Circuit for converting 120v - 30a AC to 96v DC at 30 amps

Thread Starter

systemroot

Joined Jan 3, 2021
10
I plan on making a gasoline powered ebike... The gas generator is 3600w and makes 30 amps at 120v AC.
I plan on using a 3kv variac to convert that to 90 V AC. Then bridge rectified to DC using a 200v, 100 amp full bridge rectifier... Then using 2 (63 volts, 100,000uf ) capacitors in series, for a total filter of 50,000uf as they are in series and rating of 126volts... I heard that you got to multiply the 90 volts by the square root of 2 rms, so thats around 130 volts, which is the upper limit of the ebike controller... I just want a smooth DC voltage as long as if its between 90v and 130v (despite title saying 96v).
The problem is i need a pure DC source and my calculations on ripple for C = I / (2 x f x Vpp) , says C = 30 amps / (2 x 60hz x 0.1v ripple) = 2.5 Farads... That is a a big difference from the 50,000 uf... Any help / suggestions here. Thanks
 

sghioto

Joined Dec 31, 2017
2,363
I remember an old rule of thumb for a full wave bridge was 2000uf per amp needed. So 50/30 = 1667uf per amp, probably close enough.
 

Thread Starter

systemroot

Joined Jan 3, 2021
10
Why? It is bound to be heavier, bulkier, and less efficient than a gas powered bike or a battery powered E-bike. What advantage do you see for your design that outweighs the disadvantages.

Bob
Laws... Ebikes have range problems... A ebike running off a gen is a ebike... A bike running of a gas engine is a motorcycle and requires license / registration / etc etc... Yet an ebike with a generator trailer is an ebike and follows ebike laws and has unlimited range... The unlimited range is a key thing as most ebikes at 40mph only go like 40 mile range tops which is not much... Also i looked at a online calculator for ebike wattage and speed and the extra weight only subtracts like 1 mph off of top speed... The generator is 100lbs and i weigh 130, so it would be the same as a heavy set 230lb guy riding my bike.
 

Thread Starter

systemroot

Joined Jan 3, 2021
10
Is the output a sinewave?
i dont have a scope sorry... i am 18 and budgets are low. A youtuber had a scope and said it was ok, and im willing to risk it. My question is if i put a capacitor in parrallel to the mains AC, will that filter the sinewave for the switchmode supply... i maybe totally wrong here lol, i head that switching supplies have input filter capacitors, so i figure if i have some ones added parralel to mains, it will help out the supply...
 

sghioto

Joined Dec 31, 2017
2,363
Looks OK. They mention operating a computer which normally has a switch mode power supply.
Did notice you would need to wire the variac to both 120 volt outlets.
 

Thread Starter

systemroot

Joined Jan 3, 2021
10
Looks OK. They mention operating a computer which normally has a switch mode power supply.
Did notice you would need to wire the variac to both 120 volt outlets.
i decided to screw the variac... I am just going to have 2 120 volts switchmode supplies that make 48 volts off aliexpress and put them in series.
 
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