JPH02271504A - Interface transformer core - Google Patents

Abstract

PURPOSE: To enable the production of an So interface transformer based on the request of an ISDN while having the volume as little as possible, simple winding structure and a little number of turns by using noncrystal Co base alloy, which is equipped with specified permeability and reduces magnetostriction, as magnetic core materials. CONSTITUTION: The noncrystal Co base alloy, which is equipped with permeability larger than 25000 and smaller than 95000 and reduces magnetostriction, is used as the magnetic core material. The Co base alloy has an extremely low magnetostriction value and reduces a permeability drop caused by stress in the material. It is especially profitable to use the Co base alloy mainly containing Fe and Mn totally from 3 atomic % to 8 atomic % and metalloid totally from 24 atomic % to 29 atomic % in addition to Co. Thus, the compact transformer satisfying the request of the ISDN can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a magnetic core for an interface transformer for use in a digital transmission device.

[Prior art] The coupling capacitance is as low as possible at 20kHz.
This type of interface transformer with an inductance L greater than 0 mH is used in integrated services digital communication networks (
In the so-called SO interface of ISDN), transformers are used at the interface between the network termination and the individual terminal equipment.

ISDN is a new global digital communications system. In the I5DN, the coupling between the digital local exchange and the network termination takes place via the UkO line interface. In this case, the distance between the digital local exchange and the network termination can be at most 8 km. Up to eight terminal devices can be connected to one network terminal. The terminal device can be, for example, a telephone, a videotelephone, a videotex, a facsimile, a fax, a workstation, etc. Again, the terminal equipment can be separated by up to 150 m from each network termination. The interface between the network end and the terminal equipment is called the SO user interface.

The requirements for such an interface are based on the international standard CCITT 1.430 or the German Federal Post Office standard FT.
It is defined in Z I TR230. These standards define the impedance of the interface in relation to the frequency of the transmitted digital pulses or the pulse mask. Regarding the requirements for the magnetic and electrical characteristics of interface transformers based on these standards, see e.g.
ffner Elektronik), Rutherbach, Switzerland, company publication PURL 1101E, written by H, Hemphil!
Using pulse transformers for SDN applications
Pulse Transformers for
ISDN-Appli-cation) J. FIGS. 2 and 3 of this f-11 document show requirements for impedance and pulse transmission based on post office standards. Whether a digital pulse can be transmitted within a predetermined pulse mask is primarily related to the inductance and capacitance of the transformer. The inductance L° of the transformer primarily determines the top tilt of the transmitted pulses. Top tilt is an undesirable decrease in the transmitted pulse voltage that occurs during a pulse. The inductance of the transformer must exceed approximately 20 m H to meet the requirements of l5DN, the capacitance of the transformer affects the signal shape of the transmitted pulses, especially when transitioning from high to low levels. . A value as low as possible is required for the coupling capacitance. Coupling capacitance refers to the capacitance between two different windings of a transformer.
The coupling capacitance depends in particular on the number of turns provided and on the winding arrangement. For example, an RM B m core is shown in said publication as a magnetic core for a So interface transformer. Ferrite is specified as the magnetic core material. For magnetic permeability and saturation magnetic flux density Bs when using ferrite
The value for is restricted. A typical value for this is extension=10000. Bs=0.45T (see Siemens' 5IFERIT 38).

The inductance of the transformer is directly proportional to the magnetic permeability of the magnetic core material. Particularly in the case of DC initial magnetization of transformers, a relatively large core cross-section or a large number of turns is required in order for the permeability and saturation flux density values of the ferrite to satisfy the ISDN requirements for inductance. . However, a large core cross-sectional area means an increase in the size of the core and therefore the volume of the transformer. However, parts as small as possible are desired. A large number of turns means an increase in coupling capacitance and therefore a deterioration in transmission characteristics. To avoid this, a complicated winding structure with an insulating layer sandwiched between the windings is required. This makes the manufacture of the windings complicated and expensive.

[Problem to be Solved by the Invention] An object of the present invention is to make it possible to manufacture a <So interface transformer based on the requirements of ISDN by having a volume as small as possible, a simple winding structure, and a small number of turns. The object of the present invention is to provide a magnetic core for a So interface transformer. In particular, it is intended to satisfy ISDN requirements even in the case of direct current initial magnetization of the transformer.

