[Wobulate]

I was surfing the You Tube sight when I ran into videos of a Lincoln PT-225 20% duty cycle test at 183 Amps. It appears the load used was disapating the heat into approx. 40 gallons of water. I looked up my duty cycle data matrix and indeed I expect the internal temperature sensor to shut off the power around 2 minutes (approx. 20% of a 10 min. test period).
Test #1:
[youtube]http://www.youtube.com/watch?v=nRB1DQ6z_xU[/youtube]
Test #2:
[youtube]http://www.youtube.com/watch?v=a35PE4GQetU[/youtube]

Summary of 2 Tests:

Lincoln Electric Presision Tig 225 20% duty cycle test -1
The welder was setup as follows:
Load: 0.161 Ohms
Voltage: 29.6 V
Current: 183.8 Amps
Power: 5,440 Watts
Time before welder thermal shutdown: 4 min., 40% duty cycle
Based on a 10 minute time frame.
Shutdown at 2 min. would be a 20% duty cycle.

Lincoln Electric Presision Tig 225 20% duty cycle test -2
The welder was setup as follows:
Load: 0.143 Ohms
Voltage: 26.3 V
Current: 183.9 Amps
Power: 4,836 Watts
Time before welder thermal shutdown: 3 min. 42 sec., 37% duty cycle
Based on a 10 minute time frame.
Shutdown at 2 min. would be a 20% duty cycle.

Comments?
Wob

[Otto Nobedder]

One obvious possibility for these results, is a safety margin in the advertised rating, so they deliver better than promised. A compressor tank advertised for 150 PSI has actually been proven at 225, or 1.5 times the advertised maximum working pressure, as one example.

Another possibility is a quality issue with the particular machine used in the test. A comparison of several identical machines would be interesting.

Steve S

[noddybrian]

What was the ambient temperature & humidity conditions of the tests - factory tests are usually in " worst case scenario " conditions the set was designed for - probably 90% RH @ 40degrees (centigrade - sorry don't know what the F equivalent is ) so real world test are normally better unless you live in a rain forest !

[cocobolo]

What was the ambient temperature & humidity conditions of the tests - factory tests are usually in " worst case scenario " conditions the set was designed for - probably 90% RH @ 40degrees (centigrade - sorry don't know what the F equivalent is ) so real world test are normally better unless you live in a rain forest !

Converting from ºC to ºF is fairly easy. Freezing is 32ºF or 0ºC. So to go from ºC to farenheit, you start at 32 and then multiply the 40ºC by 1.8, which would be 72º. Add 32 to that and you come up with 104ºF.