Designs for High
Current Applications
Donna Kepcia
Technical Sales Manager
Applications for
High Current Inductors
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Solar Power Conversion
UPS systems
Hybrid & Electric Vehicles
Wind Power Conversion
Transportation
Three-phase chokes
Large output chokes
Products for High Current Applications
POWDER CORES
Kool Mµ® Toroids 62, 74, 102, 133
and 165 mm
Kool Mµ® E and U cores 65 –160 mm
Kool Mµ® and XFLUX ® Blocks – Create
custom shapes
XFLUX ® Toroids
FERRITES
New large
geometries
What is a “High Current”
Inductor Application?
50 Amps 600 uH
150 Amps
84 uH
300 Amps
60 uH
Design Goals:
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35 kHz
400 Hz
6 kHz
Target inductance achieved at maximum load
Low temperature rise
Lowest cost
Smallest size
Examine the constraints
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Frequency of operation
Allowable Temperature Rise
Cost
Size and weight
Geometry
Conductor type
Powder Core Material
Comparison Table
Material Characteristics
High frequency
Low Core cost
Low Losses
Readily available sizes
Larger design
Kool Mm
XFlux
Lower frequency
Medium Core cost
Higher Core Losses
Lower Copper Losses
Compact Design
High
Flux
Smallest
Design
All
frequencies
Low Losses
More variety
of perms
Higher cost
Inductor design specifications
Solar inverter
DC current 50 Amps
AC ripple 5 A p-p, RMS ripple 3.5 A
Rated inductance 600 uH at 52.5 A
Ambient temperature 25oC
Acceptable operating temperature 110oC
Temp rise 85oC allowed
LI2= 1,500, Frequency 35 kHz
Design Process High Flux Toroid
• Calculate LI2
– Peak current (A) & inductance needed at
that current (mH).
• Use chart to select core with LI2 in range
• Determine first cut turns
• Determine mmf
√
N=
H=
L * 106
AL
NI
le
50 A Design
0058337A2
Current Inductance
50 Amps
600 uH
LI2
1,500
0058337A7
26
68 +/- 8%
Al = 68 mH/1000 turns; +/- 8%
68 mH – 8% = 62.6 mH/1000 turns
N=
Ae = 0.678 cm2
le = 32.4 cm
√
N = √(L in mH X 106 / Al)
L * 106
AL
N = √(0.6 mH X 106 / 62.6) = 96 turns
H in Amp-Turns/cm = (N turns X I in Amps) / 9.84 cm
H = ( 96 Turns X 50 A ) / 32.4 cm = 148 A-T/cm
High Flux DC Bias Chart
Determine inductance roll-off for High Flux using
calculated mmf
148 Amp-Turns/cm
About 79%
Design Iterations – Recalculate roll off
96/ 0.79 = 122
H = (122 X 50A) / 32.4 cm = 188 A-T/cm
Put the values back into the equation to make
sure that the number of turns selected
achieves target inductance under the peak
DC bias condition.
L in mH = (%H X N2 X AL ) / 106
0.670 mH = ( 0.72 X 1222 X 62.6 ) / 106
Meets requirements for Peak DC bias. Turns
could be reduced.
Software Kool Mu
0077165A7
300 Amps
60 uH
6 kHz
UPS
Output
Inductor
Block Inductor Design
• Kool Mu
• 150 Amps, 84 micro henries, 400 Hz
– 3 Copper Air cores replaced with Kool Mu
blocks
– Total system losses were
decreased by 900 watts from
3500 watts to 2600 watts
for a 25% reduction in losses.
– Cabinet size will be reduced
saving material.
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


Full load Inductance 80 uH
Rated Current 150 Amps rms
Inductance at low current 84 –0%/+5% uH
Inductance (between 0 and 300 amps peak) Nominal 10%/+10% uH
Inductance (between 300 and 450 amps peak) Nominal
–25%/+10% uH
Maximum 400 Hz current Rated rms +5% Amps rms
Maximum 10 KHz current 18% of Rated rms Amps rms
Maximum 20 KHz current 6.5% of Rated rms Amps rms
Calculate the Number of Turns Required, N:
 N = (L*I pk*10)/(B max*Ac), N=26
 N = (0.084*212A*10)/(0.375T*18), N=26
 L = 84 uH , Target is 80 at peak
 I pk = 212 amps (nominal maximum peak
current = 1.414 * 150 amps).
 B max = 0.375 Tesla (3750 Gauss). Chosen
so that at absolute maximum peak current
of 450 amps B max stays below 0.8 Tesla
 Inductance to drop no more than15% below
initial at 300 A.
 Ac = 18 cm2
• Keep the windings away from the core by 0.125”;
3.175 mm to minimize losses.
• Foil used to support 150 – 200 Amps was 0.019”;
0.482 mm.
•
Paper used was 0.003”; 0.076 mm thick.
• A thickness of 0.007”; 0.178 mm was added to each
wrap to compensate for inability to achieve 100%
efficiency with the wraps.
• Total area needed for winding: 26 X .029” + 0.125”
= 0.754” = 19.1 mm. thick
3.75”; 95.25 mm wide
Block Design for One Inductor
Air gaps
16.0 cm
90 mm
30 mm
60 mm
105 mm
30 mm
Air gaps
15 mm
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P core (mW/cm3) = F(KHz)1.60 * B(Kilogauss)2.0
Volume of core = 26 blocks * 27 cm3 /block = 702 cm3
This is the equation for the 26 permeability material.
