Applying The Resonance Converter Principle; Measuring And Regulating The Parameters "Welding Current" And "Welding Voltage - Fronius Transpocket 1500 Erdstrom Serviceanleitung, Ersatzteilliste

Complex -
regulation
(3) The output voltage tends towards operating point (4) as a result of the load resistance becoming smaller
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(continued)
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Applying the
resonance
converter
principle
U
DC
Fig.9
A special feature here is the centre-tap of the secondary winding, which determines the
frame potential of the welding voltage.
Positive half-waves are fed to the
winding and one of the two secondary diodes. Negative half-waves are routed to the
socket via the other of the two end-taps and the other secondary diode.
In this way, full-wave rectification is achieved, yet with no need for a space-intensive 4-
diode bridge rectifier, which would also generate increased heat-loss. In keeping with
the series-parallel resonance converter, the capacitor C
resistor (=welding process).
The increase in the output voltage brought about by capacitor C
increase in the load resistance (arc threatens to break) plays a major role in optimising
the welding properties. Furthermore, in order to achieve a perfect welding result and
outstanding welding properties, the welding current and welding voltage need to be
constantly realigned.
Measuring and The parameters "welding current" and "welding voltage" are constantly measured. A
regulating the microcontroller continually compares the welding current that was pre-set on the setting
parameters dial with the actual welding current that is measured by the shunt. The transistors of the
"welding current" power-pack are addressed so as to raise or lower the welding voltage to the value that
and "welding is needed for keeping the pre-set welding current constant.
voltage"
Taking the rod-electrode welding process as an example, Fig. 10 shows the working
ranges of the power source as a function of the actual condition of the arc.
A complex regulation strategy is called for
At operating point (3), a decrease in the frequency corresponds to an increase in the output voltage
Also at operating point (4), a decrease in the frequency corresponds to an increase in the output voltage
By decreasing the frequency, then, the output voltage can be clearly brought back towards the value for operating
point (3)
T1
C
S
T2
C
P
Block diagram of theTP 1500 power-pack
The power transistors T1 and T4 apply the
voltage for the positive half-wave to the
T3
primary winding of the transformer. The
capacitor C
the coil L
S
resonance circuit here. The negative half-
L
S
T3
wave is switched to the series resonance
circuit by the power transistors T3 and T2.
P
S The secondary winding S of the
Inductor
transformer transmits the positive and
negative half-waves - as the welding
current - to the secondary diode D, which
actually consists of two separate diodes.
D
socket via one of the two end-taps of the secondary
P
21
, the primary winding P and
S
together constitute the series
is located parallel to the load
in response to an
P