This document discusses the effect of source impedance on the performance of converters. It states that the output voltage of single-phase and three-phase full converters is reduced if the source has resistive impedance, with single-phase output reduced by the current through the source resistance and three-phase output reduced by twice the current through the source resistance. If the source impedance is inductive, the incoming and outgoing SCRs conduct together during commutation, resulting in the output voltage being equal to the average of the conducting phase voltages for single-phase converters and the average of two phase voltages for three-phase converters.

2. Effect of source impedance on the
performance of converters
On the assumption of output current
instantaneously change from outgoing
SCR to incoming SCR, the out put
voltage of
Single phase full controlled converter Vout=
Three phase full controlled converter Vout=
This equation is applicable when source
has no source impedance

3. But generally source has internal
impedance
It may be resistive or inductive
If source impedance is resistive
Single phase converter output is
reduced by Iors
And three phase converter output is
reduced by 2Iors

4. If source impedance is pure inductive and load
inductance is large –output ct is constant
The source inductance cause incoming and
outgoing SCR conduct together
During commutation period, the output voltage is
equal to average value of the conducting phase
voltages
Single phase full converter the load voltage
is “0”
 Three phase full converter the load voltage
is “(Va+Vb)/2”
Overlap period – Period at which all SCR are
conducting
Angle corresponding to this period is often called
overlap angle or commutation angle

5. 1Φ full converter
with source
inductance
1Φ full converter with
source inductance
Equivalent Circuit

6. Output voltage and Current Wave Form

7. The output Current is
The average Output Voltage
Vo
From
Io
Substitute this value
in Vo

8. The average output voltage is decrease in
response of increasing source inductance