Modular Transformer

Disclosure of invention

The invention refers to the transformers, which convert voltage of the electric current leaving invariable its wave form and do not contain intermediate DC circuit.

All the mentioned functions can perform an electric circuit (patent LV 12933), transformer according to the patent application GB 1261838 A, transformers with intermediate DC circuit, disclosed in US 7050311B2, and transformers disclosed in US 4678986 (prototype). The transformer module prototype contains only primary windings of the transformer and corresponding cores made of magnetic material, but the secondary winding is common for all the modules, that is wraparound with the same wire all cores, which find themselves in the magnetic field of the winding. For this reason the magnetic flows of the modules are conjugated between them and interferes one another. Such configuration hampers heat dissipation from the modules because of air influx lack to each module. In addition it does not allow making effective high-voltage insulation between primary and secondary windings.

The main drawback of the mentioned analogues and the prototype are:

- the transformer power is limited by the cooling performance capabilities and maximal voltage - by breakdown voltage of the proposed crosspoints solution;

- the framework does not ensure sufficient insulation in case of surge overloads (for example, lightning discharge), which in power distribution transformers can run up to 120 kV and even more;

- detached power supply to each consumer is not possible, because all the consumers are fed in parallel from the same outlet of the transformer;

- it is not possible to adjust the transformer output voltage according to the power transmission line length.

The analogous solution according to US 7050311B2 contains a rectifier, which absorbs voltage, thus increasing energy loss of the transformer. The device according to GB 1261838 A can operate only with low voltage because based on the push-pull converter.

The main scope of the invention is to make a transformer free of mentioned drawbacks, able to convert the voltage value leaving invariable its wave form, and easily configurable for power transforming according to the consumer request. The proposed invention offer to eliminate the mentioned complaints making the transformer of several separated modules that is of small transformers, which power is limited by the cooling capabilities of natural ventilation and each module operating voltage and current strength meets the crosspoints performance capabilities. The modules used in the invention, as opposed to the prototype, are full-value transformers, that is, each module contains as primary, as secondary windings with independent mutually uncoupled magnetic flows.

Description of attached figures

The essence of the invention is explained in the following figures, where: • Fig. 1 presents an alternative of the modular transformer arrangement;

• Fig. 2 presents an alternative of the three phase modular transformer circuit with star connection;

• Fig. 3 presents embodiment of the section S of modular transformer;

• Fig. 4 presents an alternative of the modular transformer section wiring according to the invention;

• Fig. 5 presents an alternative of the proposed modular transformer circuit with use of alternating current transistors;

• Fig. 6 presents an alternative of the proposed modular transformer circuit with MOSFET transistors.

An alternative structure of the modular transformer body KO, where the section S with modules M is disposed, is shown in the Fig. 1. The section S is connected to the high- voltage buses K3, which in their turn are connected to the high- voltage distributing board Kl, and to the low- voltage buses K4, which are connected to the low- voltage distributing board K2.

An alternative of the three phase modular transformer circuit with Y-connection where the transformer consists of three sections Sl, S2 and S3 is shown in the Fig. 2. Each section is

an independent magnetically non coupled transformer. The high-voltage cables connected to the terminals A, B, C and neutral the Nl. The low- voltage cables connected to the terminals X, Y, Z and the neutral N2. The high and low voltage circuits are separated by the insulating plate SO. There is 20 kV voltage between phase wires A, B and C, and 11.6 kV - between any phase wire and neutral Nl on the high- voltage side, and 400 V voltage between phase wires X, Y and Z and 230 V between any phase and neutral N2 on the low- voltage side.

An alternative of the modular transformer section S, where on the insulating plate SO 50 modules from MOl to M50 are arranged is shown in the Fig. 3. The insulating plate SO is outfitted with contact fixing devices to provide connection with high- voltage Tl and low- voltage T2 buses.

An alternative of the wiring diagram of modular transformer section, consisting of 50 modules from MOl to M50 is shown in the Fig. 4. Each transformer's module is an independent magnetically non coupled transformer. The primary windings of the modules are connected in series and secondary in parallel. For all the modules the insulating plate Sl separates the primary and secondary windings. The switches SWI l, SWl 2, and SW22 serve for the transformer output voltage adjustment. The switches SWI l, SW12 allow connecting the neutral Nl to the module MOl or to the module M02. Connection of the neutral Nl to the module M02 raises the voltage drop on the modules and, thus, also the output voltage increases. To avoid excitation current losses in the module MOl it is disconnected from the low- voltage terminal by means of the switch SW22.

