Warning:
Lethal voltages are generated from this circuit. Construction by inexperienced individuals is dangerous.
This Inverter is now complete. The process of development was to create a 230v 50hz clean sine wave from a variable 18v to 56v wind generator output for use with up to approx 750w load. Circuit development is based on a sinusidal pulse width modulated wave driving a bifilar wound ferrite transformer. Regulation feedback signals will support variable loading up to 56v input. A converter takes variations of the supply voltage to create a load variable 34v -50v input for the inverter. Safety features are incorporated to shut down circuit under abnormal conditions such as excessive driver heat sink temperatures or short circuit load conditions. Output sync'ing to 230v 50hz grid input signal is incorporated with current controlled grid tie loading.
This circuit is freeware for none business use. (Updated Aug 2010)
Design Criteria :
1) Inverter nominal output 230v 50Hz pure sine wave, voltage regulated and/or current regulated grid tie loading.
2) Converter inputs from about 18v wind generator to 56v for regulating the Inverter output.
3) Power output up to about 750w (This is ambient temperature dependant and transformer wire gauge used.)
4) 25.6kHz PWM transformer power transfer for high efficiency and sine modulation.
5) Over/under voltage circuit protection..
6) Driver FET Transistor overload protection (Transformer drive current limit and shutdown)
8) Lost Hz and Short Circuit output protection.(Detects absence of either/both output half Hz)
9) Heat sink overheat protection (Thermal cutout)
10) Zero crossover detection at all output power On/Off (Prevents large output back emf spikes)
11) Current regulated grid tie loading as a function of generator input supply.
Reference Docs : InvTxfr.txt PC90TDK.pdf TransDesign.pdf U93LargeFerriteCores.pdf U93U73Cores.pdf
Finished Circuit : Inverter6.dsn This needs TinyCad to open the files available from: http://tinycad.sourceforge.net
Finished PCB: Inverter6.fpc This needs FreePCB to open file available from http://www.freepcb.com. Many thanks to Bruce Parham & Allan Wright.
Details: circuits.html Inverter_User.doc topcopper.grb bottomcopper.grb bottom soldermask.grb top soldermask.grb topsilk.grb drillfile.drl