GB2477327A

GB2477327A - Domestic voltage reduction device

Info

Publication number: GB2477327A
Application number: GB1001532A
Authority: GB
Inventors: Paul John Carter
Original assignee: C & C Marshall Ltd
Current assignee: C & C Marshall Ltd
Priority date: 2010-01-29
Filing date: 2010-01-29
Publication date: 2011-08-03
Also published as: WO2011092475A1; GB201001532D0; GB201215133D0; GB2494961A; GB2494961B

Abstract

A voltage control apparatus, for controlling the voltage of a domestic power supply, comprises an electrical input 108, 109 for receiving an electrical supply having an associated input voltage, a voltage control means 101, 102, 103, 104 arranged to receive the electrical supply from the electrical input and to selectively reduce the input voltage, and an electrical output 110, 111 arranged to provide an output supply to a consumer unit, where the output supply has a voltage in accordance with the selectively reduced input voltage. The voltage control means may comprise a voltage reduction device 101, a switching assembly 102, a controller 103 and a current monitoring transformer 104. The voltage reduction device may be a transformer having a plurality of interconnected secondary windings 101 c-f arranged to be selectively connected or bypassed to provide a reduced variable voltage.

Description

Voltage Control Apparatus The present invention relates to an apparatus, system and method for controlling voltage. More specifically, the apparatus of the present invention is arranged to control the voltage of an electrical supply before the electrical supply enters a consumer unit.

In particular, the present invention aims to reduce the input voltage supplied to a consumer unit to thereby reduce resultant energy wastage.

Electricity suppliers provide electrical power via electricity supplies to homes, businesses and industries across a wide geographical area. In Europe, electricity supplies vary in respect of their operating voltage. It has been known for such operating voltages to be from about 210V up to 265V. However, the European Union Voltage Harmonisation directive has defined that all electricity supplies must be provided at 230V +6% -10%, which equates to anything from 207.OV to 243.8V. Given the variations allowable under the European Union Voltage Harmonisation directive there have in fact been few changes in the voltage levels supplied across Europe because most European countries operate off either a 220V or 240V supply, thereby falling within this range.

In order to increase the profitability of mass produced consumer electronic and electrical products many companies manufacture a single product suitable for re-sale across the whole of the European market. As a consequence most electrical items are designed to work at the lower-end of the above-mentioned voltage range, for example 210V to 220V. Operating at the lower end of the allowable voltage range ensures that the product is provided with sufficient operating voltage across the whole of the European market For those countries such as the UK which provide a 240V electricity supply, use of electrical products which have been designed to operate at 220V, as mentioned above, results in any excess voltage which is delivered to the product being dissipated as heat. Hence, in countries such as the UK it is common for 20V of electricity to be constantly wasted by electrical products.

This is a known problem and in order to attempt to tackle the problem various ways forward have been proposed.

One popular solution to the problem has been to utilise a step-down transformer in order to step the 240V supply down to 220V. However, utilising such a transformer can cause problems, for example, if a load of more than 220V is required by a device the device may not be able to function properly.

In order to overcome this problem, systems have been proposed that utilise bypass functionality. Such bypass functionality allows for a transformer that is converting a 240V supply into a 220V supply to be bypassed in favour of the 240V supply when a 240V supply is required.

However, these systems are known to require unduly large transformer components.

Consequently, such systems can be unduly large as well as impractically expensive to produce. Furthermore, the switching of these transformers can cause unwanted spikes in the electrical characteristics of the supply. Hence, partly due to the size and expense of such systems it has generally only been practical to provide such voltage control apparatus in an industrial setting.

Applying these systems in an industrial setting involves installing the devices to operate along side industrial distribution boards. Industrial distribution boards draw large levels of current and therefore the electrical requirements of such voltage control systems have to be designed accordingly. Furthermore, due to the differing power requirements of industrial buildings, such systems require an individual set-up and calibration such that they can operate efficiently in the specific industrial setting. In addition, the current drawn in an industrial setting can vary substantially on an hour-by-hour basis, consequently, known systems usually require large amounts of load or transformer switching in order to compensate for such current variations. The present inventor has therefore realised that it is therefore impractical to utilise similar systems in a domestic setting because the requirements of an industrial setting differ so substantially.

Known voltage control apparatuses are therefore too large, expensive and impractical for use in a domestic setting.

The present invention aims to at least partly mitigate the aforementioned problems of

the prior art.

An embodiment of the present invention also aims to provide a voltage control apparatus, which may reduce power wastage as much as possible.

An embodiment of the present invention aims to provide a voltage control apparatus, which is cheap to manufacture.

An embodiment of the present invention also aims to provide a voltage control apparatus, which is suitable for use in a domestic setting.

An embodiment of the present invention aims to provide a voltage control apparatus, which is capable of operating with large current drawing loads connected.

According to a first aspect of the present invention there is provided a voltage control apparatus for controlling the voltage of a domestic power supply, comprising: an electrical input for receiving an electrical supply having an associated input voltage; a voltage control means arranged to receive the electrical supply from the electrical input and to selectively reduce the input voltage; and an electrical output arranged to provide an output supply to a consumer unit, the output supply having a voltage in accordance with the selectively reduced input voltage.

In an embodiment of the invention, the voltage control means further comprises: a voltage reduction device arranged to reduce the input voltage by subtracting a reduced voltage, derived from the received electrical supply, from the input voltage of the received electrical supply.

