# Semi controlled rectifiers

Discussion in 'General Electronics Chat' started by Tera-Scale, Jun 30, 2012.

1. ### Tera-Scale Thread Starter Active Member

Jan 1, 2011
164
5
Below are the formulas for Vmean of three phase and single phase semi controlled rectifiers;

Single Phase semi-controlled;

$V_{mean}=(\frac{V_{pk}}{\pi})(1+cos\alpha)$

Three phase semi-controlled;

$V_{mean}=(\frac{(V_{rms})3\sqrt{3}}{\sqrt{2}\pi})(1+cos\alpha)$

How can I subtract diode drop (0.7V) and SCR drops (1.2V) separately?

2. ### crutschow Expert

Mar 14, 2008
13,505
3,376
An SCR is a Silicon Controlled Rectifier.

You just subtract the 1.2V forward drop of each SCR and 0.7V from Vpk for each diode that is in the conducting path.

3. ### KMoffett AAC Fanatic!

Dec 19, 2007
2,584
234
I like "semi controlled rectifiers"...you can turn then on, but you can't turn them off.

Ken

4. ### Tera-Scale Thread Starter Active Member

Jan 1, 2011
164
5
So, obviously this depends on the configuration of the diodes and SCRs. For the configuration attached I can just subtract (0.7V+1.2V) from the Vmean at the end. Therefore it is just simple as that. Attached are the formulas I attempted for a practical situation in my country.

http://dc382.4shared.com/doc/3rwHGL1l/preview004.png

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