Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
VOLTAGE STABILISER WITH VARIABLE SHIELD
Document Type and Number:
WIPO Patent Application WO/2019/087219
Kind Code:
A1
Abstract:
A voltage stabiliser (1) is disclosed, comprising two fixed windings (4, 5) and a mobile and in short-circuit one (6), such as a voltage regulator. Within each of the two fixed windings (4, 5) another winding (7, 8) is introduced, said two other windings (7, 8) being fixed and electromagnetically coupled to the first two ones. Generally, said mobile winding is moved axially with respect to said fixed windings (4, 5; 7, 8) by a motor (3), through a worm screw.

More Like This:
Inventors:
CASTOLDI, Alberto (Via Vittor Pisani 28, Milano, 20124, IT)
Application Number:
IT2017/000243
Publication Date:
May 09, 2019
Filing Date:
November 06, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
CASTOLDI & MORETTI S.R.L. (Via Vittor Pisani 28, Milano, 20124, IT)
International Classes:
G05F1/247; G05F1/253; H01F29/08
Foreign References:
GB652558A1951-04-25
US2274015A1942-02-24
GB514972A1939-11-22
Other References:
PALUEV K K: "Power Transformers With Concentric Windings", TRANSACTIONS OF THE AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS, AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS, NEW YORK, NY, US, vol. 55, no. 6, 1 June 1936 (1936-06-01), pages 649 - 659, XP011349398, ISSN: 0096-3860, DOI: 10.1109/T-AIEE.1936.5057329
Attorney, Agent or Firm:
VATTI, Francesco et al. (Via S. Agnese 12, Milano, 20123, IT)
Download PDF:
Claims:
CLAIMS

1) Voltage stabiliser (1), comprising two fixed windings (4, 5) and a sliding and short-circuited winding (6) , characterised in that within each of the two fixed windings (4, 5), another winding (7, 8) is introduced, wrapped around the same core, said two other windings (7, 8) being fixed and electromag- netically coupled to the first two ones.

2) Voltage stabiliser (1) as claimed in claim 1), characterised in that said sliding winding (6) is moved axially with respect to said fixed windings (4, 5; 7, 8) by a motor (3) .

3) Voltage stabiliser (1) as claimed in claim 2), characterised in that the motor (3) is a brushless motor.

4) Voltage stabiliser (1) as claimed in any one of claims 2) or 3) , characterised in that the motor (3) moves a worm screw that operates the translation of the winding (6) in an axial direction.

5) Voltage stabiliser (1) as claimed in any one of claims 2) to 4) , characterised in that the motor (3) is activated by a feedback electronic scale with the voltage (V2) that is to be stabilised.

6) Voltage stabiliser (1) as claimed in any one of claims 2) to 5) , characterised in that the motor (3) has a speed reducer .

Description:
VOLTAGE STABILISER WITH VARIABLE SHIELD

DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to a voltage stabiliser, to be used in electrical circuits to eliminate, or at least to alleviate, sudden changes in voltage of equipment power supply. BACKGROUND OF THE INVENTION

Since the invention of the bulb (1879) , electrical equipment has spread enormously. There are electrical appliances both for domestic use (appliances, lighting, computers) , for industrial use and for medical use.

The spread of electrical equipment has caused the power netword to expand continuously, to reach virtually all inhabited areas, at least in the industrialised world: while there are housings, such as Alpine cottages, that are still not connected to the power network, they however embody exceptions, which are less and less easy to find.

In fact, the extension of the power network is one of the main causes of the spread of a good quality of life in industrial civilisation.

Over time, electrical equipment, besides spreading and increasing by number and models, also increased their versatility, their precision of use, and the fine operation, bringing enormous benefits with them. Examples of this include electromedical equipment (often allowing to save human lives) , computers, laser cutting equipment and others.

However, in addition to these advantages, the most sophisticated equipment presents the drawback of being more sensitive to external disturbances. Among these disturbances, one of the most common and problematic is the oscillation of network voltage. Among the drawbacks associated with network voltage oscillations the loss of data, the creation of defects in the products being manufactured, machinery operation breakdown, reduction of service life of industrial assets, security loss and others could be found.

