DE3546410C2 - - Google Patents

Description

The invention relates to a Power transformer in jacket design according to the Preamble of claim 1.

Such a transformer is from EP application 01 26 365 known. With this transformer is the Primary winding divided into two partial windings, the encase the secondary winding. The windings are as foil windings with intermediate Insulations carried out. This transformer is called Switching transformer used. Despite the use of an open type ferrite core are characterized by the Foil windings the parasitic inductances of this Transformers kept small. Also allow the Foil windings a compact design with a Reduction of the magnetic leakage flux. The Most of the magnetic flux is on this Steered in the ferrite core, with practically none Air gaps must be overcome.

The known transformer can only be used for relatively small Services are used because of higher services enhances the relaxation properties of the Core material come into play. Especially when high Services with also high frequencies in Medium frequency range should be switched these characteristics lead to severe distortion of the transmitted impulses.

From US-PS 36 17 854 is a power transformer known for switching operations with frequencies around 30 kH is suitable. The one wrapped around the core Primary winding made of foil or bifilar winding wire  is surrounded by two secondary section windings, the first secondary part winding closely on the primary winding and the second secondary section winding closely on the first Secondary part winding and close to the outer web of the core is wrapped. In addition, the secondary part windings with each other and with mass over a die Diode circuit connected to the switching behavior too improve. Because of this winding configuration also with this transformer the main part of the Transfer energy through the nucleus so that the mentioned relaxing properties of the Core material despite the additional diode circuit do not allow optimal impulse transmission.

From DE-PS 18 02 830 is a low scatter Transformer, especially for pulse transmission known in which the windings as alternating arranged partial windings of the primary and Secondary windings from only one layer of film exist, the location of the primary and Secondary winding combined in parallel and the number of which is such that the current load in the locations a maximum permissible value exceeds. Such transformers are for the Resistance transformation and resistance adjustment have been developed, in particular the frequency response improved in audio frequency transmissions by power amplifiers should be. This happens through the layers Winding and thereby reducing the average Distance between primary and secondary winding, because this distance is approximately proportional to the leakage inductance is. What is essential in such transformers linear transmission range in acoustic  Frequency range that starts below the mains frequency and ends at about 20 kH. As core materials at such transformers laminated dynamo sheets used. Play in this frequency range gyromagnetic frequencies on which the mentioned Relaxation properties with the negative influences do not yet matter.

From the Valvo Techn. Inf. TI 83 11 125 from 1983 it is known, windings not only in layers, but to nest in blocks; see. there the sections 7.2 and 7.3. From this is also known the leakage flux and Eddy current losses through the use of Reduce film windings. By appropriate Nesting of the secondary winding by one Primary winding can thus the maxima of the stray fluxes be reduced.

After all, it's from Mark: R-L-C-Components Handbook 1959, p. 116, known to a conventional Lamella core a winding configuration of two Secondary windings and a primary winding to arrange, the primary winding of the Secondary windings is sheathed. Is this sheathing accordingly tight and thus the coupling accordingly well, the secondary part windings are in the range of highest flux line density. This too Transformer is used in the audio frequency range. Due to the tight winding coupling with the core, it is not as a power transformer for high Suitable switching frequencies.  

Transformers become conventional using the following formula dimensioned:

in which
n number of turns,
U voltage (V),
B magnetic flux density (10 ^-4 T),
A core cross-sectional area (cm ² ),
f frequency (s ^-1 ) and
4 is the form constant for square wave stress.

The core cross section is selected from the point of view of the power to be transmitted. The transmission power of conventional transformers, which contain the known magnetic materials, decreases with increasing frequency, as illustrated in FIG. 1. This decrease in power, which places limits on energy transmission with increasing frequency, is based on an increasing deviation of the actual effective transmission power from the theoretical transmission power of the transformers with increasing frequency. The deviations are extremely large. If, for example, based on the core mass and other transformer data, a theoretical transmission power of 4 kW is calculated at a transmission frequency of 25 kHz, then in a practical exemplary embodiment of a transformer, an actually achievable transmission power of 1 kW results. Therefore, if certain transmission powers are to be realized with conventional transformers, this leads to power weights (W / kg), which must be increased by factors.

This problem was addressed in a data book supplement "Ferrite 82/83", June 1983 edition from Siemens AG in the Section ETD cores for power electronics, p. 4, "Transferable benefits", paragraph 2 mentions: "Depending on the requirement (Insulation, winding, current density, etc.) and Cooling options are much higher performances, however also to transmit less ". Further information on the solution are however not given.

The invention has for its object in a transformer the arrangement of the windings of the type in question also to be modified in relation to the core so that the transformer is suitable for the transmission of high energies is possible and especially in switching mode phase-free course of primary current rise and secondary voltage rise shows, the temperature load is low should stay.

This object is according to the invention by the characterizing Part of claim 1 specified features solved.

Accordingly, the spatial separation of the windings takes place from the core and through the arrangement of the primary winding on the secondary winding as well as the close coupling of the Secondary winding with the primary winding transferring energy essentially over the windings, so the influence of the core, in particular the delay properties mentioned of the core material, only slight during switching operation are. The transformer is especially for power transmission with working frequencies in the range of about 20 up to 100 kilohertz and rise times from approx. 100 to 200 Nanoseconds corresponding to a transmission range of 5 to 10 megahertz for sinusoidal AC voltages and suitable for the transmission of high power pulses. Here it is possible to provide a galvanic isolation between the Ensure circuits and both a voltage transformation as well as to enable a current transformation. The transformer has a favorable power-to-weight ratio and small dimensions and can be inexpensive and just be made. It is particularly noteworthy that despite these high powers the heating of the transformer within easily manageable limits  remains, so that cooling of the transformer is not necessary is.  

