2.3
Brief
Introduction
GRAND TIG 250 DC PULSE adopts the latest Pulse Width Modulation (PWM) technology and the
Insulated Gate Bipolar Transistor (IGBT) power modules. It uses switching frequencies in the 20KHz-50KHz
ranges so as to replace the traditional line-frequency transformer type welding machines. Thus,
machines are characterized with portability, small size, lightweight, low energy consumption and noise,
etc. The parameters of the machine on the front panel all can be adjusted continuously and steplessly,
such as start current, crater arc current, welding current, base current, duty ratio, upslope time,
downslope time, pre-gas, post-gas, pulse frequency, hot start, arc force and arc length etc. When
welding, it takes high frequency and high voltage for arc igniting to ensure the success ratio of igniting
arc.
GRAND TIG 250 DC PULSE Characteristics
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DC Pulsed TIG and MMA, adopt IGBT and advanced PWM technology
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High performance MCU, Digital control, Digital display
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HF/Lift TIG, current down slope and up slope, gas post-flow, Pulse Frequency
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Intelligent protection: over-voltage, under-voltage, over-current, over-heat
1. For MMA, polarity connection can be chosen according to different electrodes;
2. For DC TIG, DCEP is used normally (workpiece connected to positive polarity, while torch connected
to negative polarity). This connection has many characters, such as stable welding arc, low tungsten
pole loss, more welding current, narrow and deep weld;
3. DC Pulsed TIG has the following characters: 1) Pulse heating. Metal in Molten pool has short time on
high temperature status and freezes quickly, which can reduce the possibility to produce hot crack of
the materials with thermal sensitivity. 2) The workpiece gets little heat. Arc energy is focused. Be suitable
for thin sheet and super thin sheet welding. 3) Exactly control heat input and the size of the molten pool.
The depth of penetration is even. Be suitable for welding by one side and forming by two sides and all
position welding for pipe. 4) High frequency arc can make metal for microlite fabric, eliminate blowhole
and improve the mechanical performance of the joint. 5) High frequency arc is suitable for high
welding speed to improve the productivity.
GRAND TIG 250 DC PULSE is suitable for all positions welding for various plates made of stainless steel,
carbon steel, alloyed steel, titanium, magnesium, cuprum, etc, which is also applied to pipe installment,
mould mend, petrochemical, architecture decoration, car repair, bicycle, handicraft and common
manufacture.
2.4
Duty cycle
and
Over-heat
The letter “X” stands for Duty Cycle, which is defined as the portion of the time a welding machine
can weld continuously with it’s rated output current within a certain time cycle (10 minutes). The
relation between the duty cycle “X” and the output welding current “I” is shown as the right figure. If
the welding machine is overheating, the IGBT over-heat protection sensing will send a signal to the
welding machine control unit to cut the output welding current OFF and light the over-heat pilot lamp
on the front panel. In that case, the machine should not be welding for 10-15 minutes to cool down
with the fanrunning. When operating the machine again, the welding output current or the duty cycle
should be reduced.
Relation of welding current and
duty
cycle for
GRAND
TIG 250 DC PULSE
