Gapped Cores
How To Order
Part Number
Gapping for AL
0P44317
A450
Same as for ungapped cores
Gap Code
When specifying and ordering E cores (including EC, EFD, EER, ETD, and Planar E cores) gapped
to an AL, it is important to note which cores are produced in gap-to-gap combination, because two
gapped pieces are assembled to achieve the AL. Alternatively, for E cores provided ungapped-togap, an ungapped piece must be used with a gapped part to achieve the AL. Pot, RS, DS, RM,
PQ, and EP cores are sold as sets whether the combination is gap-to-gap or ungapped-to-gap.
Gap Code
The letter indicates the type of gap and a three-digit number defines the value.
Code
In most applications, defining the gap with the AL results in inductors with the least variation.
Electrical measurement is inherently more precise, and compensation is made for variability in
material permeability and core geometry.
Meaning
Example
A_ _ _
AL (if <1000)
DF42311A275
(AL=275)
X_ _ _
AL if 1000 or greater
(add 1000 to code)
OP44721X250
(AL=1250)
F_ _ _
AL if <100, non-integer
(divide code by 10)
OR42510F807
(AL=80.7)
G_ _ _
Depth of Grind in mils
(1000ths of an inch)
OF44317G079
(Gap=0.079”)
M_ _ _
Depth of Grind, mm
(divide code by 10)
OF43019M015
(Gap=1.5 mm)
AL is inductance factor, mH/1000 Turns, or nH/T².
Either the AL or the depth of grind (not both) is controlled during production of gapped cores.
See the chart on pages 14-15 for tolerances.
Gap-to-Gap vs Ungapped-to-Gap Core Sets
“Gap-to-gap combination” means the gap is symmetrical. Half of the total gap is removed from
each piece.
“Ungapped-to-gap combination” means an asymmetrical gap; the entire gap is taken from one
piece, and the other piece is ungapped.
12 Gapped Cores - MAGNETICS
AL testing and limits are calculated to three significant digits, based on the normal value. For
example, AL=99±3% is interpreted as 96.0 Minimum, 99.0 Nominal, and 102.0 Maximum.
Magnetics tests gapped AL values with full bobbins, usually 100 turns, or 250 turns for deep
gaps. The drive level is low (5 Gauss) and the frequency is set low enough to avoid resonance
effects. Measured inductance in an application may vary significantly from the theoretical value
due to low turns, low bobbin fill, leakage effects, resonance effects, or elevated drive levels.
It is important for the users to verify the correlation between the test of the core and the specific
test being applied to the inductor or transformer. Planar E cores, Planar RM, and Planar PQ cores
are especially susceptible to correlation discrepancies.
Gapping for Depth of Grind
For parts ordered in pieces (E and I cores). The depth of grind is given for each piece.
For parts orders in sets, the depth of grind is given as a total for the set, and may be ungappedto-gap core pieces, or gap-to-gap. To make an ungapped-to-gap set, use one piece of each. For
example, use 0R41808G050 with 0R41808EC for an asymmetrical gap of 0.050”± 0.001”.
For the same gap, but symmetric, use two pieces of 0R41808G025.
For deep gaps, however, better consistency often results when the depth of grind is specified.
In such cases, variation in the finished inductor is dominated by the variation in the windings,
especially if the number of turns is low.