In order to arrive at the solution according to the invention, a number of measurements were carried out on transformers, in particular with regard to power transmission via the magnetic path. The measuring arrangement shown in FIG. 2 was used for this. A core 2 in EE design was selected, which had ground end surfaces in order to keep the air gap 4 as small as possible. The core had narrow, high winding chambers 6 . A primary coil 8 and a secondary coil 10 were arranged spatially separated from one another on the same inner web 12 of the core.

A measuring circuit illustrated in FIG. 3 was used to carry out experiments with the measuring arrangement shown in FIG. 2. The connections 14, 16 of the primary coil 8 were connected to a voltage generator 26 . The generator 26 was used to generate control pulses with a steep slope, the rise and fall times of which were between about 200 and 500 ns and which were, for. B. acted on sine or rectangular pulses. The output voltage of the generator 26 was variable, its internal resistance R _i small (R _i → 0). The winding of the secondary coil 10 was terminated with the connections 18, 20 by a purely ohmic resistor 30 . A fast current transformer 22 terminated by a resistor 24 served for the potential-free measurement of the primary current i _p . The primary voltage U ₁ and the secondary voltage U ₂ were measured. A fast multi-channel oscilloscope 28 was used to display the measured variables.

The investigated transformer was on the dynamic Magnetization curve up to the saturation range below Controlled increase in generator output power. Here, taking into account the hysteresis behavior of the core material (B-H characteristics) no current control allowed only to heat the winding would lead. Care was taken during the control that the proportion of direct coupling over the Winding related to the energy transfer via the magnetic Path was very small.

The measurands were especially related to the time Behavior examined. To be as quick as possible Impulse transmission, e.g. B. for frequencies up to 100 kHz and more (currently results from the usable Power transistors to allow the limit of about 100 kHz)  was a magnetic material, e.g. B. Fe-Ni sheets or Fe-Mn ferrites have been selected. The generator was further preferably with sine or rectangular pulses operated to make the behavior in the area as simple as possible to obtain the rising and falling pulse edges. The subject of the entire investigation was that the for the magnetization of the core material took time to Period of the working frequency no longer increases in one neglect.

FIG. 4 shows the time course (a) of the primary voltage, (b) of the primary current and (c) of the secondary voltage in the test measurements. The illustration of FIG. 4 (a) is shown enlarged in FIG. 5, the illustration of the rising and falling edges being illustrated for illustration purposes as being flatter than this corresponds to the actual circumstances. According to the time-exploded view of FIG. 5, is a primary voltage pulse (U _1), viewed in time, for a half cycle duration t _p of three time bands, namely, the rise time t _1, the pulse duration t ₂ and the fall time _t3. As shown in FIG. 4 (b) and (c) illustrate that is determined by the transmission characteristics of the transformer pulses of the primary current is i _p and the secondary voltage U different in timing from the timing of the drive pulses U _{1 2.} The pulse durations are shortened. The behavior over time during the rise time T ₁ and the fall time t ₃ is only determined by the switching speeds etc. of downstream components. There is no quantitative energy transfer to the secondary winding during the time t *. The secondary voltage was pulse width modulated when current flowed in the primary winding, and it was found that during the time t * there was a substantial change in flux in the magnetic circuit. Despite the flow change occurs due to effects in the core material, such as. B. Bloch-wall effects, etc., no secondary voltage. The time t * increases with the modulation on the dynamic hysteresis curve and is dependent on the magnetic material. The pulse roof of the primary current signal is shown horizontally in FIG. 4 for simplification. In reality it is clearly increasing and shows e.g. B. before the rise from the roof of the negative half-wave to the positive half-wave a negative pulse peak. As a result, the components to be designed for the maximum load can only be used effectively in a part of their operating range. Furthermore, a warming was found in the central web of the magnetic core between the primary and secondary windings, which was explained by relaxation.

The test results were based on processes in magnetic Core material returned. As already indicated, the energy conversion takes place on a transformer two ways:

• a) on the magnetic path over which the electrical Energy in electromagnetic, magnetic, electromagnetic and again converted into electrical energy becomes (preferred path in experiments) and
• b) on the path of direct coupling via the coils, where the electrical energy is electromagnetic Energy and converted back into electrical energy becomes.

In the experiments, the path was over the magnetic Material examined. The time t * represents a dead time, during the no effective energy transfer to the Secondary winding can be done because microscopic in the core material dynamic effects take place that deal with  increasing frequency noticeable. These Effects occur depending on the material (e.g. Fe, FeNi sheets, soft magnetic ferrites of different conductivity types, . . .) and different processing (different thick sheets. . .) to different degrees. It these are displacement processes in the Blochschen Walls, a gyromagnetic effect, eddy current losses, Fluctuation or Jordan after-effects and diffusion after-effects (cf. W. v. Münch, materials for electrical engineering, 4th edition, p. 16, 1983, Teubner-Verlag). The the last three effects are essentially material-related.

The conditions in the transformer are in the following Vector illustration explained.

The inductance X _{L of} the magnetic circuit filled with substances can be represented as follows:

X _L = X _LO + X _L (t) (2)

where X _{LO is} a constant term (reactance of an ideal inductance; air coil component) and X _L (t) is a time-dependent term for the flux build-up. The resistance R of the magnetic circuit filled with substances is composed of a constant term R _O and a time-dependent term R (t), which is caused by relaxation phenomena:

R = R _O + R (t) (3)

The impedance Z is therefore:

Z = jX _L + R (4)

This is illustrated in Figure 6.