An alternative of the modular transformer module wiring diagram with alternating current (AC) transistors XI l, X12 and X21, X22 is shown in the Fig. 5. The input and output circuits are separated by the insulating plate Sl. The AC transistors XI l, Xl 2 and the capacitors CI l, C12 form half-bridge modulator. The AC transistors X21, X22 and the capacitors C21, C22 form the half-bridge demodulator. The synchronising generator XlO, which output is connected to the primary winding ST_L1 of the synchronising transformer, assures modulator and demodulator synchronisation. The secondary windings ST_L11, ST_L12, ST_L21 and STJL22 of the synchronising transformer assure synchronous switching of the AC transistors XI l, X12, X21 and X22. The current transformer AT,

which primary windings AT Ll and AT L2 are series connected with half-bridge capacitors CI l and C 12 and secondary windings from AT Ll 1 to AT L 14 are connected to the corresponding AC transistors injectors. Voltage transformer VTl, which windings VT Ll and VTJL2 are inserted correspondingly in the modulator and demodulator half- bridge diagonals, serves for energy transfer from the primary to the secondary side. The voltage to be transformed is connected to the terminals TI l, Tl 2 and the transformed voltage is taken off the terminals T21, T22. The input and output circuits are separated by the insulating plate S 1.

An alternative of the modular transformer module wiring diagram with MOSFET transistors connected in series, which by pairs M1M2, M3M4, M5M7 and M6M8 form AC switches, is shown in the Fig. 6. The input and output circuits are separated by the insulating plate SO. The AC switches M1M2, M3M4 with capacitors CI l and C12 form half-bridge modulator. The AC switches M5M7 and M6M8 with capacitors C21 and C22 form half-bridge demodulator. The synchronising generator XO, which output connected to the primary winding VS LO of the synchronising transformer VS, assures synchronisation of the modulator and demodulator. The secondary windings VS_L11, VS L 12, VS L21 and VSJL22 of the synchronising transformer assure synchronous actions of the AC switches. Voltage transformer VTl, which windings VT Ll and VT L2 are inserted correspondingly in the modulator and demodulator half-bridge diagonals, serves for energy transfer from the primary to the secondary side. The voltage to be transformed is connected to the terminals Tl 1, T12 and the transformed voltage is taken off from the terminals T21, T22.

Interpretation of the invention scope in function of concept of the modular transformer application

It is proposed to assure the necessary power and other transformer parameters making modular transformer by combining, according to the consumer demand, several modules in blocks and several blocks in sections, where each section consists at least of one block, at that in multiphase, for example, in three phase transformer configuration, each phase is connected at least to one section. To obtain the transformer with desired parameters, sections, modules and blocks should be connected in corresponding combination, including

star, delta and/or zigzag connection. The necessary operating voltage of the block can be reached by connecting modules inputs and/or outputs in series. To assure the necessary operating current strength from the block, the modules input and/or output can be connected in parallel. To obtain the necessary operating voltage from the section, blocks inputs and/or outputs can be connected in series. To assure the necessary operating current strength from the section the blocs input and/or output can be connected in parallel. The insulating plate made of "Duroid" type material or other appropriate material, placed between the module input and output circuits, including corresponding windings, assure necessary insulation of the mentioned module inputs and outputs.

To assure effective energy transfer from the modular transformer input to the output, it is proposed to make in the mentioned insulating plate openings for placing energy transferring elements, for example, cores made of ferrite or other magnetic material, if the transfer occurs by magnetic field, or piezoelectric crystals, if the transfer occurs by acoustic vibrations. To prevent the transformer breakdown through the openings in the insulating plate the gaps between primary and secondary sides of the plate to be filled with elastic insulating compound, for example, the compound made on the base of barium titanate or with admixture of the MnZn ferrite, which permittivity constant is much greater, then the permittivity constant of the insulating plate.

