The electricity generated by most wind turbine generators is alternating current (AC). To use this to charge batteries or power most lighting and devices directly, it must be rectified into direct current (DC).
The simplest (full wave) bridge rectifier is made up of just four diodes (components which allow electricity to flow in just one direction). The diagram below (taken from our Introduction to Bridge Rectifiers) shows how the four diodes are wired together and also shows how electricity flows through it as the current alternates.
Three Phase Bridge Rectifiers
Typically wind turbines do not generate single phase AC (displayed in the above example), but instead generate multi-phase AC – usually three-phase AC electricity. To better understand the basic principles of three phase electricity please click here.
Therefore, more diodes are required to rectify the three phases of electricity – in fact six are required and must be wired up as shown in the diagram below.
Click here to view our article Three Phase Bridge Rectifier which has details of commercially available three phase bridge rectifiers of different sizes suitable for use in renewable projects and permanent wind and hydro power installations.
Why Make Your Own Bridge Rectifier?
It is possible to purchase complete bridge rectifiers cheaply with current ratings from below 1 Amp to as much as 35 or 50 Amps. To make a three phase bridge rectifier is a simple case of wiring them together and then to each of the three phases of generated electricity. Click here to find out how to make a three phase bridge rectifier in this way.Pictured above is an example of a 35A bridge rectifier (available for sale through this website). Bridge rectifiers rated above 35A or 50A suddenly become very expensive. Therefore if your wind turbine has a total maximum output current of more than 25-30 Amps, it is worthwhile making your own bridge rectifier with high power rated diodes wired as shown above but fitted to a suitably large heatsink.
High Current High Voltage Diodes
Diodes are available in a massive range of voltages and currents. Here is a list of a few example diodes which can be used in bridge rectifiers for high current applications:
1N4045 Rectifier Diode – rated up to 275 Amps at voltages of up to 100 Volts. These are particularly suitable for 12V wind turbines which will not exceed 100 Volts, but may generate high currents. The 1N4045 datasheet (PDF 99 kB) can be downloaded here.
MBR7030WT Schottky Power Rectifier – rated up to 70 Amps and 30 Volts. These are again suitable for many 12V wind turbines and are available for just a couple of pounds each. MBR7030WT datasheet(PDF) is available here.
DD171N14K Dual Power Module – rated at up to 1400 Volts and 171 Amps. These would be suitable for almost any domestic wind turbine.
Any specific high current diode can be hard to find when you want one, so we have found that over the years the best way to find suitable components is simply to do this ebay search Schottky Rectifier and have a look through the few hundred items listed. Most will be <10A rated diodes, but these are mixed in with the odd 60A diode or 100A diode etc.