Cebora PLASMA PROF 123 ACC Service Manual page 5

CEBORA S.p.A.
The J1 terminal of the power board (56) corresponds to the positive output (3) of the igbt
module as well and represents the nozzle potential output. The nozzle resistor (33) which
facilitates the operation with the pilot arc is connected to it. On this connection as well, inside the
power board (56), the Hall effect current transducer is connected which sends to the control
board (47) the pilot arc current signal.
The system current is adjusted by the control board (47).
It generates the igbt drive signal, obtaining the waveform (duty cycle), based on a comparison
between the current reference signal originating from the control board (47) and the current feed-
back signal originating from the current transducers on the power board (56).
The signals of the two current transducers are used also for switching the pilot arc and the
transfer arc.
More precisely:
- when the Power Source output current (transducer signal on TP1) is the same as the pilot arc
current (transducer signal on J1) the control drives the pilot arc operation, with the nozzle
contactor (55) closing.
- when the Power Source output current (transducer signal on TP1) becomes higher than the
pilot arc current (transducer signal on J1) the control drives the transfer arc operation (cutting)
and opens the nozzle contactor (55).
The fuse board (53) contains the fuses related to the electronic boards and Power Source
internal services (contactors and solenoid valves) power supply.
The supply board (51), powered by the fuse board (53), generates the control board (47)
power voltage. On the input voltage of the supply board (51) a control circuit is provided, which
generates an error signal if this voltage becomes 30% lower than the rated value. This error
signal is sent to the control board (47) and causes the immediate stop of the Power Source and
the code error is displayed on the operator panel (error 99 "OFF").
The pre-charge board (3) controlled by the control board (47) commands the power
transformer (37) pre-magnetization, through resistors R16, R17, R18 and relay RL3, fitted on the
pre-charge board (3).
The control board (47) contains the main microprocessor of the Power Source and manages:
− the other boards that are more specialized in the relative functions;
− processes the driver signal to be sent to the driver board (56) built in the power board (56)
igbt module;
− commands the line contactor (2) and the nozzle contactor (55);
− manages the plasma gas control devices (solenoid valves and pressure detector);
− manages the diagnostics of the cutting system, conditioning or stopping it as required, the
system operation and displays any code errors on the operator panel.
The control board (47) also manages the operator interface which, in this case, is the operator
panel built in the same board.
It contains:
- two displays (U) and (V) to show the type of connected cutting torch, error codes, cutting
current and nozzle hole diameter;
- a knob (Z) to set the cutting current;
- a series of leds to display the operating status;
- a button (W) for functions selection.
On the control board (47), inside the Power Source, the RS232 communication port (BD1) is
fitted, for connection to a Personal Computer, allowing the Power Source Firmware updating.
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12/04/2012