Assuming a flux density of 3.8 KG (0.38 Tesla) at 400 Hz
18% of this at 10 KHz, and 6.5% of this at 20 KHZ, we calculate:
P core (mW/ cm3) = (0.4)1.6 * (3.8)2.0+ (10)1.6 * (3.8*0.18)2.0+ (20)1.6 *
(3.8*0.065)2.0
= 3.33 + 18.63 + 7.36 = 29.3
P core loss = 29.3 mW/cm3 * 702 cm3 = 22 W
Conclusions:
‣ Reduction in System Power Consumption by replacing 3 air
cores by Kool Mu blocks—900 Watts.
‣ 700 was the combination of core losses and induction heating
in the case from 1015 to 315 watts.
‣ Dimensions of the block inductors: 7.75”L x 4.6”W x 3.9”H
‣ Dimensions of the air core inductors: 6.75”L x 6.75”W x 9.5”H.
‣ Air core inductors require an additional 3” air perimeter away
from metal
‣ Weight of block inductor is 15 lbs vs.16.5 lbs for air core.
‣ Cost of the new inductor is about 10% lower than the air core.
‣ Much higher cost savings are achieved because of lower
power losses (easier to cool) and being able to make the
overall unit smaller. Being smaller, lower cost, and 25% more
energy efficient makes the unit more attractive to the end user.
# Turns
# Blocks
of foil
Block type
Current
Inductance
46
46
46
16
16
16
4741 26m
4741 26m
4741 26m
50 Amps
100 Amps
125 Amps
335 mh
250 mh
210 mh
46
46
46
46
30
30
30
30
4741
4741
4741
4741
26m
26m
26m
26m
50 Amps
75 Amps
100 Amps
150 Amps
550 mh
475 mh
413 mh
313 mh
100
50
25
12
12
12
8030 26m
8030 26m
8030 26m
50 Amps
100 Amps
200 Amps
800 mh
200 mh
49 mh
AL Calculation adapted from
MMPA geometrical guidelines
2
AL = 4πAeµ/ le
Calculations
Ae = C1/C2 cm2
Ie = C12/C2 cm
AL Calculator for Block Structures
A
B
C
D
E
L
A1
A2
A3
Millimeters 8 4741
backwall
150.0
one leg
47.5
thickness
41.0
D one core
20.0
Window width 95.0
Leg width
27.5
1127.50
1127.50
1127.50
2255.00
2255.00
2255.00
3382.50 1306.25 2612.50 3918.75 1050.00
3382.50 1127.50 2255.00 3382.50 1050.00
3382.50 1306.25 2612.50 3918.75 1050.00
A4
(C*L+C*(B-D))/2 1127.50
2255.00
3382.50 1216.88 2433.75 3650.63 1050.00
A5
(C*L+C*(B-D))/2 1127.50
2255.00
3382.50 1216.88 2433.75 3650.63 1050.00
40.00
190.00
40.00
43.20
43.20
40.00
190.00
40.00
43.20
43.20
40.00
190.00
40.00
43.20
43.20
41.0
190.0
41.0
69.51
69.51
41.0
190.0
41.0
69.51
69.51
41
100
190
160
41
100
69.5077 47.1239
69.5077 47.1239
0.3161
0.0003
0.1580
0.0001
0.1054
0.0000
0.3455
0.0003
0.1728
0.0001
0.1152
0.0000
l1
l2
l3
l4
l5
C*L
C*(B-D)
C*L
16 4741 24 4741 10 4741 20 4741 30 4741 6 8030
150.0
150.0
190.0
190.0
190.0
140.0
47.5
47.5
61.5
61.5
61.5
80
82.0
123.0
27.5
55.0
82.5
35.0
20.0
20.0
20.5
20.5
20.5
50
95.0
95.0
95.0
95.0
95.0
80.0
27.5
27.5
47.5
47.5
47.5
30
2*D
2*E
2*D
p/4(L-(B-D))
p/4(L-(B-D))
C1
C2
# Blocks
le
Ae
Ve
Perm
Al calc
Al = 4pAeu/le
0.4326
0.0004
8 blocks 16 blocks 24 blocks 10 blocks 20 blocks 30 blocks 6 blocks
35.64
35.64
35.64
40.97
40.97
40.97
45.42
11.28
22.55
33.83
11.86
23.72
35.57
10.50
401.83
803.67 1205.50 485.83 971.67 1457.50 476.96
26
26
26
26
26
26
26
103.4
206.7
310.1
94.6
189.1
283.7
75.5
3800
3800
3800
3895
3895
3895
8000
mH/1000T
Window area mm2
Block Series
Sizes currently available: – 47 X 41 – 55 X 28
– 50 X 30 – 60 X 30 – 70 X 30 – 80 X 30
• New sizes can be tooled
• Limits roughly 80 X 30 mm; 49 X 49 mm
20.0 mm
0.79”
50.5 mm
1.98”
30.3 mm
1.19”
15.0 mm
0.59”
00K5030B
Recommended Adhesive and Dispensing system
Bondmaster
Elantas
LOCTITE® ESP109
Air-powered Dispensers
By using controlled air pressure and
microprocessor-based timers – instead
of operator guesswork – to regulate the
amount of material applied to each
part, Nordson EFD's air powered
adhesive dispensing systems eliminate
variability in benchtop dispensing
processes.
Kool Mu
100 AT/cm
200 AT/cm
XFlux
100 AT/cm
200 AT/cm
40 mu 26 mu
55%
78%
% initial
26%
50%
perm
40 mu 26 mu
82%
92%
% initial
47%
70%
perm
XFlux
00X4741B
00X5030B
00X6030B
00X8030B
Kool Mm
26m, 40m
26m, 40m
26m, 40m
26m, 40m
00K4741B 26m & 60m
00K5030B 26m, 40m & 60m
00K5528B 26m, 40m & 60m
00K6030B 26m, 60m & 90m
00K8030B 14m, 26m, 8030BHT35 26m,40m, 60m
Thank you for your time!
Suggestions?
Questions?