To reduce the transformer manufacturing costs and facilitate its assembling it is proposed to make winding as printed circuit board, which consists of one or several layers made of conducting material, for example, copper, separated by insulating interlayer.

To reduce leakage inductance and enhance the transformer cooling it is proposed to use for energy transfer from the transformer input to its output planar or other appropriately shaped cores of magnetic material, for example, ferrite.

To reduce the transformer weight and outer dimensions, the mentioned modules can be made with intermediate high-frequency circuit, that is, first, common AC input voltage by means of modulator is transformed into high-frequency voltage, then occur voltage transformation, and, finally, by use of the demodulator the initial voltage frequency is restored to the common value. It is possible to use as modulator and demodulator

synchronously operating foil bridge or half-bridge, or other commutating devices. Voltage conversion can be done by circuits based on active elements, operating with alternating current, for example AC transistors, MOSFET transistors, IGBT and other. So, it is not necessary to include an intermediate direct current circuit and it is possible to reduce the transformer losses.

For the purpose to simplify the variation of the transformer power, leaving unaltered the component design, each transformer phase is connected with at least one section, which form one phase transformer, composed of modules. The minimal section number is equal to the transformer phase number. As an example of such configuration it is possible to mention three phase transformer with nominal input voltage between phases 20 kV. Voltage against neutral is 1.73 times less, that is, 11.5 kV. Each phase is connected to one section, consisting of two blocks connected in series, each with 25 modules. Then the voltage drop on each module is 230V. But if the input voltage will be 10 kV, then the voltage drop on each of the 50 modules also reduce up to 115 V. It means that the block outputs should be connected in series to get 230 V. To step up the transformer power it is enough to attach the necessary number or sections. One or more sections can be disposed on the mentioned insulating plate. The modules, belonging to each block can be mounted on the insulating plate like prefabricated parts with their own outputs or like module components.

The transformer section, consisting of 50 modules on the insulating plate 6, forms square matrix 5x10 (Fig. 1 and Fig. 3). The both sides of the insulating plate are covered with printed circuit boards (PCB), which right sides are used to form the high-voltage circuits and thus the modules outputs are connected in series. The inside of the plate is used for low-voltage circuits, thus the modules outputs are connected in parallel. Wire width on the low-voltage side depends on the number of connected modules, because the current strength grows in proportion with number of modules. The widest wires are near the output. The input/output contacts Tl and T2 on the printed circuit board correspond respectively to the high- voltage K3 and low- voltage K4 outputs (Fig. 1). It means that the section plate has altogether four contacts for high-voltage connection: three for phase connecting and one - for neutral. On each section plate two lines of contacts are switched off, leaving only the contact which corresponds to the given section phase. Contacts for

connection to the low-voltage buses are arranged on the section plate in the same way. It should be noted, that the shape of the section plate SO (Fig. 3) corresponds the transformer shell profile, but the contact "teeth" match with the pocket in the shell, with the buses for connection to the input/output leads of the section plate.

To use the proposed modular transformer in the power distribution network, when the distance from the transformer to the consumer can be so long, that voltage drop on the electric line notably influences on the voltage value, which is received by the consumer, the invention provides possibility of right adjustment of the transformer secondary voltage, so assuring the transformer use also for stable high- voltage supply, for example of X-ray equipment, electron accelerators and so on.

With the scope to assure the supply of nominal voltage to each consumer regardless of the distance and other circumstances, each mentioned section is provided with jumpers, allowing connecting or disconnecting to the section some modules and/or their combination. For example, if the section contains 50 modules, then 1 module disconnection cause the output voltage step up by 2%. Disconnection of 5 modules steps up the output voltage by 10%, but adding the 5 module section decreases the output voltage by 9%. If it is necessary to assure the stable voltage on the load the relays of any type, including semiconductor relays, should be used on the contact to commutate the alternate current. The mentioned relays are commanded by special devise in function of the voltage and applied load.

With the scope to protect the modular transformer against hostility of the ambient, such as humidity, mould formation and others, each mentioned module and/or section can be covered by protective layer, for example, insulating lacquer, compound or polymer layer.

