Operating instructions

004 859 Page 12
3-5. Paralleling AC Constant Current Transformer-Type Power Sources
AC transformer-type power sources can be paralleled for increased amperage demands; however, additional precautions must be taken.
The following procedure is recommended:
1. Connect primary wiring of suitable size from each power source to the same phase in the main disconnect switch box. This arrangement enables
all power sources to be connected to the power lines simultaneously when the line disconnect switch is placed in the “On” position.
All primary connections should be made by a qualified electrician. Wire and fuse sizes must be in accordance with National Electrical Code specifi-
cations and local code requirements.
When connecting two or more power sources in parallel, the primary side of each power source must be individually protected (fused).
Primary wiring from the primary terminals to the common switch should be the same length and size. It is desirable that the junction of the primary
wiring be made at the line disconnect rather than at the power source terminal board.
2. Make sure all power sources connected in parallel have the proper phase relationship. Check this as follows:
a. Temporarily connect all electrode terminals together with a No. 14 AWG or larger wire.
b. Energize all power sources.
c. With a voltmeter, check the voltage across the work terminal of one power source and the work terminal of the other power source(s). If the
voltage is approximately zero, the phase relationship is correct. If, however, the voltage is substantially greater than zero and slightly less
than two times the individual machine open−circuit voltage, the phase relationship is incorrect. Reverse the primary connections on one
power source at a time until zero volts between all work terminals is achieved. Remove the temporary jumper wires connecting the electrode
terminals.
3. When making secondary cable connections, the same procedure and recommendations outlined for DC constant current transformer/rectifier
power sources should be used. Be sure connections are made work to work and electrode to electrode.
4. When using AC, power source control systems must be synchronized according to the instructions provided in the power source Owner’s Manual.
3-6. Paralleling AC/DC Constant Voltage/Constant Current Transformer/Rectifier Type
Power Sources
When connecting two or more units in parallel, do not use more than one unit in CV mode. If constant voltage output is required, operate only one unit in
the CV mode and put the remaining units in the CC mode with their output set to a percentage of total welding output divided by the total number of units
used. When using AC, be sure the input power phase relationship is correct according to Section 3-5 and that power sources control systems are
synchronized according to their instructions.