# Semi controlled rectifiers

#### Tera-Scale

Joined Jan 1, 2011
164
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?

#### crutschow

Joined Mar 14, 2008
23,352
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.

#### KMoffett

Joined Dec 19, 2007
2,770
I like "semi controlled rectifiers"...you can turn then on, but you can't turn them off.

Ken

#### Tera-Scale

Joined Jan 1, 2011
164
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.
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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