Cebora KINGSTAR 400TS Manual De Servicio página 62

CEBORA S.p.A.
- the IGBT inverter, which generates square wave alternating voltage for power
transformer (53);
- AT (T1 for Item No 372 and T3 for item No 374) for detecting the current in the
primary winding of power transformer (53).
Power board (48) communicates with microswitch board (37) by means of signals
isolated using relays or pulse transformers.
Mains filter (39) contains:
filter for reducing reflected conductive interference on the mains network;
inverter DC capacitor precharging circuit;
check on presence of all three mains voltage phases
circuits for managing fans (21) and cooling unit (optional).
More precisely, it checks the presence of each single mains voltage phase and
generates the "MAINS" signal (mains power presence) to send to the microswitch board
(37). Depending on the signal, consent will be given for the power source to either run
or stop, with the corresponding error code displayed on the control panel (70). Mains
filter board (39) supplies the mains voltage for powering service transformer (38) which,
in turn, supplies power source boards (42/72) that generate the various service voltages
for system circuits.
The inverter consists of one module for Item No 372 and two modules for item No
374 (each module contains four IGBTs connected in an H-bridge configuration, driven
by driver circuits mounted on the power board (48) near the IGBT modules, controlled in
turn by the microswitch board (37).
The purpose of the IGBT inverter is to generate a square wave alternating voltage for
power transformer (53). The welding current is adjusted by modulating this voltage
accordingly.
AT T1 inserted in the circuit between the IGBT module and transformer (53) provides
microswitch board (37) with the current reaction signal of primary winding of transformer
(53), used to check that the inverter is operating correctly; this signal does not usually
affect welding current regulation.
Transformer (53) provides the secondary winding with appropriate welding voltage
and current values.
The secondary consists of four windings connected to a central socket. Inductance
(52) is connected to this socket in order to level the welding current.
The other ends of the secondary windings are connected to diode assembly (27),
which rectifies the alternating current generated by the inverter making it available at the
power source output.
Diode assembly (27) is made up of 4 diodes (Item No 372) and 6 diodes (Item No
374) connected with a common cathode. The output voltage is positive in relation to the
central socket of transformer (53). Each of these diodes is enclosed in modules by two
diodes.
The Hall effect current transducer (25), inserted at the output of diode assembly (27),
sends the microswitch board (37) the reaction signal of the secondary winding current,
used to adjust the welding current.
On the heatsink of the IGBT module on the primary winding and on the heatsink of
the diode assembly on the secondary winding, an NTC sensor sends a signal to
microswitch board (37) that is proportional to heatsink temperature.
Fans (21), used to cool the power source power elements, are controlled by the
microswitch board (37). This command passes through board (39). Its start and stop
operation depends on operational and environmental conditions:
3301045
62
17/09/2019