Magnetics Core Loss - psma.com...Mar 23, 2016 · Wednesday March 23 2016 1. Introduction Core loss...
Transcript of Magnetics Core Loss - psma.com...Mar 23, 2016 · Wednesday March 23 2016 1. Introduction Core loss...
High Frequency Magnetics; Black Magic, Art or Science?
Magnetics Core Loss
Dr. Ray Ridley
APEC Industry Session on Magnetics
Wednesday March 23 2016
www.ridleyengineering.com1
Introduction
Core loss calculations and measurements
New core material needs
Need for extensive data
Approximations to data
Different excitation waveforms
Temperature variations
Standardized data base proposals
2© 2016 Ridley Engineering Inc
Immediate Goals for Core Materials
10K 100K 1 M 10 M 100 M
CORE
LOSS LIMITEDSATURATION LIMITED
FERRITE
MPP
0.3 T
0.6 T
Would be nice to at least extend saturation range further
Frequency (Hz)
SATURATION
LOSS
Improvements
3© 2016 Ridley Engineering Inc
B-H Loop and Core Losses
Core loss calculations and measurements
© 2016 Ridley Engineering Inc 4
H
B
𝛥𝐵
Core Loss MPP 200u
300 kHz 0.1 T 5 W/cm3
5000 mW/cm3
© 2016 Ridley Engineering Inc 5
Core Loss PC95
300 kHz 0.1 T 0.350 W/cm3 > 10 times better than MPP
350 mW/cm3
© 2016 Ridley Engineering Inc 6
Core Loss Steinmetz Equation
Steinmetz equation can
be used to approximate
the actual loss measurements
Three coefficients define the
loss for a given material
© 2016 Ridley Engineering Inc 7
x
c
yP fk B
Steinmetz Equation Limitations
© 2016 Ridley Engineering Inc 8
x
c
yP fk B
Equation assumes curves are
1) Equally spaced with frequency
2) Equal slopes at different frequencies
Modifying the Steinmetz Equation
Discrete step changes in coefficients from Mag Inc.
a c d<100 kHz 0.074 1.43 2.85
100-500 kHz 0.036 1.64 2.62
>500 kHz 0.014 1.84 2.28
© 2016 Ridley Engineering Inc 9
x
c
yP fk B
Steinmetz Equation Changing Coefficients
© 2016 Ridley Engineering Inc 10
x
c
yP fk B
k x y<100 kHz 0.074 1.43 2.85
100-500 kHz 0.036 1.64 2.62
>500 kHz 0.014 1.84 2.28
Ridley-Nace Variable Steinmetz Equation
1.729 ( 0.00076 2.8332)( 3.626ln 28.32) f
cP f f B
Continuously-variable coefficients with Ridley-Nace formula
Five coefficients needed to describe materials
Example for Magnetics R material:
© 2016 Ridley Engineering Inc 11
( )( ln ) c d
c
efP f f Ba b
Continuously Variable k Term
12
0.01
0.1
1
10
100
1000
10000
0.005 0.1
Magnetics R Material Measured Core Loss
0.01 0.2
3/mW cm
Loss
Flux Density T
Frequency
200 400 600 800 10000
0
20
16
12
8
4
3.626ln 28.32k f
Measurements
( )( ln ) c d
c
efP f f Ba b
3.626 28.32a b
Continuously Variable y Term
13
0.01
0.1
1
10
100
1000
10000
0.005 0.1
Magnetics R Material Measured Core Loss
0.01 0.2
3/mW cm
Loss
Flux Density T
Frequency
200 400 600 800 10000
0
3
2
1
0.00076 2.8332y f
( )( ln ) c d
c
efP f f Ba b
© 2016 Ridley Engineering Inc
0.00076 2.8332d e
Oliver Variable Steinmetz Equation
(Powdered Iron Core Material)
14
2 2
3 2.3 1.65
core da b c
fP f B
B B B
Continuously-variable coefficients with Oliver formula
Four coefficients needed to describe materials, plus 2.3 and
1.65 exponents subject to change with different materials
www.micrometals.com/appnotes/appnotedownloads/coreloss update.pdf
© 2016 Ridley Engineering Inc
Core Loss Temperature Variation
15
Six coefficients needed to describe temperature variation
Every material has a different curve
Does the curve also change with frequency and flux level?
-60 0 60 120
Temperature
1
2
3
4
5
Loss Multiplier
5 4 3 2
5 4 3
1
2
0( )g T T T T T Ta a a a a a
Manufacturer’s Data
© 2016 Ridley Engineering Inc
Different Core Excitations
16
Need to modify equations to suit each of these waveforms
B
t
B
t
B
t
B
t
© 2016 Ridley Engineering Inc
General Triangular Flux Waveform
1 2
1 22 2
( ) fcD
c fcD
P D PD DP
B
t1 sDT 2 sD TsT
2 B
( )( ln ) c d
c
eff f Ba bP
17© 2016 Ridley Engineering Inc
Duty Cycle Core Loss Multiplier
1 2
1 22 2
( ) fcD
c fcD
P D PD DP
0
1
2
3
4
5
6
0 0.1 0.2 0.3 0.4 0.5 0.6
B = 0.15 T
: 'DCM D D
: ' 1CCM D D
18© 2016 Ridley Engineering Inc
Putting it All Together
19© 2016 Ridley Engineering Inc
What We Need from the Manufacturers
1) Raw core loss sinewave test data over wide range of
frequency, B, temperature
2) Who is going to fund the modeling into a standard
format database?
20
Magnetics Forecast
High-ripple current inductor designs will dominate the practical high-performance market
Practical “high performance” means converters up to 5 MHz
Core material improvements will be just incremental (unless some breakthrough material emerges)
Insufficient funding is going into fundamental magnetic material research to give a
good chance of any breakthroughs.
Data Standardization is badly needed from the core manufacturers to ease confusion
Core loss raw data is needed, not just curves.
Creative core geometries need to be applied to POL inductors and other high-ripple parts
Magnetic core will not go away (however much it is wished for)
Isolation transformers will creep back into PoL applications to boost efficiency – More magnetics!
Multi-converter processing will continue to proliferate.
© 2016 Ridley Engineering Inc 21
Some References
Cliff Jamerson: Targeting Switcher Magnetics Core Loss Calculations,
Power Electronics Technology, Jan 2001.
Ed Herbert: http://www.psma.com/technical-forums/magnetics/core-loss-studies
Christopher Oliver: www.micrometals.com/appnotes/appnotedownloads/coreloss update.pdf
Power Supply Design Center Articles http://www.ridleyengineering.com/design-center.html
[89] Core Loss Modeling
[90] Core Loss Modeling with Non-Sinusoidal Waveforms - Part II
[91] Core Loss Modelling - Sinewave Versus Triangle Wave - Part III
Ray Ridley and Art Nace
[A03] Modeling Ferrite Core Losses
Christopher Oliver
[A06] Core Loss Modeling & Measurement
Power Supply Design Software http://www.ridleyengineering.com/software.html
22© 2016 Ridley Engineering Inc