[Means for solving the problem] This problem is based on this invention, and is based on the present invention.
This problem is solved by using an amorphous Co-based alloy with a magnetic permeability greater than 0 and less than 95,000 and low magnetostriction. Co-based alloys have very low magnetostriction values. This means that the decrease in magnetic permeability due to stress in the material is very small.

The magnetic core according to the invention allows the production of compact interface transformers with small dimensions. This interface transformer meets the requirements set by the standards due to its hour wheel winding structure. In particular, this transformer is
The required value for the inductance is achieved even in the case of an initial magnetization as expected due to the asymmetric current distribution in the SDN network. In the case of Co-based alloys with g>95,000, the permeability is already significantly reduced with small initial magnetizations, so that the required inductance can only be achieved with a relatively large core cross-section or a high number of turns. If the magnetic permeability g<25,000, the required inductance can likewise be achieved only by the above measures.

It has proven particularly advantageous to use Co-based alloys which, in addition to Co, mainly contain a total of 3 to 8 atomic % Fe and Mn and a total of 24 to 29 atomic % metalloids. 5
Amorphous Co-based alloys with metalloid contents in the range from ~35 at. % are described, for example, in EP 21101 and DE 302 153
It is known from Publication No. 8. However, C with a metalloid content of less than 24 atom % or more than 29 atom %
It has been found that o-based alloys do not meet the requirements for initial magnetic permeability. Metalloids include B, Si, C and P.
becomes a problem.

The combination of B and St has proven advantageous, in which case B can be partially replaced by C. With the addition of Mn, the core according to the invention meets the I SDN standard for the So interface even in the case of the initial magnetization as expected in a transformer at the end of the network; furthermore, this amorphous Co-based alloy % or less N
It can contain one or more of MO1Cr or Nb in an amount of up to i and l atomic %. However, cores with the greatest tolerance for initial magnetization are obtained with Co--Fe--Mn metalloid alloys when the Mn content is at least 0.5 atomic %. After extensive research and testing, it has been discovered that this type of Co-based alloy in particular is a suitable core material for ISDN interface transformers.

In this type (7) Co-based alloy, metalloid-containing ff1Z is for magnetic permeable wheels, Fe-containing ia, Mn-containing, N
i-containing ic, Mo-Cr-Nb-containing ff1d, B or C
It is given by the following equation in relation to the content lx.

18+1.41ogA+B <z <18+1.7-7
-1o+B where 1-μ(1+0.25(a+c)) B=0.25(a-b)-0.2cmd+3.2m With the magnetic core based on this invention, the So interface transformer is It can be manufactured with a magnetic core cross-sectional area of less than 0.2 cm 2 on the terminal device side, and with a magnetic core cross-sectional area of less than 0.1 cm 2 with respect to the terminal device side.

[Examples] Next, the present invention will be described in detail with reference to drawings and tables showing a plurality of examples of magnetic cores based on the present invention.

FIG. 1 shows the interfaces and inductive devices in the ISDN, which are the UK line interface between the digital switching center 1 and the network termination (NT) 2, and the network termination 2 and the terminal equipment (TE) 3. and the SO user interface between.

A UKO interface transformer 4 is used for the transmission of information between the digital switching center I and the network termination 2. The processing of the digital signals at the network termination 2 is performed by an electronic device 5. The network terminal is further connected to the N of the So interface.
A T-interface transformer 6 is provided. The transmission of digital signals between network termination 2 and terminal equipment 3 takes place via transmission line 7.8 and reception line 9.10. T on terminal device 3
The signal is converted via an E-bain-face transformer 11 and processed by an electronic device 12. The terminal device further comprises a current-compensated interference prevention choke 13.

