Posted in | Process Control

Simultaneous Heating with Medium and High Frequencies with SDF Generators

The CUSTOM LINE SDF® (simultaneous dual frequency) generators from eldec feature a high power density in simultaneous dual frequency technology. Two different frequencies act simultaneously on the workpiece to be heated, resulting in the entire component to be induction-hardened with totally uniform temperature and depth.

New precision – maximum flexibility

The exceptional benefits of this patented technique are particularly clear when hardening complex parts. Take gearwheels as an example: While medium frequencies effectively penetrate more deeply into the gearwheel, primarily heating the tooth base, the high frequencies heat the tooth tip. This is why the SDF® technique applies two different frequencies concurrently to the workpiece to be heated. The entire component is heated with completely uniform depth and temperature.

The SDF® generators have one MF converter and one HF converter sharing a common power output, with HF oscillation being superimposed on the standard medium-frequency oscillation during the SDF process.

However, the conventional application of HF and MF energy is always possible as well, providing the user with a versatile generator with high power density - Power: 50 – 3,000 kW; Frequency: 10 kHz to 25 kHz and 150 kHz to 350 kHz

The eldec SDF® generators are primarily used in complete hardening systems. The eldec SDF® generators are provided with an electrical cabinet.


The main advantages of the CUSTOM LINE SDF® generators are as follows:

  • Little to no surface oxidation
  • Versatile use as pure HF or MF generator
  • Can be integrated into automated lines
  • Low energy consumption per workpiece
  • Minimization of component warpage
  • Simultaneous heating with medium and high frequencies
  • Accurate surface hardening on complex contours
  • Combination of pulse width modulation and pulse train control
  • High-speed PLC with eldec control print: short clock frequencies for very quick control
  • Unique and globally patented – simultaneous heating with medium and high frequency
  • Especially beneficial for the contour-true edge layer hardening of complex surface geometries
  • Device protection by robust IGBT transistor technology: Short-circuit and open circuit proof. Even accidental workpiece contact does not damage the generator.
  • High efficiency of more than 90% in all power classes
  • Precision energy dosing for high reproducibility and therefore superior process capability (SPC)
  • Microprocessor-controlled high-speed eldec control print and PLC for control cycles in single-figure milliseconds
  • Maximum energy density => short process times

SDF® power 50 – 3,000 kW

Type / Rated
Power connection
+ 10% 50/60 Hz
Required cooling water
without inductor
Generator dimensions /
transformer dim.
  V A l/min W x H x D mm kg W x H x D mm
SDF® 50 3 x 400 100 80 1000 x 2100 x 600 280 125 x 480
SDF® 75 3 x 400 250 100 1000 x 2100 x 600 300 370 x 350 x 500
SDF® 100 3 x 400 200 100 1000 x 2100 x 600 320 370 x 350 x 500
SDF® 150 3 x 400 300 150 1000 x 2100 x 600 350 370 x 350 x 500
SDF® 200 3 x 400 400 160 1100 x 1980 x 600 500 370 x 350 x 500
SDF® 300 3 x 400 600 180 1100 x 1980 x 600 700 370 x 350 x 500
SDF® 450 3 x 400 1000 200 2000 x 2000 x 1200 800 350 x 350 x 650
SDF® 800 3 x 400 1600 250 2000 x 2000 x 1200 1200 350 x 350 x 650
SDF® 1000 3 x 400 2000 350 2000 x 2000 x 1200 1500 350 x 350 x 650
SDF® 3000 3 x 400 6000 500 6000 x 2000 x 1200 3000 350 x 350 x 650


SDF® Options

  • Profinet
  • Profibus interface
  • Energy controller
  • Ground fault monitor
  • Current and voltage display
  • Coolant systems to order
  • Temperature control with pyrometer

SDF® Generator Controller

Process monitoring is very important for induction hardening, and due to this EMAG eldec induction GmbH has designed an RFID interface between the inductor and machine. The geometry and properties of the inductors used are vital parameters which must be monitored during hardening processes.

An RFID system fundamentally comprises of a writeable chip and a read-write unit. The read-write head is integrated in the inductor support while the chip is fitted in the inductor foot.

A variety of data, such as the equipment code, number of heating cycles, possible positioning instructions for the machine, information about repairs/modifications made, and flow values can be saved. The interaction between the RFID system and the hardening machine ensures the precise identification of the exact tool for the component and full documentation of the history and properties of the inductor.

SDF® Coolant System

eldec Coolant Systems

The eldec generators are typically watercooled due to their high power density. All eldec’s generators and systems are supplied with ideal active or passive coolant systems to order.

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