Normally, those who manage the power distribution networks guarantee a maximum oscillation of ± 10% compared to the nominal value. In Europe, this nominal value is 400 V as concatenated and 230 V as the phase-to-neutral difference, normally with a frequency of 50 Hz.

Usually, electrical equipment manufacturers guarantee a smooth operation throughout the guaranteed voltage range, so that if there are not oscillations higher than the ones insured as maximum, the equipment should not have any problems. However, reality is not always that bright. In some cases, indeed, for several reasons (especially in the event of particularly fragile and sensitive equipment) the tolerance is narrower and the normal maximum voltage oscillations are too high for them to smoothly operate. In other circumstances, in spite of the statements of the operators, oscillations exceed the maximal values guaranteed. For example, this happens often during meteorological events such as thunderstorms. If the distribution networks are particularly long, for example, the voltage tends to be very low, resulting in less than 400 V - 10%. The length has rather an impact on the impedance, so that the voltage is greatly reduced. Another reason for lowering the network voltage relates the fact that, when switched on, many devices lead to a power absorption of up to 6 times higher than the one resulting during normal operation, thus leading to a major voltage reduction.

If, in the event of re-phasing, a load that should be disconnected is kept connected, an undesirable voltage increase may occur. Another cause of sudden voltage increases is related to the detachment of high-absorption equipment. Voltage drops are more frequent where there is a lack of a capillary electrical power distribution.

It should also be noted that the increasingly massive use of energy sources, such as solar and wind energy - which are by themselves changeable because of the variability of atmospheric conditions on which they depend - results in an increase in voltage variability, also because of their fragmentary arrangement on the territory.

Also the increase in the number of equipment, linked to in- dustrialisation, causes the networks to be insufficient to maintain the desired voltage; a balancing is usually obtained only after quite a long time.

For these reasons, the importance to provide and install voltage stabilisers upstream of the equipment has been increasingly growing. A voltage stabiliser is a device that receives variable-voltage electrical energy and transforms it into fixed- voltage electrical energy, compensating in real time for all the variations that are created in the network. Such deviations must be compensated for as long as they are present, a time that is not predictable, at least not in an exact manner.

To be useful, a stabiliser must be able to work under load, i.e. without the need of opening the circuit.

There are several types of voltage stabilisers on the market nowadays .

There are stabilisers with discrete voltage regulation. They mostly consist of transformers or auto-transformers, to which a particular on-load switch has been applied. This on-load switch is very fragile and expensive and is generally used with oil-immersed large equipment. In practice, the voltage adjustment and its adaptation to the instantaneous situation occurs by passing a mobile contact on fixed contacts. Such fixed contacts each correspond to a predetermined voltage value; in practice, the mobile contact, passing from a fixed contact to another leads the value of the output voltage from a value to the next one. For this reason, the compensation of voltage oscillations occurs in a "stepped" manner, i.e. discreetly, as illustrated in fig. 8.

To ensure a minimum of continuity, adequate power resistors to smooth the voltage jump can be inserted.

This type of stabiliser has some drawbacks, which are still unresolved. Firstly, the fact that the compensation takes place in a stepped manner means that the value on which the stabiliser will remain from time to time will be, except in particular cases, which are rare and very lucky, different from the one actually sought, even if the deviation will not be remarkable (a few percentage points, anyway). In addition, as far as various measures have been taken to reduce the risk, moving the mobile contact on fixed contacts causes the development of electric shocks (sparks) in any case, which could provoke danger and shorten the life of the components. Lastly, it is noted that due to the high costs of these switches, their use in stabilisers or in stabilised transformers smaller than 4000 kVA is uneconomic.

Beside these stabilisers, there are continuous ones. They exploit the passage of a contact, made as a wheel or a slide, onto a winding. This movement allows to partially split the number of active winding turns, using only some of them for each time. In this way, the voltage value is varied, depending on the number of turns that remain active after the movement.

