ESAB LAF 631, Instruction Manual, Page: 12 / 20

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4 Connection in Parallel Using Six-Thyristor Operation
In this case the Master/Slave welding power sources are connected to the mains by
way of six thyristors (three in each welding power source). This results in softer
welding current as the phase shift is 60
°
instead of 120
°
.
S
Connection of Slave using the six-thyristor effect. Note that the primary
winding of the Slave is reversed.
S
The phase shift goes down from 120
°
to 60
°
, see the diagrams below.
S The following sine-wave diagram shows the equalising effect obtained when
using inversion of the Slave transformer.
The requirement is that the welding power sources are of the same size, and that it
is possible to shift the input and output on the primary side of the main transformer.
This is easily done on LAF 1001, 1251 and 1601, whereas it is more complicated on
LAF 631, as the winding of the transformer is connected directly to the main
contactor.
GB