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 240v 50hz clean sine wave from a variable 20v to 50v wind generator output for use with a 1.0kw 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 48v input. A converter takes variations of the supply voltage to create a constant 48-50v 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 syncing to a grid input signal is incorporated which provides a volt free relay contact for grid tie isolation option. This circuit is freeware.
Successful preliminary tests have been carried out as far as the output stage, loading results to be advised.(Updated April 2010)
Design Criteria :
1) 48v Inverter nominal input for 230v 50Hz pure sine wave nominal output.
2) Converter from about 25v generator in to 48v constant output.
3) Power output in excess of 1.0 kw (This is ambient temperature dependant)
4) 25.6kHz PWM transformer power transfer for high efficiency and sine modulation.
5) Overvoltage circuit protection at 56v with a 65v limit which will disconnect generator from system.
6) Undervoltage protection at 22v with hysteresis to prevent 'hunting' due to generator fluctuations.
7) Drive FET Transistor overload protection (Transformer drive current limit and shutdown)
8) Lost Hz and Short Circuit output protection.(Detects absense 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) Over/Under logic supply voltage protection (in case of circuit failures)
12) Grid syncing with volt free relay contact closure when full synchronised.
This project has grown like Topsy but is now essentially complete for use in the Scottish Hebrides as a supplimentry power source.
Reference Docs : InvTxfr.txt PC90TDK.pdf TransDesign.pdf U93LargeFerriteCores.pdf U93U73Cores.pdf
Finished Circuit : Inverter5.dsn This needs TinyCad to open the files available from: http://tinycad.sourceforge.net
Details: circuits.html Inverter_User.doc