Technical Bulletin

Induction heating makes shrink-fit connections simple to assemble and disassemble by uniformly and gently heating and expanding the outer component of the assembly without overheating any one area. Since an induction generator’s output power can be controlled via a thermocouple or pyrometer, the generator can control the process to regulate and limit the component temperature automatically. This control ensures that an established set-point temperature is not exceeded.

In figure 1 of our example, a motor housing is uniformly heated in order to expand for assembly without negatively affecting the microstructure. In this case, the induction coil is an ID heating coil that is placed inside the housing.The thermal image in figure 2 shows a typical heat distribution pattern in a motor housing heating application.

thermal-image.pngFigure 3 shows another rotor ready to be heated by a scanning induction coil. In this instance, the coil is designed to heat both the ID and the OD of the rotor at the same time. By allowing the coil to scan along the length of the rotor, the same coil and tooling setup can be used for rotors of Shaft Shrink Fitting.pngmultiple lengths, provided they all have the same inner and outer diameters.

In the case of small to mid-size electric motors, eldec recommends using ECO LINE medium-frequency generators (MFG) and custom manufactured inductors. eldec's medium-frequency generators (both ECO and CUSTOM LINES) have a wide variety of configuration options that can be matched to specific applications for electric motors and generators including (but not limited to):



  • Joining electric motor housings
  • Joining motor shafts and rotors
  • Short circuit ring brazing
  • Other brazing applications

These powerful and robust induction generators are available in the ECO LINE with power ratings ranging from 5 to 150 kW and frequencies from 8 to 40 kHz. eldec CUSTOM LINE medium frequency generators are built with power ratings up to 500 kW and larger for large industrial electric motors. All MFG ECO LINE Generators may be built standard with a Power Boost feature that allows you to over-dive the 100% continuous duty rating by an additional 50% for up to eight (8) minutes. Strengths include igbt transistor technology, precise energy dosing and an efficiency rating of over 90 percent.

Virtually maintenance free, ECO LINE medium-frequency generators operate quietly, take up little space and can easily be integrated into a cell controller thanks to a standard high speed PLC and multiple control options. In addition, the generators are available with single output or multiple output transformers. These connection options allow energy to be delivered sequentially (one side at a time), simultaneously (power provided in parallel and individually controlled), or symmetrically (power provided in parallel and working together, not individually controllable).

At eldec every project, including process analysis, begins with a consultation with our knowledgeable application engineers. Contact us and learn how eldec can assist you.