The magnetic core according to this invention has a So interface of NT
It is used in the interface transformer 6 and the TE vane-face transformer 11. The power supply to the terminal device takes place in part from the digital switching center via the So user interface. This applies, for example, when the terminal device is a telephone. The remote power supply of the terminal device is not shown in FIG. 1; the remote power supply takes place via the center tap 14 of the NT interface transformer 6. In the ideal case, which does not correspond to the actual situation, the feed current can be applied to the transmitting line 7.8 or the receiving line 9, I
distributed in the same proportion to O. However, in reality different current paths have different resistances. Possible causes for this are, for example, different winding resistances of the transformer and different resistances of the plug contacts of the connecting cords of the lines or terminals. Such asymmetry of the currents in the transmission line 7.8 or in the reception line 9.10 results in an initial magnetization in the NT interface transformer 6 or the TE vane-face transformer 11 of the So interface, due to thorough studies and calculations thereof. , about 3 mA for TE vane-face transformer 11
It turns out that the initial magnetizing current of should be taken into account. In comparison, the expected maximum initial magnetizing current in the NT interface transformer 6 is very large. This is because up to eight terminal devices can be connected in parallel at one network end. For this purpose an initial magnetizing current of up to about 12 mA is expected.

In order to guarantee the standard-required transmission of digital pulses that fall within the prescribed pulse mask range, the transformer must have an inductance of more than 20 mH even for the above-mentioned initial magnetizing current, as well as a coupling capacitance. Should be small. The upper limit for this is approximately 1009
It can be considered as F.

In the following examples, amorphous magnetic core materials were produced in the form of thin tapes by melt rotation quenching. A toroidal core was wound from an amorphous strip, the manufacturing method of which is well known and is not the subject of this invention. The toroidal core was subsequently heat treated in a transverse magnetic field, ie, a field parallel to the axis of rotational symmetry of the toroidal core. The magnetic core was heated for this purpose to a temperature of approximately 420'C and subsequently cooled at a cooling rate of 0.1-3/min. The magnetic core based on this invention is 0.3・1O-6
It has a magnetostrictive value of less than This means that the reduction in magnetic permeability due to stress in the material is very small.

Example 1: Co-Fe-M alloy Alloy composition Go88.2 Fe4Si based on the above method
A magnetic core with 18.8 Bll was manufactured. 0,2.
Various cooling rates of 0.4 and 1.0/min were selected. Table I shows the measured saturation flux density Bs and initial permeability for a frequency of 20 kHz, and A magnetic field strength Ho is stated which decreases to 70% of the value of magnetic flux. The magnetic field strength Ha, together with the initial magnetic permeability, provides information about suitability as a metamorphic bond material in the presence of initial magnetization. A small Ho value means that it is only suitable for small initial magnetizations.

It was found that the initial permeability increases with the cooling rate, while the magnetic field strength Ho decreases accordingly.

Based on the expected initial magnetization, HO is not allowed to be less than 70 mA/cm for the NT interface transformer 6 and the TE vane Approximately 20mA in case of face transformer 11
The premise is that it is not allowed to be smaller than /cm. This alloy is therefore suitable for both interface transformers based on its Ho value.

Example 2: Co-Fe-Me-M alloy surface treatment includes alloy No. 2.1 to 11.1, Co, F
e, alloys containing Mn as an auxiliary in addition to metalloids are described. The magnetic core according to No. 2.1 to 2.3 is 950
The corresponding Ho value is clearly 20 mA/
cm, this core is not suitable for the interface transformer, whereas cores 3.1 to 10.3
all have an initial permeability within the range of 25,000 to 95ooo. In the case of these cores, the heat treatment has the same effect on permeability and Ha as in the case of the core of Example 1. However, the value of Ho always exceeds 20 mA/cm regardless of the cooling rate during heat treatment. No. 11.1 describes a magnetic core having an alloy composition outside the scope of the claims. The metalloid content in this example is 20! tK%. The Hoc7) value is very high at Ho=5060, but the initial permeability is too small at g=1000, so according to this core, the requirements for the interface transformer can only be met by increasing the core cross-sectional area or the number of turns. be able to.

Example 3: Co-Fe-T-M alloy coat II describes the magnetic value of a magnetic core made of an alloy that does not contain Mn. These alloys are supplemented with 1.5 at%
It is found by comparison that these cores containing Mo have smaller Ho values than the core containing Mn described in Example 2. Therefore, a Mn-free Mo-doped magnetic core can be advantageously used for the TE Zeinface transformer 11. By suitable heat treatment, as shown in core No. 14.1, particularly high Ho values can also be achieved, such that it is possible to employ this core in the NT interface transformer 6.