In a further embodiment of the invention, the voltage reduction device is a transformer circuit and comprises: a primary winding connected across the electrical input; and a secondary winding having a first terminal connected to a terminal of the electrical input and a second terminal connected to a terminal of the electrical output, the secondary winding arranged such that a negative voltage is induced therein from the electromotive force caused by electric current flowing through the primary winding and the voltage provided at the electrical output is the summation of the input voltage and the negative induced voltage.

In an additional embodiment of the invention, the reduced voltage, which is subtracted from the input voltage of the received electrical supply, is variable.

In an embodiment of the invention, the voltage reduction device comprises a plurality of interconnected secondary windings arranged to selectively be connected or bypassed to provide a variable reduced voltage.

In a further embodiment of the invention, each secondary winding has an associated switch arranged to connect or bypass the respective secondary winding.

In an additional embodiment of the invention, the voltage control means further comprises a switching assembly arranged to switch such that the electrical output is connected to either the received electrical supply or the reduced voltage output supply.

In an embodiment of the invention, the switching assembly is arranged to connect the electrical output to the received electrical supply by providing a short circuit across the voltage reduction device.

In a further embodiment of the invention, the switching assembly is arranged to connect the electrical output to the electrical supply received at the electrical input, and thereby bypass the voltage reduction device, when the voltage reduction device changes a connection state of a secondary winding of the plurality of interconnected secondary windings.

In an additional embodiment of the invention, the switching assembly comprises: a first switch operable to connect the electrical output to the received electrical supply when a current being drawn by the voltage control apparatus is above a threshold; and a second switch, arranged in parallel with the first switch, operable to connect the electrical output to the received electrical supply when the voltage reduction device changes the connection state of a secondary winding of the plurality of interconnected secondary windings.

In an embodiment of the invention, the first switch is a relay and the second switch is a semiconductor-type switch.

In a further embodiment of the invention, the voltage control apparatus further comprises a current monitor arranged to monitor a current being drawn into the voltage control apparatus for determining whether the electrical output should be connected to the received electrical supply or the output supply having a reduced voltage in accordance with the reduced input voltage of the voltage control means.

In an additional embodiment of the invention, the voltage control apparatus further comprises a controller for controlling the operation of the voltage control apparatus.

In an embodiment of the invention, the voltage control apparatus is provided with a consumer unit in a common housing such that electrical output of the voltage control apparatus can provide an input to the remainder of the consumer unit.

According a further aspect of the present invention there is provided a voltage control apparatus, comprising: an electrical input for receiving an electrical supply having an associated input voltage; a voltage control means arranged to receive the electrical supply from the electrical input, the voltage control means comprising: a voltage reduction device arranged to selectively reduce the input voltage by subtracting a reduced voltage, derived from the received electrical supply, from the input voltage of the received electrical supply; and an electrical output arranged to provide an output supply, the output supply having a voltage in accordance with the selectively reduced input voltage.

In an embodiment of the invention, the voltage reduction device is a transformer circuit and comprises: a primary winding connected across the electrical input; and a secondary winding having a first terminal connected to a terminal of the electrical input and a second terminal connected to a terminal of the electrical output, the secondary winding arranged such that a negative voltage is induced therein from the electromotive force caused by electric current flowing through the primary winding and the voltage provided at the electrical output is the summation of the input voltage and the negative induced voltage.

In a further embodiment of the invention, the reduced voltage, which is subtracted from the input voltage of the received electrical supply, is variable.

In an additional embodiment of the invention, the voltage reduction device comprises a plurality of interconnected secondary windings arranged to selectively be connected or bypassed to provide a variable reduced voltage.

In an embodiment of the invention, each secondary winding has an associated switch arranged to connect or bypass the respective secondary winding.

In a further embodiment of the invention, the voltage control means further comprises: a switching assembly arranged to switch such that the electrical output is connected to either the received electrical supply or the reduced voltage output supply.

In an additional embodiment of the invention, the switching assembly is arranged to connect the electrical output to the received electrical supply by providing a short circuit across the voltage reduction device.

In an embodiment of the invention, the switching assembly is arranged to connect the electrical output to the electrical supply received at the electrical input, and thereby bypass the voltage reduction device, when the voltage reduction device changes a connection state of a secondary winding of the plurality of interconnected secondary windings.

In a further embodiment of the invention, the switching assembly comprises: a first switch operable to connect the electrical output to the received electrical supply when a current being drawn by the voltage control apparatus is above a threshold; and a second switch, arranged in parallel with the first switch, operable to connect the electrical output to the received electrical supply when the voltage reduction device changes the connection state of a secondary winding of the plurality of interconnected secondary windings.

In an additional embodiment of the invention, the first switch is a relay and the second switch is a semiconductor-type switch.

In an embodiment of the invention, the voltage control apparatus further comprises a current monitor arranged to monitor a current being drawn into the voltage control apparatus for determining whether the electrical output should be connected to the received electrical supply or the output supply having a reduced voltage in accordance with the reduced input voltage of the voltage control means.

In a further embodiment of the invention, the voltage control apparatus further comprises a controller for controlling the operation of the voltage control apparatus.