The total impedance Z _tot (t) effective on the secondary side is made up of a portion of the direct coupling between the primary and secondary coils (Z _W ) and the impedance of the magnetic core material or the coupling above (Z _M ), ie composed of a winding-dependent and a material-dependent term. The material-dependent term Z _M can be represented as follows:

Z _M = jX _LM + R _M (5)

where R _{M represents} an equivalent resistance for the behavior of the magnetic core. At low frequencies, the impedance Z _{M changes} into:

Z _M = jX _LOM + R _OM - (jX _COM ) (6)

Equation (6) is the classic impedance representation, where R _{OM describes} the normal conductance of the core and X _{COM describes} the capacitive behavior of the core materials. However, the winding-dependent term in the transformer arrangement is described by the equation:

Z _W = R _W + jX _LOW - jX _COW (7)

where jX _{LOW is} constant, where X _{COW describes} the coupling _capacitance between the windings; j (X _LOW - X _COW ) = jX _W.

The total impedance Z _tot (t) can be represented by a winding-dependent, essentially constant term and a time-dependent, essentially material-dependent term:

Z _tot (t) = Z _W + Z _M (t) (8)

This is illustrated in Fig. 7. While the vector Z _W remains constant in terms of magnitude and direction, the vector Z _M changes strongly as a function of time and can assume a multiple of Z _W.

The processes in the magnetic core material are also represented by the following equation:

B = μ _o μ (t) H (9)

in which
B the magnetic flux density,
μ _o the permeability constant,
μ (t) the relative time-dependent permeability and
H is the magnetic field strength.

The permeability can be represented as follows:

μ (t) = μ ′ (t) - jμ ′ ′ (t) (10)

where μ ′, μ ′ ′ can contain constant proportions. The Phase shift

is time-dependent and indicates the instantaneous values of the phase shift between the effective permeability μ and the real permeability μ ′. The relationships are shown in FIG. 8. The time-dependent processes in the core material can also be interpreted in such a way that the core cross-section of the magnetic material no longer behaves as a constant, i.e. the portion A _{e of} the core cross-section A that is relevant for energy transfer is a function of the same core material from the beginning of a pulse Time:

where f (H, t) is a function of μ ′ and μ ′ ′. These  Function is very complicated, so the vector illustration appears clearer.

At the moment there is obviously no magnetic material on the market with the polarizations in the molecular range in time in about 500 ns in the entire linear range of Hysteresis curve are possible. An essential thought of Invention is to remedy the disadvantageous Effects of these time-dependent effects part of the Energy transfer does not take place through the core material to let d. H. to bypass the time-dependent effects. By the measurements on the aforementioned transformer resulted in the Construction of the transformer according to the invention.

Based on the above findings, a transformer in Shell construction developed, which one as gap-free as possible Core made of ferromagnetic material and at least one Has primary and secondary winding. At least one Winding is designed as a foil winding, and the Primary and secondary windings are with one in between lying insulating layer as cylinder windings on top of each other wrapped. A live partial winding of the The primary winding is always a current-carrying partial winding adjacent to the secondary winding.

In this transformer according to the invention, the power is advantageously transmitted via both paths, ie via the direct coupling of windings and via the magnetic path through the core material. An equivalent circuit for the transformer function is a parallel connection of two resistors Z _W and Z _M (t), one of which (Z _M ) changes with time. Accordingly, the energy transfer, ie the energy throughput, is time-dependent on both parallel paths. The equivalent circuit is illustrated in FIG. 9.

On the first path with direct coupling via the windings (Z _W ), the energy is transmitted electrically, then electromagnetically and then electrically again. This path is fully available without any time delay. In order to favor the energy transmission via this path, the active surface of a winding has been enlarged by designing this winding as a foil winding. Furthermore, the extent of the energy transmission has been increased by the spatial association of the windings, the proximity of which is advantageous for the efficiency of the electromagnetic energy transmission. The adjacent arrangement of current-carrying partial windings of the primary and secondary windings also serves this purpose.

The energy transfer via the second path, i.e. H. about the magnetic material is delayed due to the grain orientations, the current increase dI / dt during the reorientation, d. H. during the time t * that about 65% of the half-period for clock frequencies up to is about 100 kHz, is complex. The time-linear current increase the inductance remains after creating one Get jump function. Furthermore, parasitic inductances damped and suppressed the tendency to vibrate.

For the magnetic lines of force the magnetic Core is a preferred path outside of the coil winding area provided. Because of the slow Grain orientation takes place at high frequencies in the Secondary coil no regression of the flow change in one Tension. This means that there is no longer any induction; the phase difference increases with increasing clock frequency, and the secondary voltage remains, so to speak. The processes in the core are similar to the processes in the through Transistor. Overall, the energy transfer takes place  via the second path electrical, electromagnetic, magnetic, electromagnetic and again electrical. The dimensioning of the transformer according to the invention can be conventionally performed according to equation (1) respectively. The determination of the induction changes ΔB on the hysteresis curve and the roof slope of the impulses of the Mangetizing currents are also used in the usual way fixed. With the transformer according to the invention high powers (several kW) and currents of over 100 A. be transmitted.

