive) power losses in the transmission cables. But increasing the transmission voltage also reduces a given power loss in relative terms. Whereas a voltage drop of 3 V in a motor vehicle’s 12-volt on-board electrical system is a significant loss, it would hardly raise an eyebrow in a low-voltage dis-tribution network (230/400 V), and certainly wouldn’t impair the function of any load. In a high-voltage network, that same 3-volt drop would be almost immeasurably small. This is why cars will be fitted in future with a more powerful 36-volt battery (generator voltage: 42 V), as many of the secondary and auxiliary functions currently driven by pneumatic or hydraulic systems or driven mechanically by the crankshaft will be electrically powered. The demand for these higher voltage systems is set to grow. There will be a transitional period in which vehicles will have a dual-voltage architecture with a DC-DC converter coupling the two voltage levels. And the coupling of two voltages in the very restricted space of a motor vehicle links in to our main sub-ject of discussion: the coupling of voltages in public and industrial AC and three-phase power networks.