According to a further aspect of the present invention there is provided a voltage control system, comprising: a voltage control apparatus according to any of the aforementioned embodiments of the invention; and a consumer unit arranged to receive the output supply of the electrical output of the voltage control apparatus and provide a plurality of output supplies derived from the electrical output of the voltage control apparatus.

According to another aspect of the present invention there is provided a method for controlling the voltage of a domestic power supply, comprising: receiving an electrical supply having an associated input voltage; selectively reducing the input voltage; and providing an output supply to a consumer unit, the output supply having a voltage in accordance with the selectively reduced input voltage.

In an embodiment of the invention, the step of selectively reducing the input voltage comprises subtracting a reduced voltage, derived from the electrical supply, from the input voltage.

In a further embodiment of the invention, the reduced voltage is produced by: providing a primary winding connected across an electrical input such that when current flows through the primary winding an electromotive force is produced; and providing a secondary winding having a first terminal connected to a terminal of the electrical input and a second terminal connected to a terminal of an electrical output; wherein the electromotive force produced by the primary winding induces a negative voltage in the secondary winding such that a voltage provided at the electrical output is the summation of the input voltage and the negative induced voltage.

In an additional embodiment of the invention, the step of selectively reducing the input voltage further comprises varying the reduction of the input voltage.

In an embodiment of the invention, the method further comprises determining whether to connect or bypass each of a plurality of interconnected secondary windings to provide a variable reduced voltage.

In a further embodiment of the invention, the method further comprises providing a short circuit across a voltage reduction device, which selectively reduces the input voltage, such that the electrical output is connected to the received electrical supply.

In an additional embodiment of the invention, the method further comprises connecting the electrical output to the electrical supply received at the electrical input when the voltage reduction device changes a connection state of a secondary winding of the plurality of interconnected secondary windings.

In an embodiment of the invention, the method further comprises monitoring a current being drawn; and selectively reducing the input voltage according to the current being drawn.

According to yet another embodiment of the present invention there is provided a method for controlling voltage, comprising: receiving an electrical supply having an associated input voltage; selectively reducing the input voltage by subtracting a reduced voltage, derived from the electrical supply, from the input voltage; and providing an output supply, the output supply having a voltage in accordance with the selectively reduced input voltage.

In an embodiment of the invention, the step of selectively reducing the input voltage comprises.

In an embodiment of the invention the method further comprises determining whether to connect or bypass each of a plurality of interconnected secondary windings to provide a variable reduced voltage.

In a further embodiment of the invention the method further comprises providing a short circuit across a voltage reduction device, which selectively reduces the input voltage, such that the electrical output is connected to the received electrical suppIy In an additional embodiment of the invention the method further comprises connecting the electrical output to the electrical supply received at the electrical input when the voltage reduction device changes a connection state of a secondary winding of the plurality of interconnected secondary windings.

In an embodiment of the invention the method further comprises monitoring a current being drawn; and selectively reducing the input voltage according to the current being drawn.

In yet another embodiment of the present invention the voltage control means provides a fixed reduction in the voltage. In particular, a predetermined voltage reduction is provided by a transformer which is either placed in an ON or OFF state in order to output a reduced or fuI voltage respectively.

Embodiments of the present invention provide a voltage control apparatus that reduces power wastage. Such power reduction is possible because the voltage control apparatus feeds a reduced voltage electricity supply to a consumer unit, the consumer unit then uses this reduced supply for all loads. Power is also saved by the simplicity of the circuit used to provide the voltage reduction because power wastage due to heat dissipation is minimised.

Embodiments of the present invention also provide a voltage control apparatus which is cheap to manufacture. In particular, the transformer arrangement used to provide the step down voltage does not require expensive transformer components and can therefore make significant savings over known step-down transformer systems.

Furthermore, semiconductor switches can be used in the place of power transformers

as has been known to be required in the prior art.

Embodiments of the present invention provide a voltage control apparatus, which is suitable for use in a domestic setting. It is possible to utilise the present invention in a domestic setting because the transformer has been optimised for the lower power requirements of the domestic setting. Furthermore, the design of the voltage control apparatus of the present invention allows for the apparatus to be small, and inexpensive to produce, thus being suitable for the domestic setting. In addition, the specific transformer arrangement, and in particular the way in which it reduces the voltage is more suited to the domestic setting.

As mentioned above, the present invention is suitable for use in a domestic environment, for example in a private house or apartment, and it is also suitable for use in other environments with similar power requirements, such as light industrial or retail environments.

The unit of the present invention is suitably configured so that power dissipated in the unit is a small proportion of the maximum power capacity of the consumer unit, being preferably less than 10% of the power capacity.

Embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a standard consumer unit; Figure 2 shows a consumer unit and voltage control apparatus according to an embodiment of the present invention; and Figure 3 shows a detailed view of a voltage control apparatus provided in accordance with an embodiment of the present invention.

Throughout the description and drawings like reference numerals shall refer to like parts.

Figure 1 shows a standard consumer unit 10 provided and connected as is known in the art. A consumer unit is a device which is installed within all homes, offices and light industrial or retail buildings at the point of entry of the electricity supply. A consumer unit is a device that distributes an electricity supply throughout a building, taking a single input power supply and splitting the supply into a plurality of supplies which can be separately distributed to different circuits or devices within the building. The consumer unit preferably not only splits the electricity supply into a plurality of circuits or channels, but also provides individual circuit breakers and fuses for each of these portions.