By combining the two energy transmission paths is the transmission behavior of the transformer according to the invention improved. The pulse duration is extended, so that the effective energy transfer time is longer. The Switchover time from Umax to Umin and vice versa is strong, shortened in the range of less than 1 μs. This is based on the fact that the energy transfer is initially via the winding coupling (path 1) and then also via the magnetic Coupling (path 2) takes place. A time offset the output signals of the transformer according to the invention is essentially only based on the switching times of transistors used in the associated circuit etc. The transformer according to the invention therefore enables Curve shapes with extremely steep flanks up to the ns range. The pulse roof of the output signals of the transformer is very flat, essentially horizontal. The still existing sloping roof is based on the magnetizing reactive current. The lower it is, the better it is Transformer. Due to the absence of current or voltage peaks the components are in the transformer output signal the associated circuit can be better exploited because it must be designed for the maximum load.  

Another advantage of the transformer according to the invention is that that due to its better energy transfer ability its power-to-weight ratio compared to conventional transformers is significantly improved. Furthermore it comes during operation of the transformer according to the invention much less warming, e.g. B. were despite less Power applied to a conventional transformer (Output power 0.5 kW) at this 65 ° C, with the invention Transformer (2.6 kW), however, only 32 ° C temperature measured at the core. Cooling is therefore not necessary.

The core of the transformer according to the invention is as possible formed gap-free, with the columns also under cavities filled with adhesive are understood and only inevitably accepted production-related sizes will. This is done to increase the permeability μ. A magnetic core material is preferably used whose hysteresis curve is Z-shaped. Is cheap a steep B-H curve for the push-pull invention Flow converter. In an advantageous embodiment the core material of the invention is ferrite, that is very inexpensive.

A core from Wrapped tape core type proven for a wider ambient temperature range is applicable and higher requirements the material properties suffice. The Curie Temperature and induction are in this core type larger, the magnetic field strength H smaller. An advantageous one The design for the core is the E-E design. Especially it is favorable to use four U-parts, one even larger winding window results. The choice of designs and materials of the magnetic core as well as the  technical implementation or realization of the magnetic Paths are crucial for the later use of the Transformer.

It is always advantageous in the transformer according to the invention a secondary part winding between a primary part winding and the core center land arranged, whereby the winding coupling is favored. One is useful film-like formation of the insulation between adjacent Windings, which can be achieved that the Primary and secondary windings arranged close together are. This in turn improves the coupling.

To improve the winding coupling is one another embodiment of the invention between the Primary winding and the outer web of the core a secondary (partial) winding arranged. In the case of one Primary and a secondary winding the secondary winding advantageously divided into two partial windings, which the Surround the primary winding. This makes a symmetrical one Field line course of the electromagnetic field in the winding area achieved that for core-free transmission is preferred. It is particularly favorable if the winding spacing from the center bar approximately equal to the winding distance from the outer web of the core. Through this winding arrangement is achieved that the maximum force line density in Area of the winding and not in the core material.

A particularly simple design of the transformer results in only one primary and only one secondary winding itself when the primary winding on the secondary winding is wrapped.  

A particularly safe embodiment of the invention Transformer results from arranging one on both sides insulated single-layer metal foil with lead out, each between primary and secondary winding, the connection being connected to the protective conductor. This protects against accidental contact with the mains and improves radio interference immunity.

In certain applications, it is desirable to interrupt the energy transfer between the secondary and primary windings in a controlled manner, ie the energy must be keyed, quickly switched off. In this case, a single-layer, externally short-circuitable winding (preferably made of thin wires) is advantageously arranged as an auxiliary winding between the primary and secondary windings. The design of the short-circuit winding as thin as possible ensures that the distance between adjacent windings remains small so as not to unnecessarily impair the coupling factor. When using two short-circuit windings K _1,2 , the winding arrangement sees two primary and secondary windings P _1,2 and S _1,2 z. B. from: S ₁ , K ₁ , P ₁ , P ₂ , K ₂ , S ₂ (from the inside to the outside, without insulation).

In many cases it happens with conventional transformers to falsify the time course of the Secondary voltage signal with respect to the primary voltage signal. Even if the generator internal resistance goes to zero there are time-changing repercussions of the magnetic core on the secondary winding on. The operation of transformers is therefore special problematic with pulse width modulated operation, if not impossible. These difficulties are both with the new transformer as well as with conventional ones Transformers according to the invention by using short-circuitable  Fixed windings with external wiring or reduced. The latter also enables the transmission properties of the transformer, and allows in particular a lifelike, potential-free Transmission of power impulses. It even did without external wiring an improvement in the transmission behavior exposed.

The arrangement of the short-circuitable winding can also be next to the primary winding if it is designed as a wire winding and does not extend over the entire winding width, so that the associated outer secondary (partial) winding is wound onto both windings together. The associated circuit is such that the symmetrical primary winding of the transformer soft, via diodes and two push-pull switches alternately connected to a positive supply voltage at a clock frequency of about 20 to 100 kHz (at current flow I with zero internal resistance R _i and at I = 0 and also at V → 0 with R _i → 0), and the short-circuitable winding (auxiliary winding) is switched via a transistor. The additional winding is short-circuited when both switches are open, ie when neither of the two primary part windings has current flowing through them. Through electrical coupling with the transformer windings and reaction in the other windings, especially the close proximity of the auxiliary winding to the secondary winding, the targeted short circuit in the secondary winding becomes more effective than the influence of the core material. The reaction of the coil inductance is also greatly reduced. Therefore, there is no induction in the winding during this time due to the changing magnetic field. This ensures that the secondary voltage U _s goes to zero, so that the output signal of the transformer in the pulse form essentially represents a 1: 1 mapping of the input signal. With 10 μs long full periods of the primary voltage pulses z. B. Secondary voltage pulses with edge steepness of only about 100 ns (rise time) and 200 ns (fall time) can be achieved. The falsification in the time behavior can thus be reduced to values below 1% in the range from 25 kHz. The operating properties of the transformer are thus greatly improved, in particular the properties between idle and load operation no longer change significantly. They hardly change when the duty cycle changes.