FIG. 2 graphically shows the relationship between metalloid content and initial permeability. The values of the group shown in the square are the composition Co remaining Fe3.2 Mn1 (SiO, 6B0.4)
Regarding the alloy of z. The values of the group indicated by an asterisk are the set tC
o Remaining Fe3.8 No1.5 (Si0.8 Bo, 4)
Regarding the alloy of z. From this graph it can be seen that particularly advantageous range limits for the metalloid content are shown in relation to the contents of the other alloying components and the initial permeability.
Fe Mn Ni T (Si (B
, C) ) remaining abcdl-x
where T is at least one of the elements rvio, cr, or Nb, and the individual metal component ratios of the magnetic core based on this invention are shown by the following equations.

3 <a+b <8, c <15, d <1, 0
．． 3 <x <0.7 For the permissible metalloid content of the core, 18+1.4-4-1o+B <z <
18+1.7・logA+8 where A=μ(1+0.25(a+c)) B=0.25(a-b)-0.2cmd+3.2x 3rd
The figure shows the Mn-containing magnetic core described in Example 2 and the Mn-containing core described in Example 3.
The graph shows the relationship between Ho and initial permeability for a magnetic core that does not contain Mn as described in a The graph shows that the Ho value increases with the addition of Mn. It is possible to achieve Ho values that clearly exceed the HO of a magnetic core without a magnetic core. Mn-containing alloys are therefore advantageous core materials for loaded interface transformers. Therefore, Mn-containing alloys are particularly advantageous as core materials for interface transformers with a large DC initial magnetization.

Example 4: In another extensive study, amorphous Co-based alloys containing various combinations of Fe, Mn, Ni and Mo additions were investigated. The results are summarized in Table ■. The initial permeability was again measured at a frequency of 20 kHz. As the results show, with these magnetic cores 25000-95
Magnetic permeabilities in the range of 0.000 can be achieved. This often requires relatively high cooling rates, which are technically difficult to realize, especially during heat treatments.

Cr or Nb also has the same effect as MO. Therefore, suitable magnetic cores include Co, Fe, Mn and metalloids as well as Ni.
, Mo, Cr or Nb. However, alloys which do not contain the last-mentioned alloying elements are preferred.

Example 5: A transformer was completed with a magnetic core having the alloy composition described in Example 2.3. The transformer had two windings with the same number of turns. The completed device is 9.8X6.
It had dimensions of 8x5mm. The inductance and coupling capacitance C of the transformer were measured for the case of L (0) without DC initial magnetization and for the case of initial magnetization with DC at I=2.5 mA. The results are summarized in Table ■. No. of Example 2, 2N=34 already due to the magnetic core of 3.2
For a total number of turns of , an inductance of more than 20 mH was obtained even at a DC initial load of 2.5 mA. Inductance could be increased by increasing the number of turns. At the same time there was a particularly slight increase in the coupling capacitance.

Sufficient inductance and small coupling capacitance were obtained with magnetic core No. 5.3.6.3.7.3. These magnetic cores have a magnetic permeability of 67,000 to 86,000. Ho values range from 26 to 45 mA/Cm.

Furthermore, a transformer was manufactured using the Mn-free magnetic core of Example 3 No. 12.1. This magnetic core is only 15 mA
It has a Ho value of / cm. For this reason, 2.5m
The required inductance for a DC initial load of A could not be achieved with a total number of turns of 2N=34.38 or 42. However, in the case of a transformer having a total number of turns of 2N=46.50.54, the specifications were satisfied. However, these transformers are disadvantageous for economic reasons due to their large number of turns.

FIG. 4 graphically shows the relationship between inductance and DC initial load for transformers with No., 3.2 and 12.1 cores. 2x19 each on the magnetic core
A turn is attached. Magnetic core No. 3 containing Mn
．． The transformer with Mn-free magnetic core No. 12
．． It shows a clearly higher DC initial load than the transformer with 1.

A transformer with a magnetic core No. 3.2 containing Mn meets the requirements of ISDN up to a DC initial load of approximately 5 mA in the configuration described, this core can therefore be used in particular as a TE interface transformer 11. .

