selection of transformer

Thread Starter

vead

Joined Nov 24, 2011
712
hiiiiiiiiiiii

i need transformer for 12v dc 2a
can i use this formula for transformer secondary voltage

Vsec(rms) = (Regulated DC + Regulator Drop + Ripple voltage + Rectifier Drop)/√2

where, regulated dc=12vdc
regulator drop= 3v
ripple voltage=1v
rectifier drop=1.4v

Vsec(rms)=12.30ac

if any mistakes please correct me
 

k7elp60

Joined Nov 4, 2008
555
You are pretty close. I would use a standard transformer that has a secondary voltage of 12.6 volts. But the transformer must have a secondary current rating of 3.3 amps or you will have excess heating caused by brute force filtering. With brute force filtering(bridge rectifier to filter capacitor then regulator) the charging current will be load current/0.6= 2/.6 or 3.33A. I think the closest off the shelf transformer would be 4A secondary.
 

Thread Starter

vead

Joined Nov 24, 2011
712
hii

i cann't understand
how can i calculate current rating of transformer
 
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