The use of a short-circuitable according to the invention Auxiliary winding enables advantageous control of transistors in floating mode. Furthermore expedient is the use for floating transmission faster voltage increases.

In an advantageous embodiment of the invention Transformer is between the center bridge and the winding is a suitably tubular winding body made of insulating material and between the winding and an insulating body is arranged on the outer body. By means of this Insulating bodies prevent and prevent corona effects Insulation protection and a constant dielectric created. The winding body not only serves to hold the Winding, but also as a spacer to ensure adequate Ensure the distance of the winding from the center bar. This will make the transformer work easily reproducible.  

Insulating foils are advantageous between the windings arranged. This also ensures that the distance between secondary and primary winding if possible is small, which improves the coupling. Appropriately the foil-shaped insulation is wider than that Foil winding. Has been suitable for. B. a supernatant of about 1 mm. If the overhang is too low, it happens because of the significant charge shifts at the high Working frequencies (MHz) for rollovers and ionizations in the edge area, especially on sharp edges of the film etc., and there is a risk of e.g. B. Layer shorts. However, if the supernatant is too large, the effective one Coupling area disadvantageously small. For the material of the plastic insulation is advantageously used. The polyester material PETP has proven to be cheap proved to be a very small dielectric constant Has.

The use of the film winding according to the invention is particularly advantageous with higher current densities and a low number of turns. Due to the film surface, the coupling efficiency is significantly increased in relation to known transformers. Because of the large surface area, it is possible to work with a larger active conductor cross-section (skin effect) with current densities of 15 A / mm ² and more. That is, even though the cross section is smaller per se than with conventional windings, the effective cross section is larger. As a result of the larger active conductor mass, the conductor material is heated less strongly despite the higher current densities, since the heat can be dissipated better from the winding space. In addition, the dynamic internal resistance of the film winding is very small.

The lines of force of the magnetic field through, so that a large induction area is available. It also doesn't come anymore a divergence of the lines of force on HF strands and the like, rather, the lines of force of the Field through the wrapping film.

In conventional transformers with comparable output currents, the current densities have to be reduced to approximately 1.5 A / mm ² , which means an additional increase in weight and an increase in the winding space, so that a larger core type must be selected. In contrast, less winding material is required in the transformer according to the invention.

Less magnetic material is also required therefore the mass of the transformer according to the invention significantly reduced compared to conventional transformers, what a weight and material cost saving means.

The transformer according to the invention is suitable as a pure one Power pulse transmitters, in particular with clock frequencies between about 20 to 100 kHz, duty cycle 1: 1, namely for both current and voltage transformation. He reliably creates electrical isolation. Advantageous is its use to control power transistors in floating mode (switching regulator power supplies).

Another advantageous application of the invention Transformer in the design with externally short-circuitable  Winding is used as a fast energy pulse transmitter. This is due to the extremely low delay time between input / output signal at higher energies.

The transformer according to the invention is also advantageous usable for keying or pulse group transmission, if there is an extremely short pulse delay between Input and output signal arrives.

Another application of the transformer according to the invention is the feedback transformer. The transformer can be quickly switched off by external wiring, d. H. the feedback is interruptible. There is a sharp interruption through a short-circuitable winding between primary winding and secondary winding. The goodness of Transformers result from differentiation the primary voltage on the primary winding when short-circuited Auxiliary winding and high-resistance generator.

Further applications of the transformer according to the invention are z. B. power pulse transformer, current measuring transformer, Modulation transformer.

For the production of a transformer the secondary and primary windings are called cylinder windings wound on each other and always between a primary winding on the winding body a secondary  (partial) winding arranged. The windings are like this wound that a live primary winding each adjacent to a current-carrying secondary part winding is. It is advantageous between a primary winding and a secondary part winding is always arranged on the outer web, whereby the coupling efficiency is increased.

The manufacture of a transformer is advantageous between the respective primary and secondary winding a metal foil is arranged, the connections of which are led out and be connected to the protective conductor. Hereby is a short circuit current between the primary and Secondary winding prevented.

In one variant between adjacent current-carrying partial windings the primary and secondary winding one each one-layer winding, which can be short-circuited if possible, which allows controlled energy transfer to interrupt. Suitable wiring can be used the transmission characteristics of the transformer as well improve significantly.

The secondary (partial) windings will be executed as foil windings. Has proven to be useful proven, a winding film and an insulating film to wrap together. This version allows for one, a high degree of coupling between the windings to achieve by the winding surface and thus the coupling surface is increased, on the other hand the distance is the Windings reduced from each other. Therefore, it is also preferred for the insulation between the (partial) windings Insulating film used.  

A transformer with a primary and a secondary winding is made according to by winding a first secondary part winding and a first insulation is applied to this. Then the primary winding is wound up and with a second provided external insulation. Then one second secondary section winding and a third insulation applied and finally the winding arrangement on the Transformer core mounted. Alternatively, if from a division of the secondary winding is refrained from Secondary winding and then a first insulation on the Winding bodies are applied. Then the Primary winding wound up and with a second insulation provided, and finally the winding arrangement is on mounted on the transformer core. This second variant is particularly easy to manufacture and therefore useful if not so high demands on reducing the dead time t * can be provided.

