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Maximized uptime and throughput from the EFD Induction Weldac

EFD Induction’s ‘Weldac’ induction welders have revolutionized uptime and productivity levels in the tube and pipe industry. Thanks in part to its patented switching technology, the Weldac is able to use reliable, standard IGBT transistors—even at the higher frequencies (now up to 500 kHz) needed for smaller dimensioned tube welding. The innovation means tube and pipe manufacturers can now get all the familiar advantages of MOSFET welders (high power efficiency, low operating costs) together with the unrivalled reliability and uptime of IGBT transistors. Indeed, the Weldac is so reliable that EFD Induction warrants the system’s IGBT inverter modules and driver cards for a total of five years of operation.

EFD Induction Weldac


Short circuit-proof

Comments Peter Runeborg, head of induction welding at EFD Induction: "IGBT transistors have been around for years. But their properties have limited their use to lower-frequency induction heat applications (typically up to 150 kHz), such as welding larger pipes. Small tubes usually require higher frequencies—an area dominated by MOSFET transistors, despite them being more costly and less reliable."


The secret behind the high-uptime Weldac is a patented internal switching pattern that boosts the frequency of IGBTs to as much as 500 kHz, making them ideal for welding smaller dimensions. A major advantage of the IGBT transistors is that they are virtually immune to coil short-circuits, caused, for example, by metal slivers getting caught between the coil and the tube or directly across the coil terminals. While this can destroy a MOSFET transistor, the IGBT-equipped Weldac is not affected.  


Easy operation and automatic matching

The Weldac underlines EFD Induction's focus on safe and easy operation. As Runeborg puts it: "The Weldac is a breeze to operate, with a minimum of manual settings and operator interventions. For example, coil changes take only seconds, with the frequency adjusting automatically to each tube dimension."


Weldacs up to 600 kW are housed in a single compact cabinet with a much smaller total footprint than their predecessors. No separate power or rectifier unit means there are no cables linking them to the welding station. Valuable space is saved. Installation is simplified. And because the single-cabinet design costs less to make, the Weldac series costs less to buy.          


The Weldac also offers continuous electronic load matching over a wide range of tube sizes, ensuring maximum performance during welding and when changing tube sizes. The matching is performed electronically within the inverter modules. There are no mechanically moving parts that are prone to wear, and no need for operator intervention.    


Lower costs and energy consumption

According to Runeborg, many customers have already replaced their obsolete vacuum-tube technology with Weldacs. "Well, the commercial benefits of switching to a Weldac are compelling. Vacuum tubes are increasingly expensive as the worldwide supply dries up. Besides, they are energy-inefficient and short-lived. Vacuum-tube systems require higher maintenance and are more costly to use."          


For a standard Weldac system, the total efficiency from input terminal to the terminal on the busbar is around 85% or better. Other cost-cutting benefits come from the Weldac’s use of a diode rectifier, which ensures the Cos φ parameter is a constant 0.95 for all power levels. This means tube and pipe manufacturers do not have to pay for reactive power or for compensation capacitors.          


The use of a diode rectifier also means the output power is regulated in the inverter module. This results in very fast regulation and recovery following a short circuit in the load. The response time for a Weldac system is related to the operating frequency of the inverter, not the mains frequency as is the case with controlled rectifiers (thyristors).      


Solid-state leader

The Weldac series confirms EFD Induction’s reputation as the leader in solid-state induction technology. "Everyone in the business knows we've been at the forefront of this technology since the early 1980s,” says Runeborg. “In fact, we developed and commercialized some of the world's first transistorized systems. Our Weldac welders, also known as ELVA welders, became a big hit. By using more rugged and less costly standard transistor components—which until now have been unsuited for high-frequency tube welding—we've created a whole new level of reliability and cost efficiency for tube and pipe manufacturers.”    


Key benefits:

  • Patented IGBT design gives high uptime and production output, five years warranty on inverter modules
  • Short circuit-proof , safe and reliable operation
  • Wide electronic automatic matching range and automatic frequency adaptation, no operator intervention required
  • No unsafe or restricted operating areas within the total matching range, no stop outside the “full power matching range”
  • Diode rectifier gives high-power factor at all power levels, reducing costs and minimizing reactive power from the mains supply
  • Compact design, all-in-one single cabinet up to 600 kW
  • Small footprint, fast installation, easy to retrofit
  • Divided control system, can be incorporated into any line control system
  • Low cooling water consumption due to high efficiency Dual welders, both induction and contact welder in one unit  


Weldac features:

  • Can be delivered with different output power levels: 50-2000kW and a frequency range of 60-500 kHz
  • Modular inverter design
  • 100% equal current sharing between inverter modules
  • No high current or over-voltages occur during coil short-circuits
  • On-site power upgrade is available
  • Frequency switching is available
  • Tube range OD ¼”-26” or larger, and various profiles, wt 0.2-25.4mm
  • Solutions with single turn, two and three turn coils and contacts
  • Materials: Carbon steel, magnetic and non-magnetic stainless steel, galvanized, aluminum, copper and brass
  • Prepared for 12-pulse rectifier for even lower harmonic distortion on mains supply above 1200 kW
  • Extra filter for even lower harmonic current distortion on mains supply is available as an option for power levels below 1200 kW
  • Low loss Intermediate Matching Transformer (only transfer of active power) gives safe galvanic isolation between load and mains supply
  • Minimized internal inductance design minimizes voltage level
  • Well-proven, high power, low voltage output capacitors  


To learn more about the technical and business benefits of the Weldac, contact Peter Runeborg.

Office phone:        +47 35 50 60 89

Mobile phone:       +47 90 97 47 55

Fax:                      +47 35 50 60 10

E-mail:                  pru@efdgroup.net