Specification and Use of a Flux Concentrator
Download as PPTX, PDF3 likes4,038 views
The document presents an overview of magnetic flux control and its applications in induction heating, focusing on the role of magnetic flux controllers, such as Fluxtrol materials, in optimizing the heating process. It details the benefits of using these controllers, including improved heat pattern control, energy savings, and enhanced part quality, emphasizing their importance in coil design. Examples and performance comparisons illustrate the advantages of various coil styles when utilizing magnetic flux concentrators.
Specification and Use of a Flux Concentrator
- 1. Mr. Robert Ruffini President Specification and Use of a Flux Concentrator 1 Customer Training Seminar, Shanghai, China, April 2014
- 2. Overview • Basics of Magnetic Flux Control • Effect of Flux Controllers on Different Coil Styles • Materials for Magnetic Flux Control • Influence of Magnetic Permeability • Selecting the Proper Flux Concentrator • Example: – Crankshaft Hardening Inductors • Conclusion 2
- 3. What is Magnetic Flux Control? • Magnetic flux control is a generic term for modification of induction coil magnetic flux by means of installation of magnetic templates (magnetic flux controllers) • Magnetic controllers may significantly change magnetic field pattern and coil parameters; their application must be considered as a part of the whole induction system design • Because Controllers play different roles (magnetic flux concentration, shielding, distribution) they are called also Concentrators, Cores or Shields depending on application • In many cases controllers fulfill several functions simultaneously 3
- 4. Magnetic Flux Controller Effects Effects: 1.Reduction of external field 2.Higher power in the part at the same coil current 3.Power concentration under the coil face 4.But… the coil current is concentrated on one side of the coil tubing resulting in higher losses Analysis can predict all the results. Power distribution on the part surface for same coil current Current Density on Part Surface 0 25 50 75 100 125 150 Postion on Part CurrentDensity Bare Coil Coil with Fluxtrol A No concentrator With concentrator 4
- 5. • Precise heat pattern control – Reduced Distortion – Improved Part Quality • Energy savings • Production rate increase • Longer Power Supply, Transformer, Capacitor and Bussbar Lifetime – Due to reduced current and kVAR. Improvement in power factor (cosØ) has a large impact on the losses in these components • Shielding of part or machine components from unintended heating 5 Possible Improvements due to Magnetic Flux Controllers
- 6. Effects of Magnetic Flux Controllers on O.D. Coils • Φ (phi) – Magnetic Flux causing heating • IN – Ampere turns of the coil (driving force of magnetic flux) • Zm – Magnetic resistance (Reluctance) of the “active zone” • Rm – Magnetic resistance for magnetic flux on return path • B – Magnetic Flux Density (Induction). It describes magnetic loading of controller material. 6 Φ = IN / (Zm + Rm) Applying controller we reduce Rm and therefore increase magnetic flux with the same coil current or reduce current demand for the same flux and heating power. Effect of controller is higher when Rm is high compared to Zm. Rm Zm INB The role of magnetic flux controllers and their effects may be explained and evaluated by composition of magnetic flux circuit similar to electric current circuit.
- 7. Improvements Expected for O.D. Coils • Improved Heat Pattern Control /Ability to Heat Difficult Areas (axle fillet, etc.) • Better Utilization of Power in Workpiece for short static coil (energy savings up to 30%) • Lower Coil Current and therefore reduced losses in supplying circuitry – transformer, capacitors, busswork • Shielding of part and machine components from unintended heating • For long OD coils (one example is multi-turn forging coils)– small or no coil parameter improvement. However, in some cases local temperature control and shielding is required • Heat treating of some difficult parts can not be achieved without application of flux controller 7
- 8. Magnetic Flux Control Example of ID Coil 8 Φ = IN / (Zm + Rm) Φ – Magnetic Flux causing heating IN – Ampere turns of the coil Zm – Magnetic resistance of the “active zone” Rm – Magnetic resistance of return path, i.e. space inside the coil Magnetic core reduces Rm by permeability times and for an ideal core Rm => 0. Then Φ = IN / Zm
- 9. Multi-Turn Cylindrical Hair-pin Coil Single-Turn Cylindrical ID Coils with Magnetic Cores 9
- 10. Improvements Expected for I.D. Coils • Shorter heating time • Substantial energy savings (oftentimes 40-50% or more) • Strongly improved electrical efficiency • Drastically reduced current demand • Reduced losses in power supplying circuitry • Heat pattern control Single-turn I.D. induction coil with Fluxtrol A concentrator 10