Gapped Cores
AL Value Tolerances
Size
Gap to Gap
±3%
Ungapped to gap combination
±3%
±5%
±7%
±10%
Pot Cores
40704
40905
41107
41408
41811
41814
42213
42616
43019
43622
44229
25-35
25-48
25-75
71-113
96-174
65-135
113-204
139-249
170-304
222-399
169-389
Page 46
36-62
49-87
76-135
114-210
175-326
136-340
205-482
250-695
305-1015
400-1494
390-1965
!95
!135
!220
!307
!523
!510
!779
!1125
!1642
!1999
!1999
!125
!180
!285
!417
!712
!700
!1060
!1543
!1999
!283
!400
!708
!731
!998
!1485
!1999
!1999
!385
!525
!963
!994
!1369
!1999
RS (Round-Slab) Cores
41408
41811
42311
42318
42616
43019
43622
44229
25-39
25-39
25-39
25-39
25-62
40-62
40-62
25-177
40-270
40-347
40-452
40-622
63-918
63-1286
63-1732
Page 52
DS (Double Slab) Cores
42311
42318
42616
43019
43622
44229
109-195
78-135
117-205
149-264
170-300
179-315
196-386
136-441
206-580
265-873
301-1111
316-1543
!175
!240
!399
!574
!988
!980
!1459
!1999
!530
!800
!1325
!1378
!1884
Page 52
!625
!706
!930
!1412
!1797
!1999
!850
!961
!1276
!1922
!1999
!1170
!1332
!1756
!1999
Size
Gap to Gap
±3%
Ungapped to gap combination
±3%
±5%
±7%
±10%
PQ Cores
42016
42020
42610
42614
42620
42625
43214
43220
43230
43535
44040
45050
60-184
50-139
200-396
110-334
95-296
77-234
127-416
128-409
84-241
89-255
83-230
128-210
Page 48
185-467
140-467
397-777
335-645
297-888
235-880
417-548
410-486
242-808
256-980
231-1006
210-1999
!755
!754
!1258
!1044
!1436
!1423
!885
!1369
!1305
!1575
!1625
!1027
!1026
!1728
!1421
!1955
!1936
!1207
!1878
!1775
!1999
!1999
RM Cores
41110
41510
41812
41912
42316
42819
43723
25-50
56-98
69-120
69-120
84-150
126-200
145-250
Page 50
51-55
99-162
121-238
121-238
151-395
201-625
251-977
!75
!258
!381
!381
!633
!1002
!1580
!170
!352
!519
!519
!862
!1374
!1999
EP Cores
40707
41010
41313
41717
42120
!1425
!1422
!1999
!1972
!1999
!1999
!1661
!1999
!1999
!250
!484
!714
!714
!1195
!1892
Page 44
25-50
25-55
25-75
25-100
25-180
51-75
56-75
76-110
101-175
181-450
!125
!125
!175
!275
!630
!275
!400
!850
!160
!160
!315
!630
!1250
Chart shows type of combination and the guaranteed tolerance for corresponding AL ranges. Ranges indicated are the tolerances for standard gapped. For ± 5%, ± 7%, and ± 10%, the maximum AL for each
is shown. Standard cores are manufactured to the smallest allowed tolerances.
www.mag-inc.com
15
Gapped Cores
AL Value Tolerances
Size
Gap to Gap
±3%
Ungapped to gap combination
±3%
±5%
±7%
±10%
E Cores
41203
41205
41707
41808
41810
42510
42515
42520
42530
43007
43009
43515
43520
44011
44016
44020
44022
44317
44721
45528
45530
45724
46016
46527
47133
47228
48020
49928
Page 24
16-27
28-47
22-37
27-42
44-74
37-61
28-43
107-190
45-72
42-67
55-91
54-87
65-111
59-95
52-83
78-126
94-156
81-136
107-180
113-186
150-360
129-218
102-129
142-235
150-285
120-199
99-158
150-285
28-55
48-107
38-89
43-121
75-235
62-200
44-210
191-397
73-409
68-307
92-222
88-429
112-461
96-642
84-545
127-916
157-1187
137-762
181-1188
187-1736
361-285
219-350
130-1231
236-500
286-525
200-1823
159-1922
286-550
!86
!170
!140
!192
!376
!318
