The document discusses the development and application of composite magnetic controllers for induction coils, particularly highlighting the new material Fluxtrol 75 which has enhanced thermal conductivity. It emphasizes the importance of temperature prediction and management in maintaining reliable inductor performance, detailing methods for thermal control. Additionally, the document presents simulation techniques for predicting temperature distribution and the benefits of internal cooling in preventing overheating.

1. TEMPERATURE PREDICTION
AND THERMAL MANAGEMENT
FOR COMPOSITE MAGNETIC
CONTROLLERS OF INDUCTION
COILS
V. Nemkov, R. Goldstein, J. Jackowski, N. Vyshinskaya, C. Yakey
Fluxtrol, Inc., 1388 Atlantic Blvd, Auburn Hills, Michigan 48326,
USA

2. Overview
• Composite Magnetic Controllers for
Induction Coils
• Specialty Material Fluxtrol 75
• Temperature Prediction via Computer
Simulation
• Methods of Temperature Control
• Examples of Application
• Conclusions

3. Composite Materials for Magnetic
Controllers
Fluxtrol magnetic composites are premium materials widely
used in induction devices due to excellent machinability, ability
to work in 3D field and at any frequency (even at 13.56 MHz)
Temperature prediction and management are very important
for reliable performance of inductors
Controller temperature depends upon its geometry,
magnetic losses, material thermal conductivity and
boundary conditions
New specialty material Fluxtrol 75 with high thermal
conductivity was recently developed in addition to three
main materials (Fluxtrol A, Fluxtrol 50 and Ferrotron 559)

4. Specialty Material Fluxtrol 75
10000 80
μ
70
8000
60
6000 50
B, Gs
40
4000
30
2000 20
H, A/cm
10
B, Gs
0 0
0 20 40 60 80 100 120 140 0 2000 4000 6000 8000 10000
Formulated for middle to high frequencies (30-400
kHz), it has maximum permeability of 75 and saturation
flux density 1.5 T. Due to high permeability and thermal
conductivity (λ = 0.16 W/cmK) it can be effectively used
for heavy loaded HF applications 4

5. Composite Material Anisotropy
All pressed composites have certain anisotropy!
Pressing
direction
A B C
Particle deformation and
Orientation C is optimal due to lower
orientation during pressing
losses and higher heat transfer
Fluxtrol A: λ ᅩ = 0.2 W/cmK λ ॥ = 0.06 W/cmK

6. Thermal Management
Controller temperature prediction and
management are very important for reliable
performance of inductors
Methods of thermal control:
- Favourable coil design
- Optimal material selection
- Material orientation
- Gluing technology
- Cooling plates
- Internal cooling

7. Prediction of Magnetic Controller
Temperature in 2D Case
I1
25.4 I2
Glue
I3 I1
I2
I1
In Flux 2D: I1 – I3 - boundary conditions
Step1: EM simulation and mapping magnetic field distribution
Step2: Controller area discretization for subdomains with appr.
constant B and extracting of Bavg vector

8. Prediction of Magnetic
Controller Temperature
Step 3: Calculation of a vector of magnetic loss power
density Pv
Pv = c B a fb
c – coefficient specific for material
a and b – values of flux density and frequency
dependencies a = 2-2.2, b = 1-1.25
If magnetic field has two components, the coefficients c1
and c2 can characterize the anisotropy in the calculation of
the vector of magnetic loss power density Pv
Pv = (c1B1a + c2B2a) fb

9. Prediction of Magnetic
Controller Temperature
Step 4: insertion of magnetic
losses into Flux 2D and
calculation of temperature
distribution with account of proper
boundary conditions In
In Flux 3D:
Formulae for losses Pv vs. B
and f can be inputted directly Max T = 90 C
into the program
Temperature in coil copper and
Fluxtrol A concentrator at 20 kHz; the
part power is 80 kW per half meter

10. Prediction of Magnetic
Controller Temperature
III
Max T = 193 C Max T = 127 C
Non-optimal orientation (A) Optimal orientation (C)
Temperature distribution in coil copper and Fluxtrol 75
concentrator at 200 kHz; part power is 80 kW per half meter

11. Induction Coil Parameters
Coil length is half meter
Frequency Orienta Ppart Pcu Pconc Ptotal Tconc U I
(kHz) tion (kW) (kW) (kW) (kW) max (V) (A)
20 C 80 23 1.7 104 90 0C 183 4000
200 C 80 24.7 4.2 108 127 0C 878 2190
200 A 80 25 5.8 109 193 0C 877 2200
• Orientation of the concentrator material influences its
temperature without notable influence on coil parameters
• Relative losses in concentrator grow significantly with
frequency

12. Induction Coil with Cooling Plates
Cooling
plate
Extended
Cross
Legs
Rated coil parameters: Frequency 150 kHz, Bm = 400 Gs
U = 660 V, I = 3500 A, S = 2300 kVA, Q = 90

13. Controllers with Internal Cooling
Sandwich of two plates with cooling channels (left)
and a single plate with water connector (right)

14. Magnetic Bridge with Internal
Cooling
Bridge with cooling channel Illustration of Bridge setup for
welding with multi-turn inductor
Magnetic Bridge improves welding quality and allows to
increase welding speed 25-30%

15. Summary
• Composite magnetic materials may be effectively
used in the most challenging applications
• Computer simulation can predict the controller
temperature with good accuracy
• Several methods of thermal management may be
used to prevent controller overheating
• Internal cooling is one of the most effective
methods
• More information about composite magnetic
materials may be found @ www.fluxtrol.com