In the UK, such consumer units must comply with the requirements of the 17"' Wiring Regulations 6S7671. As a consequence, such units also include a Residual Current Device (RCD), which detects problems such as current leakage within the load being supplied. Furthermore, such consumer units are generally arranged to provide a current of up to about 50A.

As shown in Figure 1 the consumer unit 10 is provided with a main switch 12. The supply lines 11, which carry the incoming electricity supply, connect directly to the main switch 12. The main switch 12 therefore provides a single switching point which can stop all electricity from entering the consumer unit, and therefore the building or area that the consumer unit supplies. The main switch is arranged to trip, that is automatically switch off, if, for example, an excess current is drawn.

The consumer unit 10 splits the electricity supply, after it has passed through the main switch 12 into a plurality of different portions. As mentioned above these portions may correspond to particular devices to be powered, or to a particular group or area of devices. Each portion is provided with an output port 14a-d, which allows for an electrician to connect a device or further network of devices to that portion of the consumer unit 10. Between the main switch 12 and each output port 14a-d a miniature circuit breaker (MCB) 13a-d or DIN-rail mounted circuit breaker is provided. These circuit breakers 1 3a-d are arranged to provide a means for automatically preventing electricity to flow to that portion in the event that an excess current is drawn, possibly due to a short circuit or the like. Hence, the circuit breakers 13a-d act as a safety device.

In a standard consumer unit, as depicted in Figure 1 and described above, the voltage received at the input of the consumer unit is transferred to each output provided by the consumer unit. Consequently, when such a consumer unit 101 is used in the UK it outputs 240V to each portion. Devices connected to the consumer unit, or a portion thereof, requiring only 220V to operate will, therefore, waste power.

Figure 2 shows how a voltage control apparatus 100 of an embodiment of the present invention can be connected between the supply lines 11, which carry the incoming electricity supply, and the consumer unit 10. Providing the voltage control apparatus in this location means that 220V can be provided to the whole consumer unit and all devices connected thereto. Consequently, energy wastage can be minimised.

It will be appreciated that the voltage control apparatus need not be totally separate from the consumer unit and could instead be housed with the consumer unit within a common enclosure. In such a case the voltage control apparatus would effectively form the first stage of the new improved consumer unit, with the voltage control apparatus placed before or upstream of the electrical distribution features of a standard consumer unit. In different embodiments of the invention it would be possible to place the voltage control apparatus before or after a main switch of the consumer unit. It is envisaged that there would be various ways of integrating the voltage control apparatus with the consumer unit such that the functionality of the voltage control apparatus is provided upstream of the distribution functionality of the consumer unit.

Figure 3 provides a more detailed illustration of a voltage control apparatus in accordance with an embodiment of the present invention.

The voltage control apparatus of Figure 3 is arranged suitable for use in a domestic setting. For example, the voltage control apparatus is for use in a domestic environment such as a house, or apartment, and also in any environment having similar power requirements such as a light industrial building, or retail outlet.

The voltage control apparatus 100 of Figure 3 includes a voltage control means including a voltage reduction device 101, a switching assembly 102, a controller 103, and a current monitoring transformer 104. The voltage control apparatus 100 also comprises a plurality of miniature circuit breakers (MCBs) 105, 106 and a thermal switch 107.

The voltage control means is arranged for reducing the input voltage, for example from 240V to 220V. The switching assembly is provided to bypass the functionality of the voltage reduction device, which carries out the voltage reduction from 240V to 220V, when a controller determines, by a measurement obtained from the current monitoring transformer, that more power is being drawn by the load. A voltage control apparatus is therefore provided, which is suitable for feeding a consumer unit.

The voltage control apparatus of Figure 3 and each of its elements shall now be described in detail.

An electrical input is provided by a live electrical input supply line 108 and a neutral electrical input supply line 109. The electrical input is arranged to receive the electrical supply prior to the electrical supply entering the consumer unit or any other device.

When utilised in a domestic setting the electrical input is arranged to receive the electrical supply entering the house or apartment such that the voltage control apparatus feeds the consumer unit for the house or apartment.

The live electrical input supply line 108 and the neutral electrical input supply line 109 will generally be wires/cables, preferably of a thickness matching the wires/cables that carry the electrical supply to the house or apartment. In some embodiments of the present invention special connectors are provided in order to connect the live electrical input supply line 108 and the neutral electrical input supply line 109 to the supply entering the house or apartment.

An electrical output comprising a live output terminal 110 and a neutral output terminal 111 is provided. The voltage control apparatus 100 is arranged to control the voltage received at the electrical input and then provide a voltage at the electrical output derived from the electrical input. Any device that connects to the live output terminal and neutral output terminal 111 should effectively receive the electrical supply which passes through the voltage control apparatus as it would if the voltage control apparatus were not there, except that the voltage of the electrical supply may have been controlled by, for example, reducing the voltage.

The live output terminal 110 and the neutral output terminal 111 are arranged to connect to the input of a consumer unit. Hence, it may be necessary to provide the live output terminal 110 and the neutral output terminal 111 with connectors such it is quick and simple to connect the voltage control apparatus 100 to the consumer unit.

The current monitoring transformer 104 is connected to the live electrical input supply line. In particular, one terminal of a first coil of the transformer is directly connected to the live electrical input supply line 108, while the other end of the first coil of the transformer is both connected to a portion of the switching assembly 102 and a portion of the voltage control means 101. The terminals of the second coil of the transformer are connected to the controller 103.

