Functional Description; Functional Principle - Bosch PSU 5000 Series Instructions For Assembly And Operation Manual

Functional description

3

3.1 Functional principle

1070 078 224--- 108
PSU 5000 / PSG 3000
Instructions for Assembly and Operation
The figure below shows the difference between welding equipment with
1---phase AC and medium---frequency DC.
50 / 60 Hz
50 / 60 Hz
Timer
1 / 1.2 kHz
50 / 60 Hz
Timer
The medium--frequency welding system (MF welding system) is used for resis-
tance welding with direct current; it consists of the inverter (PSU) and the trans-
former--rectifier (PSG).
For selection of the welding parameters, the inverter is controlled by a weld timer
with a 5 kHz weld output cycle. As an option, it may also be controlled by a 24 V weld
time signal and an analog input voltage (1--10V) (for both control options see Sec-
tion 8, "Controlling the inverter").
The 3--phase 50 / 60 HZ mains AC is first rectified by a bridge connected rectifier
(B6 connection). The direct current thus generated connects a transistorized H--
bridge alternatingly to the welding transformer with a frequency of 1 / 1.2 kHz. The
welding current is rectified at the secondary side of the welding transformer.
The amount of the welding current is determined by control of the pulse width. The
welding current is measured by a toroid measuring coil incorporated in the secon-
dary circuit of the welding transformer.
In contrast to single--phase AC systems, the inverter controls the welding current
independently.
1- -phase alternating current
Thyristor
Welding
power stage
transformer
Medium- -frequency direct current
3~
MF inverter Transformer--
rectifier
Functional
description
Welding
apparatus
+
--
Welding
apparatus
3--1