- 11. Influence of Magnetic Core on ID Coil Parameters IsovaluesResults Quantity : Equi flux Weber Phase (Deg): 0 Line / Value 2 / -165.8672E-6 3 / -126.9004E-6 4 / -87.9336E-6 5 / -48.9668E-6 6 / -9.9991E-6 Color Shade Results Quantity : |Current density| A/(square mm) Phase (Deg): 0 Scale / Color 5.39815 / 7.75897 7.75897 / 10.11979 10.11979 / 12.4806 12.4806 / 14.84142 14.84142 / 17.20224 17.20224 / 19.56306 19.56306 / 21.92387 21.92387 / 24.28469 24.28469 / 26.64551 26.64551 / 29.00632 29.00632 / 31.36714 31.36714 / 33.72796 33.72796 / 36.08878 36.08878 / 38.44959 38.44959 / 40.81041 40.81041 / 43.17123 Magnetic field lines and temperature maps for the coils with and without magnetic core (right) Core Ui, V Ii, A Pi, kW Eff- cy Coil kVA Yes 46 875 12.0 84 40 No 44 1850 14.3 70 81 Coil head parameters Account for losses and reactive power in the coil leads and supplying circuit shows additional benefits of the core 11
- 12. Single turn ID inductor with Fluxtrol A core Examples of Optimized ID Coils 12 Quenchant External cooling Coil copper cooling Fluxtrol core with quench holes 4-turn ID inductor with Fluxtrol 50 core
- 13. Effects of Magnetic Flux Controller on Hairpin Coils • Magnetic resistance of the back path is mainly due to limited space between the coil legs • Central pole is critical; side poles are less important though they further reduce current demand • Application of MFC to a part of the coil provides strong control of power distribution in the part along the coil I Rm Zm/2 Zm/2 /2/2 I 13
- 14. Improvements Expected for Hairpin and Transverse Flux Coils • Shorter heating times • Substantial energy savings • Greatly improved heat pattern control • Drastically reduced current demand • Reduced losses in power supplying circuitry • Transverse flux heating - possibility to provide uniform heating in the edge areas Example of concentrator influence when applied to hair-pin coil (see details on next slide) 14
- 15. Other Coil Styles Where Concentrators Improve Performance Dramatically • Pancake Coil • Split-n-Return • Vertical Loop • Single-Shot • Channel Coils • Transverse Flux Heating Coils • Any coil where there is limited space for back path flow of magnetic flux + + . . 15
- 16. Considerations for Magnetic Controller Material Selection Electromagnetic characteristics: • Magnetic permeability • Saturation flux density • Electrical resistivity • Losses • Operating frequency Thermal characteristics: • Thermal conductivity • Temperature resistance Mechanical characteristics: • Mechanical strength • Hardness • Machinability • Conformable Others • Ease of installation • Chemical resistance • Special characteristics • Overall costs etc. Importance of individual characteristics strongly depends on application type 16
- 17. Magnetodielectric Fluxtrol Materials • Properties depend on magnetic particle type and size, binder type and manufacturing technology • Magnetic permeability may be in a wide range from several units to more than hundred • Can work in 3D magnetic fields • Can work in the whole frequency range of induction heating applications • Come in either solid, machinable type (Fluxtrol or Ferrotron) or formable type (Alphaform) • Fluxtrol and Ferrotron MDMs have excellent machinability • Due to mechanical properties may be used as structural components of induction coil assembly • Easy to apply and modify in field conditions • May be custom designed to meet specific requirements • Specific properties of Fluxtrol and Ferrotron materials and technology of their application to induction coils are described in the next chapter 17
- 18. Laminations • Very high permeability (thousands in weak fields) • High temperature resistance, which depends mainly of electrical insulation of sheets • High saturation flux density (1.8 T) • Limited to low frequency (below 30 kHz) • More difficult to provide intensive cooling • Application is very laborious especially for complex coil geometry • Difficult to machine • Poor performance in 3-D fields • Rusting and expansion/deformation when overheated 18
- 19. Ferrites • High permeability in weak fields (up to tens of thousands) • Can work at high frequencies • Low losses in selected grades • Low saturation flux density (0.3-0.4 T) • Low Curie temperature (~ 250 C) with magnetic properties reduction starting at 150-200 C • Poor thermal conductivity • Very poor mechanical properties – High hardness – Brittle – Non machinable with conventional tools • Sensitive to mechanical impacts and thermal shocks • Inconsistent dimensions (large tolerances) from manufacturer 19
- 20. General Guidelines for Selecting the Right Type of Concentrator Material Determine requirements and conditions for a given application – Induction coil geometry • Coil made from Formed Tubing (Alphaform) or Machined Copper (Fluxtrol or Ferrotron) – Magnetic properties of material – Frequency, power and duty cycle – Lifetime of inductor – Time to get material – Time to manufacture coil – Ability to reproduce coil easily Vertical Loop induction coil with a pile of laminations and Fluxtrol block 20
- 21. 21 Fluxtrol Machinable Products • All materials have excellent machinability • Can work in three-dimensional magnetic fields • Frequency ranges and resistivity values are only for reference •Ideal Solution for Machined coils, or coils with rectangular tubing
- 22. 22 Magnetic Permeability of Fluxtrol Products Materials are quasi-linear especially Ferrotron 559 Fluxtrol A material supports permeability above 50 at flux density up to 14000 Gs Permeabilities don’t drop with frequency: Fluxtrol A up to 70 kHz; Fluxtrol 50 up to 500 kHz; Ferrotron 559 up to 15000 kHz Permeability vs Flux Density 0 25 50 75 100 125 0 3000 6000 9000 12000 Flux Density, Gs Permeability Ferrotron 559 Fluxtrol 50 Fluxtrol A