In operation, when a load (not shown) draws current through the voltage control apparatus 100, the current firstly passes through the current monitor 104. The current monitor works as follows.

As current is drawn by a load (not shown) connected to the output of the voltage control apparatus 100 current will flow through the first coil of current monitor 104 and induce a current in the windings of the second coil of current monitor 104. The induced current is indicative of the load and therefore current being drawn by the voltage control apparatus. The controller 103 can then monitor the current flowing through the second coil to determine the current being drawn by the voltage control apparatus 100. As discussed in more detail later, the controller 103 can then determine whether to switch the switching assembly 102 in accordance with whether or not it is determined that an excessive current is being drawn.

The voltage reduction device 101 provides the means for reducing the voltage and therefore saving energy. In this embodiment of the present invention the voltage reduction device is a transformer apparatus, and is arranged to step-down the input voltage such that energy is not dissipated as heat. Furthermore, a laminated transformer is used as the basis of the transformer apparatus. A laminated transformer is cheaper and smaller than many other types of transformer. However, alternative types of transformer could be used. The characteristics of the transformer utilised in this embodiment of the present invention are advantageous in an industrial setting.

In this embodiment of the present invention the transformer apparatus is arranged to have a voltage of 240V applied across its input, and provide a voltage of approximately 220V across its output. It will be appreciated that the present invention could be utilised with different input and output voltage as well as different step-down ratios.

The reduction from 240V to 220V is therefore provided as an example of this particular embodiment of the present invention.

The voltage reduction device 101 comprises a primary winding lOla, which is connected between the live electrical input supply line 108 and the neutral electrical input supply line 109. The input voltage is therefore applied across the primary winding lOla. A transformer core lOib is then provided adjacent to the primary winding lOla.

The voltage reduction device 101 also includes a plurality of secondary windings lOic-f.

In this embodiment of the invention four secondary windings lOlc-f are utilised, however, it will be appreciated that any number of secondary windings could be used.

Furthermore, it may be desired to only provide a single secondary winding, If a single secondary winding were used this could be accompanied by an arrangement that allowed the single winding to provide a variable voltage, or could form part of a simpler fixed, non-variable voltage reduction device providing a fixed voltage drop.

The four secondary windings lOlc-f are each connected to an individual switching arrangement. The switching arrangement of the first secondary winding lOIc has a switching member connected at one end to both the current monitoring transformer 104 and the switching arrangement 102. The switching arrangement of each winding is preferably in the form of a single pole triple throw relay. Since the current monitoring transformer 104 passes the current drawn by the load, the switching member of the first secondary winding lOic is effectively connected directly to the live electrical input supply line 108. This switching member is then arranged to connect the live electrical input supply line either to the first or second terminal of the first secondary winding 101 c. The second terminal of the first secondary winding 101 c is then connected to the switching member of the second secondary winding lOld. Consequently, if the switching member of the first secondary winding lOic is connected to the first terminal of the first secondary winding 101 c, electric current is arranged to flow through the first secondary winding. Alternatively, if the switching member of the first secondary winding lOic is connected to the second terminal of the first secondary winding lOlc then the first secondary winding is bypassed.

Each of the secondary windings lOlc-f is connected in exactly the same way such that a cascade of windings is provided. The second terminal of the fourth secondary winding lOif then provides the live output terminal.

In operation, when each of the four secondary windings lOlc-f are connected the voltage provided between the live output terminal 110 and the neutral output terminal 111, which is directly connected to the neutral electrical input supply line, is equal to the sum of the input voltage minus the negative voltage produced in each of the secondary windings lOlc-f by the electromotive force (emf) induced in those windings by the electromotive force produced by the primary winding lOla. Hence, the output voltage is the result of the input voltage with the sum of the negative voltages produced by each of the secondary windings subtracted therefrom.

The negative voltage produced by each of the secondary windings 101 c-f can be set by the ratio of turns of each secondary winding when compared to the number of turns of the primary winding. Such concepts of winding ratios are commonly known in the art.

By switching some of the switching arrangements of the secondary windings 101 c-f ON and others OFF, different voltage drops can be achieved, thereby providing a variable voltage reduction device. Clearly, there is a balance to be struck with respect to the number of secondary windings provided. The more windings that are provided will allow for smaller steps in voltage, which may be advantageous. However, as the number of windings increase so does the complexity and efficiency of the apparatus.

In addition, it is preferable that the number of windings provided by each of the secondary windings lOlc-f is equal such that switching of the secondary windings lOlc-f provides a controlled and measured change in the voltage reduction. However, in alternative embodiments of the invention it may be preferable for each secondary winding to have a different number of windings.

While in the present embodiment a variable voltage reduction switching arrangement is provided that utilises a series connection of individual cascaded secondary windings, in alternative embodiments of the present invention other means for providing a variable voltage could be provided. For example, a single secondary coil could be provided with a sliding variable adjustment mechanism. Alternative known means for varying the voltage in a transformer could be utilised. However, the above-described embodiment of the present invention is a preferred arrangement because it allows for simple control of the variation of the voltage provided by the voltage reduction device.

Each of the switching members of the secondary windings lOlc-f is controlled by controller 103. In particular, the controller determines the input voltage in accordance with the current monitored by the current monitoring transformer 104. From the input voltage, which may in itself be variable, the controller is arranged to determine the voltage reduction that is required to provide an output voltage of approximately 220V.