An inventive transformer with two primary and two secondary windings is made by applying after the first secondary and primary winding and their Insulations on the winding body the second primary winding and on this a third insulation and the second Secondary winding and a fourth insulation applied will. Then the winding arrangement on the Transformer core mounted.

Should a transformer with two primary and two each Secondary part windings are produced, so at another variant the third secondary section winding on the third insulation and applied a fourth insulation, then the second Primary and fourth secondary section winding with one  fifth and sixth insulation applied and then the winding arrangement on the transformer core assembled. The current-carrying secondary part windings always wrap the current-carrying in this arrangement Primary winding.

The winding arrangement has proven to be cheap soak on the transformer core before assembly or to impregnate.

Further embodiments of the invention are the subclaims refer to. The invention is in several embodiments illustrated with the aid of the drawing. It demonstrate  

Fig. 1 is a diagram of different transformer core materials and -Herstellungstechniken illustrates schematically the transmission power depending on the frequency and the use in the various frequency ranges,

Fig. 2 shows a measuring arrangement for the determination of transmission characteristics of transformers with respect to the core design and the core material,

3 shows a measuring circuit. Used in experiments with the in Fig. 2 represented measuring arrangement

Fig. 4 shows the time course (a) of the primary voltage, (b) the primary current, and (c) the secondary voltage in the experimental measurements,

Fig. 5 shows the waveforms of the primary voltage according to Fig. 4 (a) in enlarged scale;

Fig. 6 is a vector diagram of the impedance of the magnetic material,

Fig. 7 is a vector diagram of the overall impedance of the core,

Fig. 8 is a vector diagram of the permeability of the magnetic material,

Fig. 9 is an equivalent circuit diagram of the transformer according to the invention,

Fig. 10 is a cross-sectional view through a first embodiment of the transformer according to the invention,

Fig. 11 is a circuit diagram of the transformer shown in Fig. 10,

Fig. 12 is a side view of a second embodiment of the transformer according to the invention,

Fig. 13 shows an enlarged detail of the longitudinally in Fig. 12 transformer shown in sectional view of line A in Fig. 12,

Fig. 14 is a circuit diagram of the transformer shown in Fig. 12,

FIG. 15a is a side view of a third embodiment of the transformer according to the invention,

Fig. 15b is a sectional view taken along line AB in Fig. 15a,

Fig. 16 shows an enlarged detail corresponding to lines C, C 'in Fig. 15b,

Fig. 17 is a circuit diagram of the transformer shown in Fig. 15,

Fig. 18 shows the time course (a) of the primary voltage, (b) the primary current, and (c) the secondary voltage in the inventive transformer,

Fig. 19 is a side view of a fourth embodiment of a transformer according to the invention with auxiliary winding,

Fig. 20 is a sectional view of a section A of a first variant of the transformer shown in Fig. 12,

Fig. 21 is a sectional view of a section A of a second variant of the transformer shown in Fig. 19,

Fig. 22 is a circuit diagram of the transformer shown in Fig. 19,

Fig. 23 is a measuring arrangement for determining the transmission characteristics of transformers with externally kurzschließbarer auxiliary winding,

Fig. 24 are timing charts for a circuit used in the measuring arrangement shown in Fig. 23 and

Fig. 25 (a) to (g) the temporal behavior of Primärspannungs- and secondary voltage pulses with and without external kurzschließbare winding.

A first exemplary embodiment of the invention is explained below with reference to FIGS. 10 and 11. The core 102 of the transformer is an EE core (EE 65 ), the outer webs 104, 104 ' and central web 106 are shown in half in longitudinal section. The core material is ferrite.

The winding arrangement 120 is arranged on the central web 106 . It comprises a winding body 122 made of a plastic material, on which a primary winding 124 and two secondary part windings 126 and 128 are wound. The winding arrangement is such that the secondary part windings 126, 128 surround the primary winding 124 . In the exemplary embodiment shown, all windings are foil windings. The foil used is a 25 μm thick and 40 mm wide copper foil. The connections of the windings are schematically designated E and A in FIG. 10. The number of turns is 22 (primary winding) and 32 (secondary windings).

Insulations 130, 132 and 134 are arranged between the windings and surrounding them. In the exemplary embodiment shown, they are made of PETP film. The film used is 0.2 mm thick and 44 mm wide. The protrusion of the film-shaped insulation with respect to the film winding is therefore about 2 mm.

The circuit diagram of the winding arrangement is shown in Fig. 11. The transformer shown is designed for a power of 4 kW. The primary voltage is 220 V DC, the secondary voltage on the secondary part windings is 320 V. The maximum primary and secondary current is 20 A. The winding voltage is therefore per 10 V per winding.

A second exemplary embodiment of the transformer according to the invention is illustrated in FIGS. 12, 13 and 14. FIG. 12 shows a side view of the transformer, the core 102 of which is again designed in the EE design and consists of ferrite. The outer webs 104, 104 ' and the central web 106 of the core comprise a winding chamber 108 . A winding body made of a plastic square tube, the inside diameter of which is approximately 0.5 mm larger than the outside diameter of the central web 106 of the core 102 , is formed without side walls and surrounds the central web. The two primary windings 124 and 138 and two secondary part windings 126, 128 and 136, 140 are wound onto the center body. The primary windings 124, 138 are made of stranded copper wire (CuL wire). The secondary part windings of the primary and secondary windings are such that a secondary part winding 126 or 136 lies between the associated primary winding 124 or 138 and the winding body 122 .

An insulation is arranged between the windings, which is a plastic film, which preferably consists of PETP. The width of the insulating foil is approximately 1 mm less than the length of the central web 106 of the core 102 , and it is approximately 2 mm larger than the width of the copper foil.