!333
!643
!655
!491
!353
!687
!738
!1029
!872
!1480
!1903
!1222
!1920
!1999
!480
!450
!1999
! 682
!775
!1999
!1999
!745
80-438
99-627
124-911
136-1403
!702
!1004
!1471
!1999
!117
!229
!190
!258
!512
!432
!452
!874
!891
!668
!475
!934
!1003
!1400
!1185
!1999
!1999
!1676
!1999
!160
!316
!259
!355
!704
!595
!616
!1202
!1225
!919
!653
!1284
!-1380
!1940
!1629
!650
!550
!1040
!850
!900
!1040
!1999
!1650
!925
EC Cores
43517
44119
45224
47035
!1999
Page 28
49-79
61-98
76-123
83-135
!954
!1365
!1999
!1312
!1891
Size
Gap to Gap
±3%
Ungapped to gap combination
±3%
±5%
±7%
±10%
EER/ETD Cores
43434
43521
43939
44216
44444
44949
45959
55-88
54-86
95-156
71-117
73-117
81-130
51-118
Page 30, 36
89-500
87-566
157-641
118-876
118-881
131-1075
119-1822
!806
!913
!1028
!1415
!1423
!1736
!1999
!1095
!1241
!1398
!1925
!1935
!1999
30-90
31-81
46-220
67-296
91-450
!130
!127
!350
!475
!790
!170
!172
!430
!646
!975
EFD Cores
41212
41515
42019
42523
43030
18-29
19-30
29-45
41-66
50-90
Page 32
ER Cores
40906
41126
41426
41826
42313
43021
15-65
40-74
45-84
50-84
55-90
80-169
19-35
17-31
18-32
35-66
78-141
118-216
119-222
173-315
106-189
201-367
169-305
266-481
379-701
336-594
66-70
75-100
85-130
85-200
91-200
170-710
!110
!140
!190
!325
!525
!1050
!150
!190
!250
!445
!710
!1460
!200
!275
!380
!650
!900
!1975
Page 38
36-76
32-77
33-205
67-188
142-405
217-643
223-673
316-956
190-507
368-1130
306-1130
482-1496
702-1999
595-1999
!122
!123
!329
!304
!656
!1040
!1088
!1547
!821
!1828
!1828
!1999
*These tolerances also apply to Planar E-I combination.
14 Gapped Cores - MAGNETICS
!230
!236
!575
!888
!1125
Page 34
Planar E Cores*
41425
41434
41805
42107
42216
43208
43618
43808
44008
44308
44310
45810
46410
49938
!1507
!1707
!1935
!1999
!1999
!166
!167
!448
!414
!892
!1427
!1491
!1999
!1116
!1999
!1999
!228
!230
!617
!569
!1239
!1964
!1999
!1548
Gapped Cores
Depth of Grind Tolerances
Tolerance Ranges for Pot, RS, DS, RM, PQ, and EP cores
Inches
Millimeters
Gap
Tolerance
Gap
Tolerance
Gap Condition
0.001”– 0.038”
±0.0005”
0.1 mm– 0.9 mm
±0.03 mm
Ungapped to gap combination
0.039”– 0.076”
±0.001”
1.0 mm– 1.9 mm
±0.04 mm
Ungapped to gap combination
(Except if the gap is more than 10% of the minimum bobbin
depth for the set*, then gap-to-gap combination.)
0.077”– 0.114”
±0.002”
2.0 mm– 2.9 mm
±0.07 mm
Gap to gap combination
(Except if the gap is less than 10% of the minimum bobbin
depth for the set*, then ungapped-to-gap combination.)
0.115”– 0.152”
±0.002”
3.0 mm– 3.8 mm
±0.07 mm
Gap to gap combination
0.153”– 0.228”
±0.004”
3.9 mm– 5.0 mm
±0.12 mm
Gap to gap combination
*The bobbin depth for the set is the 2D dimension or 2 times the D dimension
Tolerance Ranges for E, EC, ER, EER, EFD, ETD and Planar E cores
Inches
Millimeters
Gap
Tolerance
Gap
Tolerance
0.001”– 0.038”
±0.0005”
0.1 mm– 0.9 mm
±0.03 mm
0.039”– 0.076”
±0.001”
1.0 mm– 1.9 mm
±0.04 mm
0.077”– 0.152”
±0.002”
2.0 mm– 3.8 mm
±0.07 mm
0.153”– 0.228”
±0.004”
3.9 mm– 5.0 mm
±0.12 mm
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13