The controller then switches each of the switching members of the secondary windings 101 c-f to control the flow of current through the windings, and as a consequence the voltage drop provided is controlled. In the embodiment illustrated by Figure 3 each of the switching members is connected to each respective first terminal of each secondary winding 101 c-f and therefore the maximum voltage reduction is provided.

Hence, the voltage reduction device 101 of this embodiment of the present invention allows for a variable reduction in the voltage by use of a transformer based circuit. In particular, a transformer based circuit which subtracts a voltage, derived from the input voltage, from the input voltage to produce a reduced voltage. This system allows for a smaller more efficient voltage reduction, which is consequently much more suitable for use in a domestic environment.

We shall now consider the switching assembly 102 in more detai'. The switching assembly 102 is arranged to provide a bypass functionality with respect to the voltage reduction device 101 in the event that a voltage greater than 220V needs to be supplied. In particular, the switching assembly 102 bypasses the voltage reduction device 101 and outputs the input voltage of 240V.

As shown in Figure 3, switching assembly 102 is connected at a first terminal to the current monitor 104 and switching member of the first secondary winding lOic of the voltage reduction device 101 and at a second side to the live output terminal 110.

Hence, a voltage equivalent to the voltage drop provided by the voltage reduction device 101 is provided across switching assembly 102 when the switching assembly 102 is in an open state.

The switching assembly 102 is provided such that, for example, if the input voltage is found to get too low for the voltage reduction to be advantageous, or the power being drawn by the load requires a higher output voltage, then the switching assembly 102 can be switched ON. By switching the switching assembly 102 to the ON state the live electrical input supply line 108 can be directly connected to the output terminal 110 such that the output voltage is the same as the input voltage. Hence, when the switching assembly 102 is switched to the ON state it provides a short circuit across the secondary windings lOlc-f of the voltage reduction device 101 such that the voltage reduction device 101 is effectively deactivated.

In this embodiment of the present invention the switching assembly 102 comprises a relay (not illustrated), which when activated connects the live electrical input supply line 108 to the output terminal 110. The relay is operated by the controller 103, which can determine the input voltage and current being drawn by the current monitoring transformer 104. If the input voltage gets too low or the current being drawn by the load is too high, the controller 104 sends a switching signal to the switching assembly 102 such that the relay 102 is activated and therefore allows for the input voltage to be provided at the output.

In addition to acting as a means for outputting the input voltage, the switching assembly 102 is also switched to the ON state during regulation changes. That is the switching assembly 102 is switched to the ON state whenever the controller 103 switches one of the switching arrangements of the secondary windings lOlc-f of the voltage reduction device 101. The bypass functionality of the switching assembly 102 is then used in order to avoid any interruptions to the supply output by the voltage control apparatus 100. Overall this functionality ensures that the regulation switching is both smooth and also overcomes the problems of "switching transients", which can otherwise occur.

In order to provide for improved switching during regulation changes it is preferable to provide a semiconductor switch in parallel with the relay. The semiconductor switch is therefore used for switching during regulation changes and the relay is used in the circumstances discussed in detail above. Using a semiconductor switch allows for improved prevention of switching transients, particularly as the regulation changes could be frequent. Furthermore, a semiconductor switch is cheap, fast acting, and long lasting.

In the embodiment of the present invention as shown in Figure 3 a plurality of miniature circuit breakers (MCBs) 105,106 are provided. The MCBs are provided in order to attempt to protect the circuit from overload or short circuit. A first MCB 105 is provided between the live electrical input supply line 108 and a first terminal of the primary winding lOla of the voltage reduction device 101. A second MCB is provided between a second terminal of the fourth secondary winding lOlf and the output terminal 110.

The embodiment of the present invention shown in Figure 3 also includes a thermal switching device 107. The thermal switching device 107 is arranged between the second MCB 106 and the output terminal 110. This switching device is provided to be placed in an ON position in the normal state and if it is sensed that the voltage reduction device 101 is overheating then it switches to the OFF position.

The thermal switching device 107 may have the functionality to sense the temperature of the voltage reduction device completely integrated with the switching functionality.

However, in the preferred embodiment of the present invention the sensing is carried out by the controller, or a sensing apparatus connected to the controller, and the controller then provides a switching signal to the thermal switching device 107 when necessary.

The controller 103, which has so far been described with reference to each of the other components of the voltage control apparatus 100 is a microcontroller. It can take the form of a programmable logic device such as an FPGA, or be a specifically designed microprocessing device combined with specific memory functionality. In addition, the controller must be provided with the functionality to drive the relay of the switching assembly 102, particularly if a common 12V relay is used.

The controller 103 is arranged for monitoring the current passing through the current monitoring transformer. Once a current is determined the controller 103 is able to determine the current input voltage and load being drawn. Consequently, the controller 103 is able to control the operation of the switching members of the secondary windings 101 c-f of the voltage reduction device 101 in accordance with calculations as to the required output voltage, given the input voltage. Furthermore, the controller 103 is able to control the switching of switching assembly 102. In addition, the controller can control switching of the thermal switching device 107.

The voltage control apparatus may be provided with a user display. The display can take the form of an LCD-type display or the like. The display can provide information such as the current voltage output and the energy savings being made by the device.

