Technical information

Setup
2-4
1070 080 059-101 (2001.04) GB
2.3 Function
The medium-frequency welding system (MF welding system) is designed for
direct current resistance welding. Its key components are the PSI 6000 me-
dium-frequency inverter and the PSG 3000 MF welding transformer.
The figure below shows the basic functional design of the MF welding pro-
cess.
+
−
Weld timer
3~
Electrodes
Timer MF inverter Transformer-
rectifier
Basic functional design of the 1 kHz MF welding process
The 50 / 60 Hz mains AC is first rectified by a bridge connected rectifier
(B6 connection). The direct current generated connects a transistorized H-
bridge alternatingly to the PSG 3000 welding transformer at a frequency of
1 kHz. In secondary circuit, the transformer rectifies the welding current.
The intensity of the welding current can be controlled by adjusting the pulse
width. The welding current is measured either with a current sensor inte-
grated in the secondary circuit of the PSG 3000 welding transformer or, in the
case of a welding transformer without a current sensor, with a primary cur-
rent ammeter integrated in the MF inverter.
t
t
f = 1 kHz
[2] [1]
Primary voltage
I
SEC
Secondary current
[1] low current
[2]
high current
I
mean value
Primary voltage
setting range
U
PRIM
Primary and secondary voltages for medium-frequency welding
The welding current output of the welding transformer or, resp., the primary
current multiplied by the transformation ratio are measured and processed
in the welding control for monitoring and control purposes.