Although it is a brilliant solution itself, also this stabiliser exhibits some drawbacks that are not yet resolved in a satisfactory way. Even in this case, indeed, the contact between the two parts causes electrical shocks, which are dangerous and a source of wear for the windings. Because of this, the maintenance operations required by these stabilisers are rather frequent, mainly affecting their use. For this reason, this type of stabiliser can only be used for rather low voltages, so that the slide can pass through and avoid excessive electrical shocks.

In the past, it was also attempted to create a stabiliser with a variable induction voltage regulator, providing the movement of the rotor of an electric motor relative to the stator, but this solution proved to be totally unworkable and is now completely in disuse.

SUMMARY OF THE INVENTION

The underlying problem of the invention is to propose a voltage stabiliser structure able to overcome the mentioned drawbacks and to allow to maintain a stable voltage, possibly with continuous voltage compensation and without creating risks and damages caused by sparking creation. This object is achieved by a voltage stabiliser, comprising two fixed windings and a sliding and short-circuited one, characterised in that within each of the two fixed windings, wrapped around the same core, another winding is introduced, said two other windings being fixed and electromagnetically coupled to the first two ones. The dependent claims disclose preferred features of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will anyhow be more apparent from the following detailed description of a preferred embodiment, given by mere way of non-limiting example and illustrated in the accompanying drawings, wherein:

fig. 1 is a side view, partially in section, of an embodiment of the stabiliser according to the present invention;

fig. 2 is a sectional side view of the stabiliser according to an embodiment according to the present invention;

fig. 3 is a plan view of the stabiliser of fig. 2;

fig. 4 is a general diagram of the stabiliser according to the present invention;

fig. 5 is a diagram of operation of the stabiliser according to the present invention;

fig. 6 is a block diagram illustrating the operation of the stabiliser according to the present invention;

fig. 7 is a diagram similar to fig. 4, but illustrating a voltage regulator;

fig. 8 is a diagram of the voltage change in a stabiliser according to the prior art; and

fig. 9 is a diagram of the voltage change in a stabiliser according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Generally, the stabiliser 1 is inserted into a housing 2. The housing 2 further contains a motor 3, to ensure the operation of the stabiliser 1 itself. Advantageously, the motor 3 is a brushless motor, so as to avoid the need for sliding contacts and the formation of sparks resulting therefrom. The stabiliser 1 comprises two fixed windings 4 and 5 and a sliding winding 6, driven by the motor 3; each of the windings 4 to 6 is made of conductor wire, preferably of copper, and is mounted around a respective magnetic core. Such a construction is similar to that of a voltage regulator that works as an auto-transformer (see fig. 7) . The cores of the windings 4 to 6 have substantially the same length. The winding 6 is coaxial to the windings 4, 5. The sliding winding 6 is specifically designed short-circuited. Preferably, the inner diameter of the core of the winding 6 is slightly larger than the external diameter of the windings 4 and 5. Advantageously, the motor 3 performs the axial movement of the sliding winding 6 because of a worm screw mechanism, not shown in the figures. This situation, typical of the voltage regulator, is shown in fig. 7.

According to the present invention, around the windings 4, 5, there are additional windings 7, 8, electromagnetically coupled to the windings 4, 5 and arranged around the same magnetic cores .

Stabiliser 1 acts as a voltage regulator, but, instead of regulating the voltage from 0 V to a maximum value, typical of the particular device, performs a regulation within a range equal to the voltage oscillation range provided by the network to which the stabiliser 1 is connected. Each of the windings 4 to 8 has its own function within stabiliser 1. The windings 4 and 5 have the function of energising the magnetic core and com ¬ pensating for the current imbalance between the input and the output of the stabiliser 1; such compensation is function of the input voltage, that has to be adjusted, and of the regulated output voltage. The winding 6 has the function of arrange itself in a position that can be facing the winding 4, facing the winding 5 or in any intermediate position between these extreme positions. In order to do this, said mobile winding 6 is moved ax- ially with respect to said fixed windings 4, 5; 7, 8 by the motor 3. Finally, the windings 7 and 8 transmit the power passing through the system and have a voltage equal to the change of the required nominal voltage.

