!: Three Phase Generators - Their History and Why They Work So Well

The three phase generator you need for your workshop has a long and very interesting history. They were invented just a few decades after electricity was first controlled and managed in machines by Faraday in the 1820s. From that time until the middle of the 1900s the changing of direct current to alternating current was achieved using rotary generators.

Early on these converters used a synchronous or induction AC motor connected up to a generator. The link was made in such a way that the dynamo's commutator reversed it's shiny connector plates at precisely the right time to generated direct current.

This worked perfectly well, although there is always room for improvement and after some time the synchronous converter was developed by enterprising engineers. In these advanced converters the windings on the motor and generator were combined in one armature. At one end this was gripped by slip rings, at the other a commutator was positioned and both relating to just one field frame. As a result alternating current went in and direct current went out.

About mid-way through the period we are describing, in the early 1900s, vacuum tubes or tubes packed with gas were adapted and used as switches in these converter's circuits.

The rotary generators of these machines were often called M-G sets. Something interesting is possible with these sets. The direct current can be said to be generated independently from the alternating current. This is distinct from the current produced by synchronous converters where it can be said that they output alternating current that has been "rectified" by a physical mechanism. So, if you put in place the correct auxiliary and controllers, an M-G set rotary converter can be made to turn "backwards" ie., turning AC into DC. This is where we get our modern term inverted converter.

From this elementary beginning we now have phase converters that will take direct current from batteries, solar panels or fuel cells and turn that into alternating current running at any voltage. So equipment designed to be plugged into a mains power socket can run on there storage devices. Or conversely they can be rectified to output direct current at a particular voltage.

The humble three phase generator is a reliable workhorse.