Induction Heating for Shrink-Fit Connections

Induction heating makes shrink-fit connections easy to assemble and disassemble by evenly and gently heating and expanding the outer part of the assembly without overheating any specific area. Since an induction generator’s output power can be regulated via a pyrometer or thermocouple, the generator can control the process to adjust and limit the component temperature automatically. This control guarantees that a pre-determined set-point temperature is not exceeded.

In Figure 1 of eldec’s example, a motor housing is evenly heated so as to expand for assembly without negatively impacting the microstructure. Here, the induction coil is an ID heating coil that is positioned inside the housing. The thermal image in Figure 2 reveals a common heat distribution pattern in a motor housing heating application.

Induction Heating

Figure 1

Generators for Induction Heaters

Figure 2

Figure 3 illustrates another rotor ready to be heated by a scanning induction coil. In this example, the coil is built to heat both the ID and the OD of the rotor simultaneously. By allowing the coil to scan along the length of the rotor, the same coil and tooling arrangement can be used for rotors of various lengths, given that they all have the same outer and inner diameters.

Generator for Induction Heaters

Figure 3

Small to Mid-Size Electric Motors

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

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

These robust and powerful 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 designed 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 users to over-dive the 100% continuous duty rating by an extra 50% for up to eight minutes. Strengths include precise energy dosing, igbt transistor technology and an efficiency rating of more than 90%.


Virtually maintenance free, ECO LINE medium-frequency generators work quietly, occupy little space and can easily be incorporated into a cell controller owing to a standard high speed PLC and a range of control options. Furthermore, the generators are available with single output or multiple output transformers. These connection options allow energy to be supplied 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, all projects, including process analysis, begins with a consultation with its knowledgeable Application Engineers.

Eldec LLC

This information has been sourced, reviewed and adapted from materials provided by Eldec LLC.

For more information on this source, please visit Eldec LLC.


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