
AC power generation
Before the adoption of alternating current (AC), very large direct-current dynamos were the only means of power generation and distribution.
Large power generation dynamos are now rarely seen due to the almost universal use of alternating current for power distribution.
AC came to dominate due to the ability of AC to be easily transformed to and from very high voltages and the resultant low power transmission losses when power is distributed over large distances.

Image from Deptford power station
Sebastian Ziani de Ferranti established Ferranti, Thompson [after Alfred Thompson] and Ince in 1882 to market his Ferranti-Thomson [after Sir William Thomson] Alternator.
Ferranti went on to design the Deptford power station for the London Electric Supply Corporation in 1887 using an alternating current system.
On its completion in 1891, it supplied high-voltage AC power that was then 'stepped-down' for consumer use on each street.
This image is of the Ferranti 1000kW alternator (156 rpm) installed and photographed at the Deptford power station in 1895.
We’re upgrading our systems, and this includes changes to our customer and member account log in, MyIET. It’s part of our big picture plan to deliver a great experience for you and our wider engineering community.
Whilst most of our websites remain available for browsing, it will not be possible to log in to purchase products or access services from Thursday, 17 April to Wednesday, 30 April 2025. Our Member Relations team is here to help and for many of our services, including processing payments or orders, we’ll be able to support you over the phone on +44 (0)1438 765678 or email via membership@theiet.org.
We apologise for any inconvenience this may cause and thank you for your understanding.
For further information related to specific products and services, please visit our FAQs webpage.