The next generation PRO 300 diesel welding generator from Miller Electric Mfg. Co. features improved reliability through fewer and more robust electronic components. An optional 4-cylinder, 24-HP Deutz engine provides more power for using larger electrodes and gouging with carbons up to1/4-in. diameter. More power also compensates for less oxygen when working in higher elevations.

The improved PRO 300 also offers better E6010 performance for downhill pipe welding, as well as better MIG, flux cored and TIG arc starts. Designed for construction fleets, small contractors and pipe welding applications, the PRO 300 provides 20 to 410 amps of welding power, as well as 12,000 watts of peak generator power.

"Deutz engines, parts and service centers are widely available in the construction and rental markets," says Joe Gitter, product manager, Miller Electric. "The D2008L4 Deutz engine we selected offers superior reliability and smoother, quieter operation. It offers 9 percent more horsepower than our other engine option, which helps ensure full output when welding at high altitudes."

More Reliable
The new PRO 300 design features a single circuit board (the previous design used two circuit boards). The single board, which Miller also simplified for greater reliability, is housed in Miller's unique "Vault." Created out of two aluminum halves sealed with silicone, as well as a watertight harness for connections, the Vault provides a clean circuit board environment, protecting the electronics of the machine in heavy industrial applications. Without the sealed environment, circuit boards are exposed to harsh elements that can disrupt the electronics. Based on Vault-related warranty claims versus number of products sold, the PRO 300 shows a 98.4 percent reliability rating.

Arc Improvements
"We've worked really hard to satisfy the demands of downhill pipeline welders by improving E6010 Stick electrode performance," says Gitter. "Pipe welders will notice a more focused arc in the root and hot pass, and they'll notice that the dig control comes in a little earlier [at higher voltage]. This compensates for voltage drops caused by long cable lengths or potentially bad connections." The more focused and steady arc is especially noticeable when running smaller 1/8- and 3/32-in. diameter E6010 electrodes.

When Stick welding, the PRO 300 a four-position control, B, C, D positions that adjusts Stick arc force. Arc force is the amount of "dig" or "drive" created at the end of the electrode that pushes the molten metal into the joint. This produces a more uniform bead with good penetration, good tie-in and less chance of undercut. For pipe welding with an E6010 electrode, Miller recommends using position C or D (positions A and B are generally used with E7018 electrodes).

To improve already excellent MIG/FCAW performance, Miller added digital voltage control (DVC), which enables operators to pre-set and maintain voltage (this is a standard feature on most industrial MIG welders). DVC creates more stable arc starts and eliminates the "pop" at arc start that also creates spatter. It also helps when running T-8 self-shielded flux cored wires, as they operate in very narrow voltage range compared to other wire types.

The PRO 300 also features better TIG arc starts and stops. An enhanced Lift-Arc function creates more consistent and positive arc starts, eliminating arc flutter or wander. At the end of a weld, a new Auto-Stop function allows the welder to break the arc without flaring it yet hold the torch close enough to the work to maintain good shielding gas coverage.

Other Improvements
The PRO 300 now features a low fuel shutdown function that shuts down the engine before fuel runs out. This eliminates a potentially long re-priming process when restarting the engine. A new maintenance alert meter indicates the number of hours between oil change intervals, helping operators adhere to a routine maintenance schedule. The meter also indicates a high temperature or low oil pressure condition.