Hot to reduce 120 vac to 82 vac, 300 watt load

Externet said:
Use 120VAC wiring two lamps in series and evaluate if performs reasonably well.
Click to expand...
Using typical tungsten lamp resistance variation with voltage, that would give only about 188W per bulb which is likely insufficient for a bright, white light.

But three bulbs in series with a 240V supply would give 80V per bulb which should work fine.
 

@mobus1

Find a 120V to 35 or 36 volt transformer 300VA

put the sec wdg in series with the primary ( primary connected to 120V ac ) and measure the output - if it is not 120 - 35 = 85V

then reverse the 35V connection until you do get 85V end to end ( this is called a series opposing connection )

Voila - job done !

{ you can do similar with a 120: 48V transformer, but this time connect in series aiding to get 168V, then remove the 120 and apply it to where the 168V was - you will now get 85Vac across the 120V wdg }

good luck
 

This was the idea of post#2, but thankfully you eleborated it for the OP.
With a 300W (indeed they are specified in VA) you may operate two projectors.

****
Serializing bulbs:
due to their PTC behaviour and production tolerances, the voltages don´t divide well. Expect darker/brighter bulbs with reduced lifespan.

Klaus
 

obviously a purpose built auto-transforrmer would be better - and smaller ! but the OP said it would be too expensive.
 

You must log in or register to reply here.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…