Example 6: A transformer was fabricated using magnetic cores No. 1.2.7.1.9.2.1O02, 11.1 and 27.1. These transformers again had two windings with the same number of turns. The dimensions of the completed device were 14X7X6mm. Inductance L when there is no initial magnetization (0
) and the inductance and coupling capacitance C for a DC initial load of 12 mA were measured. Measurement is 20kHz
It was carried out at the frequency of z. The results are summarized in Table V.

Transformers with magnetic cores No. 1.2.7.1.9.2 and 10.2 already have very good values of inductance and coupling capacitance for a small total number of turns, for example 2N=38. Was. These transformers are therefore I
Due to the high direct current initial loading capacity of these transformers, which meets the requirements of SDN, these transformers can be employed in particular as NT interface transformers 6. The permeability of the magnetic cores taken as examples is between 34,000 and 39,000. The Ho value is in the range of 90-108 mA/cm. A comparison with the values of Example 5 reveals that for relatively high DC initial loads a core with a relatively low initial permeability and a relatively high Ho value must be chosen. This also applies to the magnetic core No. 11.1 listed in Table V.
and 27.1. With these cores, which are not within the scope of this invention,
Only with a total number of turns of 120 or 200 will the requirement for inductance be met. However, this large number of turns again leads to very large coupling capacitances, so that in order to reduce the coupling capacitance in the case of these transformers it is necessary, for example, to insert insulating layers between the windings, which is costly. Therefore, an expensive winding structure is required.

FIG. 5 shows the relationship between inductance and DC initial load for two transformers with magnetic cores No. 9.2 or 14.1. The transformer is 2X19 turf (2N=
38).

A transformer with a magnetic core No. 14.1 that does not contain Mn is:
Meets the ISDN requirements for inductance up to a DC initial load of about 10 mA, whereas No. 9.2
A transformer with a magnetic core containing Mn of 14 mA satisfies the ISDN requirements for inductance up to a DC initial load of about 14 mA, and therefore, for given assembly dimensions and number of turns, the latter can be adopted as an NT interface transformer 6. can do. FIG. 5 once again makes clear the superiority of Mn-containing cores in the case of high DC initial loads.

Therefore, with the magnetic core according to the present invention, it is possible to manufacture a very compact transformer that meets the requirements of ISDN. No, Ma (store) Fe Bs Rui H.

(T)
3 38 90 0.83 43 84 2.1 0.2 2.2 0.4 2.3 1.0 3.3 17.3 11 0.58 10B 0.58 118 0.58 130 3.1 0. 2 3.2 Q, 4 3.3 1.0 3.3 11 0, [to 85 430.80 7
8 34 0, Eio 93 22 4.1 0.2 3.5 1 1B, 7 11
0. EiO45734,20,40,Bo 57
534.3 1.0
0. EtO75325,10,23,4116,7
Table I! No, v Fe Mn (Nu) Bs Rui H.

