Testing Ac Output Units For Correct Phasing Prior To Parallel Operation - Miller DC1000 Owner's Manual

3-9. Testing AC Output Units For Correct Phasing Prior to Parallel Operation

To Separate Electrode
(Electrically Isolated From
All Other Electrodes)
First (Master) Unit
Connections
Y If there are any questions regarding this procedure,
contact the factory before connecting units.
To Work
Second (Slave) Unit
(And Following Units)
Connections
Shielded Cable To
Terminal Strip TE4
(See Section 3-6)
Set on AC Volts Scale
Meter Polarity Does Not Matter
To Separate Electrode
(Electrically Isolated From
All Other Electrodes)
To Next AC Unit
To Work
Y Turn Off welding power
sources and disconnect in-
put power before opening
access door.
Y If units are not phased cor-
rectly, the welding power
sources may be damaged.
Y Open-circuit voltage will be
present on all electrodes
during this check. If the ma-
chines are not phased cor-
rectly, the voltage between
electrodes may equal two
times open-circuit voltage
(135 - 145 volts ac). Have only
qualified persons do this
testing.
Be sure synchronizing connections
in Section 3-6 have been made be-
fore performing this procedure.
Make connections as shown in il-
lustration. Connect ac voltmeter
between electrode connected to
first (master) unit and electrode
connected to second (slave) unit.
Power On both units and place both
output control switches in On posi-
tion. When the units are properly
phased, the voltmeter will read
less than one volt ac.
If the meter reads more than one
volt ac, the unit's primary lines are
not matched in the proper phase
sequence (see Section 2-16).
After performing the test in Section
2-16, retest the units for phasing.
When the second (slave) unit is in
phase with the first (master) unit,
test phasing between third unit (if
applicable) and second unit. Al-
ways test and correct phasing be-
tween following unit and the unit
previous to it (check fourth unit
against third unit, fifth unit against
fourth unit, etc.).
After setting units up for correct
synchronizing, connect units ac-
cording to section covering desired
multiple unit use (see Sections 3-2,
3-3, and 3-5).
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