System Description; Introduction; Technical Specifications; Description Of Power Source Art. 961 - Cebora 961 Service Manual

CEBORA S.p.A.

2 - SYSTEM DESCRIPTION

2.1 - Introduction.

The PLASMA PROF 37 is a system for cutting electrically conductive materials using the
plasma arc process. It is made up of an electromechanical power source, art. 961, with built-in
torch, controlled by electronic circuit to manage the operative functions of the cutting system and
the operator interface.

2.2 - Technical specifications.

To verify the technical specifications, see the machine plate, Instruction Manual, and Sales
Catalogue.

2.3 - Description of power source art. 961.

Art. 961 is a direct current power source consisting of a three-phase transformer and a three-
phase rectifier bridge.
Referring to the electrical diagram in par. 5.1, and drawing 4.1 and table 4.2, we can identify
the main blocks that make up the power source.
The switch (40) powers the power transformer (38), the primary circuit of which consist of
three windings, that connected in star or delta connection by the switch (40), allow the power
source to operate at 230 or 400 Vac (for selection see Instruction Manual).
Voltage may be delivered (always at 230 Vac) from 2 terminals of one of the primary
windings of the transformer (38), to power the lamp (22) (mains voltage presence), the control
board (4) and thus auxiliary services (fan, contactors, solenoid valves).
The power transformer (38) secondary winding is connected to the contactor TLP (32), that
when closed, supply the three-phase rectifier bridge (33) that rectifies the power source output
voltage.
At the rectifier bridge (33) positive output is connected the pilot arc resistor (36), used for
limiting pilot arc current and to facilitate the transferred arc operation.
The control board (4) manages the power source output voltage, by means of the input
contactor TLP (32) and output contactor TLM (32), based on the signals present at its inputs.
With the switch (40) closed, the control board (4) is powered and awaiting the start signal
from the torch button. The power source provides no output voltage.
When the start button on the torch is pressed, the control board (4):
− opens the gas solenoid valve EL1 (7);
− after the pre-gas time (approximately 500 msec., non adjustable) opens the solenoid valve
ELT (6);
− after other 300 msec. closes input contactor TLP (32) and output contactor TLM (32).
The solenoid valve ELT (6), drives the pilot arc firing ram inside the torch, that, when under
pressure, push in shot-circuit electrode and nozzle of the torch. Since solenoid valve ELT (6)
remains opened only 400 msec., the momentary short-circuit between electrode and nozzle
interrupts at the end of such time, when between the two terminals is present the power source
output voltage, so that, inside the torch plasma chamber, strike the arc, due to short-circuit
interruption with voltage applied, to light the pilot arc.
Obviously, with this system, we have only one tentative to light the pilot arc every time you
press the torch start button.
If pilot arc doesn't start, control board (4), detecting a power source output voltage greater
than 200 Vdc, set the power source at its resting state, with TLP (32) and TLM (32) opened. This
system performs a safety function against electrical shock from contact. It eliminates the risk of
electroshock that the operator would face by touching the ground contact and the torch, in the
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