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diameter that can be used to weld with a sharp<br />
tip based on the current and balance being used.<br />
Frequency control<br />
The arc cone can be further narrowed by increasing the<br />
AC frequency. On conventional machines, frequency<br />
was limited to 60 Hz. The frequency adjustment range<br />
on the MasterTig MLS 2300 ACDC power source is<br />
50-250 Hz. However, the factory-preset is 60 Hz, because<br />
increasing the frequency considerably increases<br />
the noise level. For example, when welding at 100 A the<br />
noise level rises from 82 dB(A) to 91dB(A), when the<br />
frequency is increased from 60 Hz to 250 Hz.<br />
The frequency should be increased if there are diffi culties<br />
focusing the arc. This often occurs when welding at<br />
low frequencies.<br />
Waveform control<br />
The MasterTig MLS 2300 ACDC power source offers<br />
two waveforms: squarewave and sine wave. Both are,<br />
however, modifi ed slightly from the theoretical wave-<br />
”<br />
A rule of thumb is that<br />
form. The squarewave has rounded corners because<br />
it dampens the noise level considerably. On the other<br />
hand, when using the sine wave the zero-line is crossed<br />
at maximum speed, thus making half-wave ignition as<br />
good as when using a squarewave. Because a squarewave<br />
can be aimed more effectively than a sine wave, it<br />
is installed in the machine as a factory-preset. The drawback<br />
with the squarewave is the 2-4 dB(A) higher noise<br />
level, i.e. if the noise is too loud, the user can switch to<br />
sine wave. n<br />
28<br />
one should use as much<br />
EN in the ratio as possible<br />
when welding.<br />
<strong>Kemppi</strong> ProNews 2 • 2006<br />
Questions & Answers<br />
I hava a Minarc 150 MMA welding machine, which I generally use to do all<br />
sorts of repair work. Right now I’m fi xing a mount fi tting on the pier at my<br />
summer cottage which was broken by pack ice. There are no power outlets<br />
at the shoreline – the closest outlet is 30 metres away at the sauna. What<br />
can I do? Taking the pier apart and moving it to the sauna isn’t a very appealing<br />
idea.<br />
The Minarc 150 will work perfectly with a 50 metre extension cord. Just make<br />
sure that the cord is of high quality and its diameter is at least the same as<br />
used on the welding machine itself. Indeed, the Minarc 150 will also work<br />
with a generator set. The power output of the generator set must be at least<br />
6 kVa.<br />
How is it possible that I can weld with my machine even though the negative<br />
cable isn’t connected?<br />
Most likely the workpiece and structural ground (the frame of your welding<br />
machine) are in contact with one another, and the welding current is traveling<br />
along the welding machine’s grounding cable. In this case the risk of damage<br />
to the grounding cable is extremely high. In order to ensure safe operation,<br />
it would be wise to take the machine to an authorized <strong>Kemppi</strong> service centre<br />
for a check-up. The problem can be avoided by isolating the workpiece and<br />
structural ground from one another.<br />
Is it cheaper to repair a welding machine at the <strong>Kemppi</strong> plant than it is at<br />
an authorised service centre?<br />
No. Actually, the <strong>Kemppi</strong> plant does not do any repair work on customer<br />
machines whatsoever. Repairs are only made at authorised <strong>Kemppi</strong> service<br />
centres.<br />
Our new FastMig Basic KM machine shows a maximum wire feed of 100<br />
m/min. Is such a high wire feed rate even possible? How can this fault be<br />
fi xed?<br />
This isn’t a fault. The FastMig Basic KM display doesn’t show the wire feed rate,<br />
but rather the percentual value of the maximum wire feed rate. The percentual<br />
reading has been chosen, because the FastMig Basic KM power source<br />
can be used with diff erent wire feed units, and the power source has in this<br />
case no way of reading the wire feed unit’s feed rate.<br />
For how long are spare parts for a <strong>Kemppi</strong> machine no longer in production<br />
available?<br />
Spare parts are available for 10 years.<br />
If a MIG welding machine has a current display, why does the readout fl uctuate<br />
tens of amperes while welding?<br />
A MIG welding machine is a constant current source, in which the voltage<br />
stays nearly constant while welding. Conversely, the power readout can vary<br />
tens of amperes depending on the stick-out length. The longer the free wire,<br />
the lower the current value, and vice versa.
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