MK Welding PC 100 LCD CNC, Руководство пользователя

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12
EN
§2.3 Working Principle
The working principle of CUT series of Air Plasma Cutting machines is shown as the
following figure. Three-phase 380V line frequency (50/60 Hz) AC is rectified into DC, then it
is converted to medium frequency AC (about 20KHz) by inverter device (discrete IGBT),
after reducing voltage by medium transformer (the main transformer) and rectified by
medium frequency rectifier (fast recovery diode), and is outputted by inductance filtering.
The circuit adopts current feedback control technology to insure current output stably.
Meanwhile, the cutting current parameter can be adjusted continuously and steplessly to
meet with the requirements of cutting craft.
§2.4 Duty cycle and Over-heat
The letter “X” stands for Duty Cycle, which is defined as the portion of the time a air plasma
cutting machine can cut continuously with it’s rated output current within a certain time cycle
(10 minutes).
The relation between the duty cycle “X”
and the output cutting current “I” is shown
as the right figure.
If the plasma cutter is overheating, the
IGBT over-heat protection sensing will send
a signal to the plasma cutter control unit to
cut the output cutting current OFF and light
the over-heat pilot lamp on the front panel.
In that case, the machine should not be
cutting for 10-15 minutes to cool down with
the fan running. When operating the
machine again, the cutting output current or the duty cycle should be reduced.
Rectify Inverter
Medium
frequency
transformer
Medium
frequency
rectify
Hall device
Current positive-
feedback control
Three-phase, AC
DC
AC DC
380V
，
50Hz
AC DC
Relation of cutting current
and
duty cycle for PC 120