(↑) X103 (Bai) 8.1 0.2 3.3 1 1B, 7 11 0.
Ell 48 B28.2 0.4
0.81 81 50
B, 3 1.0 0.
81 80 3012.1 0.23.8 0
+, 5 18.311.20.53 7B 1
512.2 0.4
95 1412.3 1.0
103 1
2? , 1 0.2 3.2 1 1B,? 11
0. B2 39 927.2 0.4
0.82 49 70?
,3 1.0 0.8
2 B? 4513.1 0.23.8 0
1.5 18.3 +113.2 0.4 13.3 1.0 0.54 8.1 8.2 0.2 0.4 3.1 1 1B, 7 11 0.82 41
790.82 4i3 82 9.1 0.2 3.3 1 1B, 4 11 0.
B4 29 1419.2 0.4
0.84 3B 1059.
3 1.0 0.
84 49 8914.1 0.23.8 0
1.5 1[1,31014,20,4 14,31,0 0,59 10,10,23,211B,3 11 0.65
27 13EiIQ, 2 G, 4
0.85 34 10B10.
3 1.0 0.6
5 44 8711.1 1.0 1.5 Table m No. v Fe Mu Ni No S
i (1M B 83 Rui (T)
1.00 15.3 2.00 1B. 1 0.40 1.5 3.81G. 2
1.00 1El. 3 2.00 17.1 1.00 2.4 21? ．． 2 2
．． 00 0 1.3 15.3 9.7 0.85
1B0.85 19 0.85 27 01.215 15.8 1l 0.69 11 0.89 14 0.89 17 0.88 30 0.88 38 1B. 1 0.40 0 1B. 2 1.00 l3 19.1 1.00 2.1 519.2 2
．． 00 l5 20.1 0.40 2.3 4.5 10 0
20.2 2.00 l3 0.70 110 1.70 190 0.87 20 0.67 25 0.71 12 0.71 21 21.1 0.40 2.3 4.5 1021
．． 2 2.00 22, 1 1.00 0.4 7.5 1022
．． 2 2.00 23.1 0.40 0 23.2 1. Qθ 23.3 2.00 7.5 l0 24.1 0.40 0 24.2 1.00 ? ,5 25.1 1.00 1. ? 525.2 2
．． 00 l4 26.1 t. oo o 7.5 27.1 1.00 1.1 12.5 12.5 0.85 480.85
80 0 11.5 11.5 0.71 250.
71 33 11.5 11.5 0. fl8 290.6B
45 0. El8 47 O l2 l2 l2 0.84 102 0.84 120 0.64 32 0. fl4 44 O 10.8 10.8 0.83 13.2 B. 5 0.82 Table ■ No 2N L L (I snow 2.5 layers A) Table V No, 2N 3.2 3.2 3.2 3,2 ml mH 9.2 9,2 9.2 1.2 a8 L (0) mH L (1=12mA) mH 2B 5.3 10.2 7.1 6.3 2B 3l 7.3 12.1 12. l 12.1 12. l 12. l 12. l 14.1 14. l l4.1 14.1 27.1 27.1 11.1 11.1

[Brief explanation of drawings]

Fig. 1 is a wiring diagram of an ISDN interface, Fig. 2 is a graph showing the relationship between metalloid content and initial magnetic permeability of an alloy for a magnetic core based on the present invention, and Fig. 3 is an example 2 of the alloy. A graph showing the relationship between the magnetic field strength Ho and the initial magnetic permeability at which the magnetic permeability decreases to 70% of the initial magnetic permeability for Alloys No. 3.2 and No. 3. A graph showing the relationship between inductance and DC initial load for transformers, Figure 5 is for alloy No. 9.2 and N
FIG. 2 is a graph showing the relationship between inductance and DC initial load for a transformer manufactured by O.14.1. 1...Digital switching center 2...Network termination 3...Terminal equipment 6.11...8 factors between the interface transformers 8 = engineering♀♀in ω? NO Fig, 4

Claims (1)

[Claims] 1) A magnetic core for an interface transformer with as little coupling capacitance as possible and an inductance L exceeding 20 mH at 20 kHz for use in a digital transmission device, with a magnetic permeability of more than 25,000 and less than 95,000 as the core material. A magnetic core for an interface transformer, characterized in that an amorphous Co-based alloy with low magnetostriction is used. 2) The amorphous Co-based alloy contains, in addition to Co, mainly Fe and Mn in a total of 3 to 8 atomic % and metalloids of 24 to 29 atomic %, and in some cases further up to 15 atomic % of N.
i and 1 atomic % or less of Mo and/or Cr and/or N
The magnetic core according to claim 1, characterized in that it includes b. 3) The Co-based alloy has the following composition Co_RemainingFe_aMn_bNi_cT_d(Si_1_
−_x(B,C)_x)_z, where T is the element M
o, Cr, or Nb, and the following formula holds true for the alloy composition (atomic %): 3<a+b<8 c<15 d<1 0.3<x<0.7 18+1.4・log A+B<z<18+1.7・lo
gA+B where A=μ(1+0.25(a+c)) B=0.25(a-b)-0.2c-d+3.2x The remainder is Co and impurities, μ is the initial permeability, and logA
3. The magnetic core according to claim 2, wherein is the common logarithm of A. 4) The magnetic core according to claim 3, characterized in that the proportion of Mn exceeds 0.5 at % (b>0.5). 5) The magnetic core according to claim 3, wherein the magnetic core material does not contain Ni (c=0). 6) The magnetic core material does not contain Mo, Cr or Nb (d=
6. The magnetic core according to claim 3, characterized in that: 0). 7) Magnetic core according to claim 1, characterized in that the amorphous Co-based alloy has a magnetostriction value of less than 0.3.10^-^6.