The winding arrangement is illustrated in an enlarged detail shown in FIG. 13, which represents a sectional view along line A in FIG. 12. Fig. 14 shows the circuit diagram of the windings.

The transformer is manufactured as follows: First, a first secondary part winding 126 is applied to the winding body 122 , then an insulation 130 . A first primary winding 124 is then wound on this insulation using CuL winding technology, and insulation 132 is in turn applied thereon. A second secondary part winding 128 is then wound up, which, like the first secondary part winding, is a winding film. An insulation 134 is then arranged thereon. Accordingly, a third secondary part winding 136 , a fourth insulation 142 , a second primary winding 138 , a fifth insulation 144 , a fourth secondary winding 140 and a sixth insulation 146 are applied. The beginning of the winding of the individual windings is marked and the conductor foil is provided with copper strands. The conductor film and the insulating film are advantageously wound from one another at the same time to insulate the individual film turns. The finished wound bobbin is then mounted on the core 102 . Then a mounting bracket for the core is attached.

The transformer described above is simple and inexpensive producible. It is for a temperature range between -40 ° C and + 120 ° C applicable. Its dielectric strength is 4 kV DC in the exemplary embodiment shown. The  Transformer works very reliably and offers that Advantage of minimal delay times in the pulse transmission. It is particularly suitable for floating power Impulse transmission, e.g. B. with a duty cycle of 1: 1, suitable.

The transformer of the third exemplary embodiment has a winding arrangement comprising two primary windings 124, 138 and two secondary windings 148, 150 . Fig. 15a shows a side view of the transformer, and Fig. 15b shows the transformer in cross section. As far as the transformer is the same as the transformer of the second exemplary embodiment above, a detailed description is omitted in order to avoid repetitions. The same parts are labeled with the same reference numerals. The winding of the transformer differs from the previous exemplary embodiment. The two primary windings are separated from one another by insulation 152 . They are each surrounded on the other side by an associated secondary winding 148 or 150 , which is shielded from the core in order to favor the winding coupling. The winding arrangement is illustrated in an enlarged detail from FIG. 15b in the area of lines C, C 'in FIG. 16.

Fig. 17 shows the circuit diagram of the coil assembly.

The transformer of the third embodiment is manufactured as follows:

The secondary winding 148 consisting of winding film is wound onto the winding body 122 and then an insulation 130 is applied. The primary winding 124 , subsequently an insulation 152, is applied to it. This is followed by the second primary winding 138 , a further insulation 144 , the second film-shaped secondary winding 150 and an outer insulation 146 . The winding arrangement is then placed on the core as in the previous embodiment.

This transformer is inexpensive and easy to manufacture and works with high reliability in the temperature range between -40 ° C and + 120 ° C. Its dielectric strength is 4 kV DC. Because of the winding arrangement is the capacitive coupling between the primary and secondary windings low. Power impulses with high Edge steepness and short delay times with variable Duty cycle are transmitted.

The time behavior of primary voltage, primary current and secondary voltage shown in FIGS. 18 a to c illustrates the advantages of the transformer according to the invention, which are essentially due to the spatial arrangement of the windings with respect to one another. The pulse duration is essentially equal to the respective half-period of the primary voltage. The small time offset, ie the time delay t 'of the signal or pulse increases is based on the switching times of the transistors used in the circuit. Since the pulse roof is essentially horizontal, the performance of the circuit components can be exploited very well. The residual roof slope of the primary current signal is based on the magnetizing reactive current.

In Figs. 19 to 22 a fourth embodiment of the transformer according to the invention is shown which is provided with an auxiliary winding. FIG. 19 shows a side view of the transformer, similar to FIG. 12. The same parts are denoted by the same reference symbols and will not be described again.

FIG. 20 shows a sectional view of the enlarged section of a first variant of the winding arrangement shown in FIG. 19.

A first secondary part winding 158 (with intermediate insulation 166 ) is wound on a winding body 122 surrounding a core 102, and is designed as a film winding. The secondary part winding 158 is surrounded by insulation 168 . The primary winding 154, 156 is designed as a wire winding and does not extend over the entire winding width. In addition to the primary winding, ie its two partial windings, an auxiliary winding 162, 164 is wound. The two windings are provided with intermediate insulation 172 and surrounded by insulation 174 , and an associated outer secondary part winding 160 with intermediate insulation 180 and outer insulation 182 is wound together on the two windings.

FIG. 21 shows a sectional view of the enlarged section of a second variant of the winding arrangement shown in FIG. 19. A first primary part winding 158 (with intermediate insulation 166 ) and an insulation 168 are wound onto a winding body 122 surrounding a core 102 . The secondary section winding and the insulation are film-shaped. A first auxiliary winding part 162 is wound on the arrangement and is surrounded by insulation 176 . Above is the primary winding 154, 156 , which is designed here as a wire winding, but can also be a foil winding. The primary winding is enclosed by insulation 174 , and a second auxiliary part winding 164 with insulation 178 is arranged above it, on which in turn a second secondary part winding 160 with intermediate insulation 180 and outer insulation 182 is wound.

Fig. 22 shows the circuit diagram of the coil assembly.