To reduce the manufacturing costs and weight, the proposed construction can be created without use of expensive and heavy high- voltage insolators, but the transformer shell is made of insulating material with embedded metal, for example copper, buses for mentioned sections and the transformer output terminals connection. The mentioned buses are provided with fixtures useful for all types of connections, for example threaded holes,

screws or other type of fixing elements. To assure sufficient strength against external mechanical impacts the transformer shell walls can be stiffened with appropriate reinforcement, for example glass, carbon or other fibers. Outside of the shell can be covered with protective layer (or such layer can be integrated with the shell material in manufacturing process), which reflect UV and/or IR, for example, varnish or special pigment layer.

The proposed modular high-power transformer on the base of previously disclosed information in the invention is structured in 15 Claims with emphasise on the Claim 1 that, separate magnetically uncoupled transformers are used as modules, having so low-power, that their cooling can occur by natural ventilation, at that to step up voltage the mentioned modules windings are connected in series and/or to step up the current strength the mentioned modules windings are connected in parallel, besides for voltage conversion such active elements are used, which can operate with alternate current, and as a result the proposed modular transformer does not contain intermediate direct current circuit.

The list of the adjective technical features, included in the claims, is expressly or by implication derived form previously disclosed information and attached depictions:

- the voltage protection device, for example, one or more varistors, is connected in parallel to each module inputs and outputs, besides the mentioned device can be integrated in the module or connected to the module from outside;

- the mentioned modules are provided with modulator and demodulator, which assure double frequency conversion, that is, first, the power supply frequency is raised, then voltage is transformed and after the initial power supply frequency is restored; - the transformer is divided into the sections according the number of alternate current phases;

- each phase is connected to two or more sections, which between them form parallel, delta, star and/or zigzag connections;

- the mentioned sections are divided in two or more blocks, consisting of mentioned modules, at that the mentioned blocks windings form between them series, parallel, delta, star and/or zigzag connections;

- only inputs of the mentioned sections are connected in parallel, but section outputs are connected each to another consumer;

- the mentioned sections are disposed in the shell, made of insulating material, with metal buses, provided with contact fastening elements for mentioned sections and outer leads connection, embedded in the shell walls;

- the mentioned sections are assembled on sufficiently thick insulating plate, at that the mentioned modules medium-voltage windings are disposed on one and low-voltage windings on the other side of the mentioned plate, besides the medium-voltage and low- voltage windings are coupled by means of magnetic material, for example, ferrite, core, and in addition the mentioned windings made of insulated wire winding and/or also as one or multi layer printed circuit board; - the mentioned optionally shaped cores, including planar cores, are disposed in the mentioned plate openings so, that the mentioned wirings wrap them and the gaps between mentioned plate openings and mentioned cores are filled with elastic insulating mass, which permittivity constant is much greater, then the mentioned insulating plate permittivity, for example, polymer with admix of barium titanate or Mn Zn ferrite; - the electronic elements, able to commutate alternate current, for example, AC transistors, are used in the mentioned modules to convert frequency, besides those elements are made with protective cover or also as casing-free and mounted directly on the mentioned plates;

- the mentioned frequency converters in each mentioned module run with one o more commutation cycles and are mutually synchronized, at that the synchronization is assured by synchronizing transformer, which primary winding/s connected to the pulse generator output and secondary one connected to the driving input of the mentioned commutation elements, at that the mentioned synchronizing transformer windings disposed on the side of the mentioned plate together with corresponding commutation element and coupled between them by magnetic, for example, ferrite conductor, which cores are placed in the mentioned plate openings in such a way, that mentioned windings wrap them, at that they can be optionally shaped, including planar shape;

- synchronising occurs by means of optical signal generators, for example, optrons, which are made also of discrete elements and disposed in such a way, that emitter, for example, LED, placed on one side of the mentioned plate and receiver, for example, photodiode, - on the other side of the same plate, at that the mentioned plate is made of optically transparent material or there is a window of transparent insulating material in the plate where the optron is installed;

- energy transfer from one to another side of the mentioned insulating plate occurs by means of piezoelectric transformers;

- the mentioned sections provided with embedded commutating elements, which allow to switch off a part of the mentioned modules or add to the mentioned section additional modules, at that the mentioned commutating elements can be relay of any type, including solid-state relay, controlled by electronic pilot block in function of voltage and load.