- 23. 23 Standard C-shaped Concentrators Besides of round and rectangular shapes, standard C-shaped concentrators are available They are made of Fluxtrol LRM of two types: LRM LF and LRM HF C-shape concentrators have optimal material orientation and dimensions that fit majority of standard tube sizes. They may be used at low frequencies instead of laminations or at high frequencies where concentrators are not used at all. Examples of LRM concentrators
- 24. Alphaform Formable Products • Alphaform materials are formable magnetic flux controllers. Alphaform comes in 3 grades designed for use at different frequencies: LF (1-80 kHz), MF (10 - 450 kHz) and HF (20 - 3000 kHz). These materials are a good alternative to the traditional machinable Fluxtrol and Ferrotron materials for complex shaped induction coils manufactured with formed tubing. In these applications, the Alphaform adheres to the contours of the induction coil to ensure good heat transfer between the concentrator and the water cooled copper. 24 Alphaform applied to an ID Coil
- 25. 25 Magnetic Permeability of Alphaform Products
- 26. Applying Alphaform Products • Applying Alphaform to an induction coil is a relatively simple, 3 step process. The first step is to conform the material to the areas of the induction coil you desire to enhance the heating of. The next step is to constrain the material so that it will maintain it's shape through the curing process. The final operation is to bake the material in the oven to cure the material to finalize the geometry. After curing, the Alphaform is no longer formable and is a mechanically strong material, much like our machinable products. 26
- 27. Permeability Influence 27 A – side areas, B – work area Gap 4 mm; Coil face width 19 mm Frequencies 3 and 10 kHz Workpiece: • Flat body composed of a central part B and two side areas • Materials – magnetic or non-magnetic steel Conditions: • Linear single-turn inductor • Same temperature under the coil face • Same heating time Considered parameters: 1. Current demand 2. Power demand
- 28. Coil Current Demand versus Concentrator Permeability 28 Coil Current vs. Perm. 50 kW In Part Under Coil Face 0 1500 3000 4500 6000 7500 1 10 100 1000 Current(A) Permeability Magnetic parts Non-magnetic 3 kHz 10 kHz
- 29. Results: Total Power vs. Permeability Concentrator reduces power demand 25 - 30% at permeability 20 - 40. Notice: no improvement at higher permeability for all studied cases Total Power vs. Perm. 50 kW In Part Under Coil Face 50000 60000 70000 80000 90000 100000 110000 120000 130000 140000 150000 1 10 100 1000 Rel. Perm Power(W) L1cm-Mag-gap4mm-3kHz L1cm-Mag-gap4mm-10kHz L1cm-Non-gap4mm-3 kHz L1cm-Non-gap4mm-10kHz Permeability Magnetic part Non-magnetic part 29
- 30. Performance of Fluxtrol vs. Lams 30 Fluxtrol LRM provides the same heat pattern on the plate as laminations
- 31. Magnetic Control in Crankshaft Hardening • Crankshaft hardening involves local heating of the bearing and/or fillet region of a crankshaft • Magnetic controllers should always be used on crankshaft coils for – Heat pattern control • Shape of Pattern • Balance between areas w/wo counterweights • Oil hole compensation – Efficiency improvement – Reduction of part distortion 31
- 32. Non-rotational Crankshaft Hardening 32 Fluxtrol shields Magnetic Coupler SharP-C inductor with Fluxtrol side shields courtesy of INDUCTOHEAT Inc.
- 33. No shielding Side shielding Complete shielding & concentration Magnetic Field Shielding of Crankshaft Coil 33
- 34. Hardening without magnetic controller 34 Temperature at the end of heating and martensite % distribution after hardening Flux 2D program + Metal 7 Confidential Property of Fluxtrol Inc.
- 35. Hardening with Magnetic Controller 35 Temperature at the end of heating and martensite % distribution after hardening Flux 2D program + Metal 7
- 36. Simulation Results 36 Parameters No Controller Side Controllers C-shaped Controller Current, A 4.35 4 3.5 Voltage, V 27.6 30.8 31.2 Electrical Efficiency, % 94 93 92.5 Coil Power, kW 67 54.7 51 Coil kVAs 123 123 109 Notes: • With controller the required power is significantly lower in spite of a formal reduction of electrical efficiency • For stationary heating the concentrators/shields can compensate influence of the crankshaft throws and webs on hardness pattern
- 37. Life Time Increase for U-shaped Coil by Replacing Laminations with Fluxtrol A 37 Part of U-shaped coil with Laminations Part of U-shaped coil with Fluxtrol LRM Courtesy of Norton Manufacturing Life time of coils with Fluxtrol LRM is almost doubled
- 38. U-Shaped Coil for Fillet Hardening 38 12 L Diesel Crankshaft
- 39. Conclusions • Magnetic Flux Controllers are a very important component of the induction heat treating coil design • Magnetic Flux Controllers have a beneficial effect on many types of inductors • Fluxtrol, Ferrotron and Alphaform materials work well in induction heat treating applications 39
- 40. Thank you! 40 More Information More information about magnetic flux control, controllers and application technique may be found on www.fluxtrol.com