The sizing of each of the windings 4 to 8 is extremely important for the proper operation of the stabiliser 1 and is of utmost importance in achieving the desired stabilisation.

The voltage regulated by the output stabiliser 1 is hereafter referred to as V2. The input voltage can oscillate from a minimum value Vl min = V2- AbV2 to a maximum value Vl max = V2 + AaV2. AbV2 and AaV2 may be equal or different from each other. By indicating with V s the turn voltage, the number of turns for each winding can be obtained (except for the winding 6, that will be disclosed in the following) . For winding 4 and winding 5, they will be V2/V s (referred to respectively as N4 and N6) for winding 7, they will be AaV2/V s (referred to as N7) and for winding 8, they will be AbV2/V s (referred to as N8) .

The current delivered by the stabiliser 1 should be referred to as 12. The current supplied to the stabiliser 1 varies from a minimum II = V2l2/Vl max to a maximum II = V2l2/Vl m i n . In the first case, the current passing through the windings 4 and 5 is 14 = 15 = 12-11, in the second case 14 = 15 = 11-12. In any case, 17 = 18 = II. Considering the magnetomotive force acting on the winding 6 M6, equal to M6 = N6I6, there is M6 = N6I6 = N5I5 + N8I8 and M6 = N6I6 = N4I4 + N7I7. Since Vl min < Vl max , in order to take into account the maximum variations, the sizing should be based on the second case, i.e. considering 14 = 15 = 11-12. In this way, it is possible to trace the number of turns for all the windings, depending on the needs and characteristics of the wires forming the windings. It should also be considered that a part 10 of current is needed to energise the system and said current should be added to both 14 and 15; said current 10 is anyway very small and neglecting it does not lead to excessive errors.

The windings 7 and 8 lead to the maximum current required as output, but they are sized only with the voltage Vl m i n and Vlmax , reason for them to only account for the fluctuation that is to be compensated and cancelled.

During operation, the motor 3 moves a worm screw, not shown in the drawings, which operates the translation of the winding 6 in an axial direction, so as to move it from a position facing the winding 4 to a position facing the winding 5 and vice versa, with the possibility to stop at any of the intermediate positions. Using a brushless motor 3 will avoid the sparks that could be generated by an electric motor. Also, the fact that the winding 6 is not in contact with the windings 4, 5 or 7, 8 causes the sparks to be completely avoided, leading to a safety gain and an extension of the operating life of the parts of the stabiliser 1. Preferably, the motor 3 involves a speed reducer, to achieve a more valuable displacement regulation.

Motor 3 is activated by an electronic scale, not shown in the drawings, in feedback with the output voltage to be stabilised. In other words, the voltage change is weighed by the scale, which sends a corresponding signal to the motor 3, causing the winding 6 to move in direction and distance corresponding to the voltage adjustment to be achieved. The voltage variation is continuous, as shown in fig. 9 and not, as with the prior art stabilisers, stepped, as shown in fig. 8. In this way a very precise oscillation compensation is obtained, so that an extremely stable V2 is secured, more stable than with any prior art stabiliser.

The stabiliser according to the present invention thus allows to compensate for the voltage fluctuations precisely obtained, with a continuous compensation, without scintillation events, with a simple construction that can adapt to any type of system, achieving a result never achieved and not even conceivable.

It is understood, however, that the invention is not to be considered as limited by the particular arrangement illustrated above, which represents only an exemplary implementation of the same, but different variants are possible, all within the reach of a person skilled in the art, without departing from the scope of the invention itself, as defined by the following claims.

LIST OF REFERENCE NUMERALS

1 Stabiliser

2 Housing (of 1)

3 Motor (of 6)

4 Fixed winding

5 Fixed winding

6 Sliding winding

7 Additional winding (of 4

8 Additional winding (of 5