The Australian electronics magazine, Silicon Chip, has just published a design for a variable speed inverter for driving three phase motors, as well as some types of single phase motors, up to 1.5kW motor output. The first installment appears in the April 2012 edition, with a second part to follow. The design is based around the Australian electricity supply, which is nominally 230V at 50 Hz, which I presume is compatible with that in the UK. The design uses a microprocessor to control three insulated gate bipolar transistor (IGBT) half bridges, all of which are contained in a single integrated module. The half bridges are used to switch the rectified and filtered mains supply at 16 kHz in clever ways to produce the necessary waveforms, amplitudes and phasing. The device has variable soft starting but apparently no jog facility. The article provides a detailed description of the circuit operation and discusses the issues that arise in driving various types of single phase motors. The magazine article suggests a ball park price of “a couple of hundred A$” (approx £130) for the required parts. Usually various local kit suppliers who advertise in the magazine will offer kits of parts for most Silicon Chip projects fairly soon after publication and I would expect that will likely occur with this one (eg Jaycar & Altronics). Anyone requiring further information could check out http://www.siliconchip.com.au. I have no connection with Silicon Chip other than as a long term reader nor with the kit suppliers mentioned except as an occasional customer.