Cebora 965, Service Manual, Page: 4 / 24

CEBORA S.p.A.
4
2 - SYSTEM DESCRIPTION
2.1 - Introduction.
The PLASMA PROF 55 is a system for cutting electrically conductive materials, using a
plasma arc process.
It is made up of an electronic power source (art. 965), with built-in torch.
The power source is controlled by microprocessor circuits, which manage the operative
functions of the cutting system and 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. 965.
Art. 965 is a direct current power source, essentially consisting of a three-phase transformer
and a rectifier bridge.
Referring to the electrical diagram in par. 5.1, the drawing in par. 4.1 and table 4.2, we can
identify the main blocks that make up the power source.
The switch (29) powers the power transformer (44), the primary circuit of which consists of
three windings that, star-delta appropriately switched by the switch (29), allow the power source
to operate at 230 or 400 Vac (for mains voltage selection see Instruction Manual).
Voltage may be delivered (always at 230 Vac) from 2 terminals of one of the primary winding
of the transformer (44), to power the lamp (38) (mains voltage presence), the control board (6)
and thus auxiliary services (fan, contactor, solenoid valves).
The power transformer (44) secondary winding is connected to the contactor TLP (30), that
when closed, supply the three-phase rectifier bridge (32) that rectifies the power source output
voltage.
At the rectifier bridge (32) positive output is connected the solenoid (43) with reed bulb (42)
to detect the cutting current on the earth conductor of the power source, and pilot arc resistors
(37), used for limiting pilot arc current and to facilitate the transferred arc operation.
At the rectifier bridge (32) negative output is connected the HF transformer (31) used to
engage the pilot arc.
The control board (6) manages the power source output voltage, by means of the input
contactor TLP (30) and the firing of the pilot arc, by means the built in HF generator circuit.
Combined with the HF transformer (31), generates the high voltage and high frequency pulses
needed to start the pilot arc. Its operation is controlled by the microprocessor on control board
(6) and is subject to the rectifier bridge (32) output voltage presence.
Near the output terminals of the power source is the HF-filter board (47), which serves to
prevent the high voltage and high frequency pulses generated by the HF transformer (31) from
traveling along the wiring into the power source, where they would cause malfunctions or errors.
Therefore, during maintenance operations, make sure that this board is always firmly connected
to the original terminals before striking the arc.
The pressure switch (33) inserted on the plasma gas line stops the power source and lights the
lamp (L)(45) when the pressure falls below the minimum permitted value.
The thermostat in reality is made by two thermostatic switches connected in series between
them, located on two columns of the transformer (44) (temperature correct = contacts closed).
The intervention of one of the two thermostats is sufficient to produce the power source block,
signaled by lamp G (45).
With the switch (29) closed, the control board (6) is powered and awaiting for the start signal
from the torch button. The power source provides no output voltage.
3.302.173 28/07/04