Furthermore, user controls can also be provided along with the user display in order to allow the user to manually operate the switching of both the switching members of the secondary windings lOlc-f of the voltage reduction device 101 and the switching assembly 102.

The addition of automatic power-factor correction into the apparatus would be advantageous for various reasons, for example, the power consumption would be further reduced.

The above described embodiments of the present invention have only been provided as examples and it will be appreciated that various other embodiments of the invention are possible without departing from the scope of the appended claims.

Claims

CLAIMS: 1. A voltage control apparatus for controlling the voltage of a domestic power supply, comprising: an electrical input for receiving an electrical supply having an associated input voltage; a voltage control means arranged to receive the electrical supply from the electrical input and to selectively reduce the input voltage; and an electrical output arranged to provide an output supply to a consumer unit, the output supply having a voltage in accordance with the selectively reduced input voltage.
2. The voltage control apparatus according to claim 1, wherein the voltage control means further comprises: a voltage reduction device arranged to reduce the input voltage by subtracting a reduced voltage, derived from the received electrical supply, from the input voltage of the received electrical supply.
3. The voltage control apparatus according to claim 2, wherein the voltage reduction device is a transformer circuit and comprises: a primary winding connected across the electrical input; and a secondary winding having a first terminal connected to a terminal of the electrical input and a second terminal connected to a terminal of the electrical output, the secondary winding arranged such that a negative voltage is induced therein from the electromotive force caused by electric current flowing through the primary winding and the voltage provided at the electrical output is the summation of the input voltage and the negative induced voltage.
4. The voltage control apparatus according to claims 2 or 3, wherein the reduced voltage, which is subtracted from the input voltage of the received electrical supply, is variable.
5. The voltage control apparatus according to claim 4, wherein the voltage reduction device comprises a plurality of interconnected secondary windings arranged to selectively be connected or bypassed to provide a variable reduced voltage.
6. The voltage control apparatus according to claim 5, wherein each secondary winding has an associated switch arranged to connect or bypass the respective secondary winding.
7. The voltage control apparatus according to any preceding claim, wherein the voltage control means further comprises: a switching assembly arranged to switch such that the electrical output is connected to either the received electrical supply or the reduced voltage output supply.
8. The voltage control apparatus according to claim 7 when dependent on any one of claims 2 to 6, wherein the switching assembly is arranged to connect the electrical output to the received electrical supply by providing a short circuit across the voltage reduction device.
9. The voltage control apparatus according to claim 7 when dependent on claim 5 or 6, wherein the switching assembly is arranged to connect the electrical output to the electrical supply received at the electrical input, and thereby bypass the voltage reduction device, when the voltage reduction device changes a connection state of a secondary winding of the plurality of interconnected secondary windings.
10. The voltage control apparatus according to claim 9, wherein the switching assembly comprises: a first switch operable to connect the electrical output to the received electrical supply when a current being drawn by the voltage control apparatus is above a threshold; and a second switch, arranged in parallel with the first switch, operable to connect the electrical output to the received electrical supply when the voltage reduction device changes the connection state of a secondary winding of the plurality of interconnected secondary windings.
11. The voltage control apparatus according to claim 10, wherein the first switch is a relay and the second switch is a semiconductor-type switch.
12. The voltage control apparatus according any preceding claim, further comprising: a current monitor arranged to monitor a current being drawn into the voltage control apparatus for determining whether the electrical output should be connected to the received electrical supply or the output supply having a reduced voltage in accordance with the reduced input voltage of the voltage control means.
13. The voltage control apparatus according to any preceding claim, further comprising a controller for controlling the operation of the voltage control apparatus.
14. The voltage control apparatus according to any preceding claim wherein the voltage control apparatus is provided with a consumer unit in a common housing such that electrical output of the voltage control apparatus can provide an input to the remainder of the consumer unit.
15. A voltage control apparatus, comprising: an electrical input for receiving an electrical supply having an associated input voltage; a voltage control means arranged to receive the electrical supply from the electrical input, the voltage control means comprising: a voltage reduction device arranged to selectively reduce the input voltage by subtracting a reduced voltage, derived from the received electrical supply, from the input voltage of the received electrical supply; and an electrical output arranged to provide an output supply, the output supply having a voltage in accordance with the selectively reduced input voltage.
16. The voltage control apparatus according to claim 15, wherein the voltage reduction device is a transformer circuit and comprises: a primary winding connected across the electrical input; and a secondary winding having a first terminal connected to a terminal of the electrical input and a second terminal connected to a terminal of the electrical output, the secondary winding arranged such that a negative voltage is induced therein from the electromotive force caused by electric current flowing through the primary winding and the voltage provided at the electrical output is the summation of the input voltage and the negative induced voltage.
17. The voltage control apparatus according to claims 15 or 16, wherein the reduced voltage, which is subtracted from the input voltage of the received electrical supply, is variable.
18. The voltage control apparatus according to claim 17, wherein the voltage reduction device comprises a plurality of interconnected secondary windings arranged to selectively be connected or bypassed to provide a variable reduced voltage.
19. The voltage control apparatus according to claim 18, wherein each secondary winding has an associated switch arranged to connect or bypass the respective secondary winding.
20. The voltage control apparatus according to any one of claim 15 to 19, wherein the voltage control means further comprises; a switching assembly arranged to switch such that the electrical output is connected to either the received electrical supply or the reduced voltage output supply.