In Fig. 23 a measuring arrangement for determining the transmission properties of transformers with an externally short-circuitable auxiliary winding is shown, which are, for. B. can be the transformers shown in FIGS. 20 and 21. A generator 50 with a blocking capacitor 52 , which is fed with an input voltage U _E , comprises an oscillator 54 , ie a pulse width modulator. Primary part windings 40 a, 40 b of a transformer to be examined can be gently controlled by the oscillator 54 via two diodes 56, 58 and two switches S 1 and S 2 . Two secondary part windings 42, 44 of the transformer are shown, the wiring of the secondary part windings being merely indicated. An auxiliary winding 46 , the externally short-circuitable winding, is arranged between the primary and secondary part windings. The winding ends are connected via diodes 60 , the auxiliary winding 46 being switchable by a switch S 3 , which is preferably designed as a transistor. A decoding element 66 is connected via diodes 62 and 64 connected in parallel with the diodes 56 and 58 . An amplification, that is to say power, part is connected to the decoding element 66 and is in turn connected to the switch S 3 .

Fig. 24 shows timing diagrams of the switches S 1, S 2 and S 3. This illustrates that the switch S 3 is actuated whenever the other two switches are not actuated, ie when the primary voltage is zero.

The measuring arrangement shown in Fig. 23 operates as follows. The level "0" of the primary voltage, ie the generator voltage, is evaluated and used to control the switch S 3 . The auxiliary winding 46 is short-circuited by means of the fast circuit breaker S 3 and clamping of the winding during pauses in the primary voltage signal. The drive signal is amplified by the amplifier 68 . The output voltage of the auxiliary winding is rectified via diodes 60 .

The temporal relationships of the individual voltages are illustrated in FIGS. 25 (a) to (g). Fig. 25 (a) and (b) show the voltage waveform to the primary part windings 40 a and 40 b of the actuator according to the switch S 1 and S 2. Fig. 25 (c) shows the theoretical, desired secondary voltage. Fig. 25 (d) shows the no auxiliary winding in an active load having a nonlinear current rise (base-emitter path of a power transistor) practically achieved secondary voltage. This skewed load creates an asymmetrical voltage curve of the secondary voltage with respect to the zero axis, which was not shown to facilitate understanding. This course of the curve is thus achieved when the switch S 3 is not actuated and the auxiliary winding is free.

As the timing diagram illustrates, the secondary voltage is not zero if the primary voltage is the Value has zero, but rather has a value that is significantly greater than zero. The hatched areas illustrate the deviations in the signal curve between the primary and the secondary voltage to the one Corruption of the signals can be attributed.

Fig. 25 (e) illustrates the profile of the secondary voltage signals practically achieved with activated auxiliary winding. The course essentially corresponds to the desired course of the secondary voltage pulses. Values of the secondary voltage that deviate from zero do not have a further disruptive effect on the further signal processing, but can still be reduced. This time diagram, like all other time diagrams, is based on the load on the transformer with a predominantly active component (non-linear current voltage characteristic). In FIG. 25 (f), the secondary voltage pulses are out of phase by 180 ° in accordance with the profile shown in FIG. 21 (e), but for push-pull control. Fig. 25 (g) shows another timing diagram in which the positive pulses of the two secondary windings are shown and z. B. can be used to control transistors with a positive base current.

Investigations have shown that the internal resistance of the generator 50 has no influence on the behavior of the novel transmission system formed by the transformer with auxiliary winding.

Claims (8)

1. Power transformer in jacket design, with a core ( 102 ) made of ferromagnetic material and with at least one primary and one secondary winding, ( 124; 138; 154, 156 and 126, 128; 136, 140; 148, 150, 158, 160 ), at least one of which is a foil winding and which, as cylindrical windings with insulating layers ( 130, 132, 134, 142, 144, 146, 152, 168, 178 ) in between, concentric with one on the central web ( 106 ) of the core ( 102 ) applied winding body ( 122 ) are applied, the winding closest to the outer web of the core ( 102 ) being a secondary winding, characterized in that the secondary winding ( 126, 128; 136, 140.) in the transformer, which can be operated in particular for frequencies between 20 kHz and 100 kHz ; 148, 150, 158, 160 ) in foil construction with partial windings, closely coupled to the primary winding ( 124; 138; 154, 156 ), arranged spatially close to it and in the area of its highest force flow lines is located, the winding closest to the central web ( 106 ) being a secondary part winding ( 126, 148, 158 ) and between an outer secondary part winding ( 128, 140, 150, 160 ) and the outer web ( 104, 104 ′ ) of the core ( 102 ) an insulating body ( 134, 164 ) is arranged so that the extent of the energy transfer via the windings is increased by this spatial assignment. 2. Transformer according to claim 1, characterized in that between primary and secondary windings a single-layer insulated on both sides Metal foil with lead out and with a protective conductor connected connection is provided. 3. Transformer according to one of the preceding claims, characterized in that a single-layer externally short-circuitable winding ( 162, 164 ) is arranged between adjacent current-carrying partial windings of the primary and secondary windings. 4. Transformer according to one of the preceding claims, characterized in that the winding distance from the central web ( 106 ) of the core ( 102 ) is approximately equal to the winding distance from the outer web ( 104, 104 ' ) of the core. 5. Transformer according to one of the preceding claims, characterized in that an air gap is present between the winding body ( 122 ) and the central web ( 106 ) and between the insulating body ( 134, 146 ) and the outer web ( 104, 104 ' ). 6. Transformer according to one of the preceding claims, characterized in that it has the at least two superimposed winding arrangements each of two secondary windings ( 126, 128; 136, 140 ) and an intermediate primary winding ( 124, 138 ). 7. Transformer according to one of the preceding claims, characterized in that it has at least two primary part windings ( 124, 138, 154, 156 ) lying between the inner and outer secondary part windings. 8. Transformer according to one of the preceding claims, characterized in that the core ( 102 ) is of the winding core type.