Welding Power Source Duty Cycle And Overheating; Volt-Ampere Curves - Miller Millermatic 251 Owner's Manual

4-2. Welding Power Source Duty Cycle And Overheating

500
450
400
350
300
250
200
150
100
50
10
60% Duty Cycle At 200 Amperes
6 Minutes Welding
Overheating

4-3. Volt-Ampere Curves

35
30
25
20
15
10
5
0
0 100
OM-1326 Page 10
20 30 40
% DUTY CYCLE
4 Minutes Resting
0
15
Minutes
200 300
AMPERES
Duty Cycle is percentage of 10
minutes that unit can weld at rated
load without overheating.
If unit overheats, Thermistor (T)
opens, output stops, and cooling
fan runs. Wait fifteen minutes for
unit to cool. Reduce amperage or
voltage, or duty cycle before
welding.
Y Exceeding duty cycle can
50 60 70 80 90 100
40% Duty Cycle At 250 Amperes
4 Minutes Welding
A or V
OR
Reduce Duty Cycle
1
1
The volt-ampere curves show the
normal minimum and maximum
voltage and amperage output
capabilities of the welding power
source. Curves of other settings fall
between the curves shown.
400
damage unit and void
warranty.
6 Minutes Resting
duty1 4/95 − 150 215-A
Normal Volt-Ampere Curves
ssb1.1 10/91 − 196 844 / S-0700