21. The voltage control apparatus according to claim 20 when dependent on any one of claims 2 to 6, wherein the switching assembly is arranged to connect the electrical output to the received electrical supply by providing a short circuit across the voltage reduction device.
22. The voltage control apparatus according to claim 20 when dependent on claim 18 or 19, wherein the switching assembly is arranged to connect the electrical output to the electrical supply received at the electrical input, and thereby bypass the voltage reduction device, when the voltage reduction device changes a connection state of a secondary winding of the plurality of interconnected secondary windings.
23. The voltage control apparatus according to claim 22, wherein the switching assembly comprises: a first switch operable to connect the electrical output to the received electrical supply when a current being drawn by the voltage control apparatus is above a threshold; and a second switch, arranged in parallel with the first switch, operable to connect the electrical output to the received electrical supply when the voltage reduction device changes the connection state of a secondary winding of the plurality of interconnected secondary windings.
24. The voltage control apparatus according to claim 23, wherein the first switch is a relay and the second switch is a semiconductor-type switch.
25. The voltage control apparatus according to any one of claims 15 to 24, further comprising: a current monitor arranged to monitor a current being drawn into the voltage control apparatus for determining whether the electrical output should be connected to the received electrical supply or the output supply having a reduced voltage in accordance with the reduced input voltage of the voltage control means.
26. The voltage control apparatus according to any one of claims 15 to 25, further comprising a controller for controlling the operation of the voltage control apparatus.
27. The voltage control apparatus according to any one of claims 15 to 16 wherein the voltage control apparatus is provided with a consumer unit in a common housing such that electrical output of the voltage control apparatus can provide an input to the remainder of the consumer unit.
28 A voltage control system, comprising: a voltage control apparatus according to any one of claim 1 to 27; and a consumer unit arranged to receive the output supply of the electrical output of the voltage control apparatus and provide a plurality of output supplies derived from the electrical output of the voltage control apparatus.
29. A method for controlling the voltage of a domestic power supply, comprising: receiving an electrical supply having an associated input voltage; selectively reducing the input voltage; and providing an output supply to a consumer unit, the output supply having a voltage in accordance with the selectively reduced input voltage.
30. The method according to claim 29, wherein the step of selectively reducing the input voltage comprises subtracting a reduced voltage, derived from the electrical supply, from the input voltage.
31. The method according to claim 30, wherein the reduced voltage is produced by: providing a primary winding connected across an electrical input such that when current flows through the primary winding an electromotive force is produced; and providing a secondary winding having a first terminal connected to a terminal of the electrical input and a second terminal connected to a terminal of an electrical output; wherein the electromotive force produced by the primary winding induces a negative voltage in the secondary winding such that a voltage provided at the electrical output is the summation of the input voltage and the negative induced voltage.
32. The method according to any one of claims 29 to 31, wherein the step of selectively reducing the input voltage further comprises varying the reduction of the input voltage.
33. The method according to claim 32, further comprising: determining whether to connect or bypass each of a plurality of interconnected secondary windings to provide a variable reduced voltage.
34. The method according to any one of claims 29 to 33, further comprising: providing a short circuit across a voltage reduction device, which selectively reduces the input voltage, such that the electrical output is connected to the received electrical supply.
35. The method according to claim 33, further comprising: connecting the electrical output to the electrical supply received at the electrical input when the voltage reduction device changes a connection state of a secondary winding of the plurality of interconnected secondary windings.
36. The method according any one of claims 29 to 35, further comprising: monitoring a current being drawn; and selectively reducing the input voltage according to the current being drawn.
37. A method for controlling voltage, comprising: receiving an electrical supply having an associated input voltage; selectively reducing the input voltage by subtracting a reduced voltage, derived from the electrical supply, from the input voltage; and providing an output supply, the output supply having a voltage in accordance with the selectively reduced input voltage.
38. The method according to claim 37, wherein the step of selectively reducing the input voltage comprises.
39. The method according to claim 38, wherein the reduced voltage is produced by: providing a primary winding connected across an electrical input such that when current flows through the primary winding an electromotive force is produced; and providing a secondary winding having a first terminal connected to a terminal of the electrical input and a second terminal connected to a terminal of an electrical output; wherein the electromotive force produced by the primary winding induces a negative voltage in the secondary winding such that a voltage provided at the electrical output is the summation of the input voltage and the negative induced voltage.
40. The method according to any one of claims 37 to 39, wherein the step of selectively reducing the input voltage further comprises varying the reduction of the input voltage.
41. The method according to claim 40, further comprising: determining whether to connect or bypass each of a plurality of interconnected secondary windings to provide a variable reduced voltage.
42. The method according to any one of claims 37 to 41, further comprising: providing a short circuit across a voltage reduction device, which selectively reduces the input voltage, such that the electrical output is connected to the received electrical supply.
43. The method according to claim 41, further comprising: connecting the electrical output to the electrical supply received at the electrical input when the voltage reduction device changes a connection state of a secondary winding of the plurality of interconnected secondary windings.
44. The method according any one of claims 37 to 43, further comprising: monitoring a current being drawn; and selectively reducing the input voltage according to the current being drawn.
45. Apparatus as hereinbefore described with reference to Figures 2 and/or 3.
46. A method as hereinbefore described with reference to Figures 2 and/or 3.