ZA200807479B

ZA200807479B - Demand control unit

Info

Publication number: ZA200807479B
Application number: ZA200807479A
Authority: ZA
Inventors: Johan Christian Pienaar
Original assignee: Johan Christian Pienaar
Priority date: 2007-11-08
Filing date: 2007-11-08
Publication date: 2010-02-24
Also published as: WO2009062206A1

Description

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NN “ : TECHNICAL FIELD OF THE INVENTION

This invention relates to a device for controlling electricity demand to electrical appliances, and in particular to geysers and especially geysers having dual elements.

BACKGROUND ART

Power outages have become common occurrences, particularly in developing countries where service providers have been unable to keep up with the growth in the power requirements of the population and industry. The shortage in supply forces providers to carry out “load shedding”, where power to non-essential or less essential consumers is cut for hours at a time. This results in considerable disruption to persons and businesses within those areas, as well as loss of income, production and also damage to electrical appliances caused by surges and the like.

Variations in electricity supply are manifested in a decrease in the supply voltage and/or frequency. Typically, the supply frequency is set at 50Hz and this refers to the number of times that the polarity of the alternating current changes.

When supply generators become overloaded, the frequency of their output drops. If it drops below 49.5Hz, these generators can burn out.

One method employed by electricity suppliers to prevent this from happening is ripple control where central control rooms are able to transmit radio frequency signals to disable certain appliances in a defined geographical area. This method relies on the supplier to effect reductions which can disrupt supply to persons within the geographical area even though they are within defined usage criteria.

It is therefore an object of this invention to provide a device which is adapted to respond to changes in the frequency or voltage of power supply relative to an historical baseline, by switching off and on an appliance to which it is connected, or in the case of a dual element geyser, to switching off and on one element thereof. This has the further object of decentralising this function and rendering it a pro-active measure to prevent excessive load rather than a reactive one once the load has o } become too great. It further seeks to localise control of electrical demand at each appliance.

DISCLOSURE OF THE INVENTION

According to the invention, a device for controlling electricity demand to an electrical appliance, comprises a frequency sensing circuit for monitoring the incoming frequency of mains electrical supply; a microprocessor in communication with the sensing circuits for calculating variations in the supply frequency relative to an average or baseline supply; and one or more relay output circuits; the operation of the relay being controlled by the microprocessor in response to the calculated variations in supply, to switch electrical output to the appliance(s). The output channels function independantly in terms of switching characteristics i.e. they are set at different levels.

In one form of the invention the devices further includes a voltage sensing circuit with the microprocessors calculating variations in supply voltage and frequency relative to the baseline supply and switching electrical output accordingly.

In the preferred form of the invention, the device may be single or muilti- output. In other words, there could be two or more channels with different settings.

Typical appliances would have single output — i.e. they are either on or off. Pool pumps, geysers and fin heaters may however have two settings at which they are able to operate.

In the preferred form of the invention, the device is connected in series between the mains supply and the appliance(s).

Also in the preferred form of the invention, the microprocessors establish the average supply voltage and frequency to an appliance over a preset period, and make use of this as a baseline reference against which variations in supply voltage and frequency are measured. Thus in one example, if the input frequency drops by more than 1 Hz or if the input voltage drops by more than 5V, the device will switch off the appliance(s).

- } In the preferred form, the frequency sensing circuit uses opto-isolators to monitor incoming frequency while op-amp circuits are used to monitor incoming . voltage in the voltage sensing circuit.

The microprocessor also includes a power supply unit which generates a 5Vdc power node to power the processor and switching circuits.

The relay output circuit(s) are preferably equipped with at least 16A relays to be able to control and switch any type of geyser element or non-essential electrical appliance, for example a swimming pool pump, spa bath, heater, air conditioner or the like.

The device is preferably further adapted to reverse the switching process a predetermined time after input power supply has been fully restored, for example 20 minutes later, and a suitable timing device is provided within the microprocessor circuitry. The applicant envisages that the devices may be constructed with random time delays preset between 15 and 30 minutes for example, to promote spreading of the load once power supply reverts to normal.

The device of the invention would find particular use with a dual element geyser as a drop in supply would result in initially one of the two elements being switched off should the first threshold level be reached. This would result in a geyser which requires 30 minutes to heat water with both elements operational, taking an hour to heat up. Should a second (lower) threshold be reached, the second element of the dual element geyser being connected to another output of the controller ,will be switched off This is preferably to having no electrical supply and therefore no hot water at all.

The advantage of the device of the invention is that it localises control of electrical demand at each appliance, rather than requiring the electricity service provider having to cut supply completely.

The device may also switch when for example the kitchen stove is on at maximum levels or under any other circumstances causing local supply variations.

= Sh f { 4 & oy ' 3 p LL au 8/ 07 . BRIEF DESCRIPTION OF THE DRAWING - An embodiment of the invention is described below with reference to the accompanying drawing, Figure 1, which is a schematic diagram of a device of the invention. ‘

BEST MODE FOR CARRYING OUT THE INVENTION

In the drawing, the device is located in series between the mains supply and an appliance such as a geyser. The device comprises a power supply unit 10 which powers microprocessor 12. The microprocessor is linked to a frequency sensing circuit 14 and a voltage sensing circuit 16 which monitor the variations in electrical supply relative to a calculated average or baseline. The voltage sensing circuit 16 is optional. Should supply decrease as manifested in a decrease in voltage or frequency of supply, the microprocessor activates the relay output circuit 18 to switch off supply to the appliance 20. In the instances where the appliance is a dual element geyser or similar, it is preferable that only one element is switched off to still permit some heating of water.

For example, where supply frequency drops below 49,76Hz one element may be switched off. If it drops below 49, 56Hz, then the second element is switched off.

Claims

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1. A device for controlling electricity demand to an electrical appliance, characterised in that it comprises a frequency sensing circuit a for monitoring the incoming frequency of mains electrical supply; a microprocessor in communication with the sensing circuits for calculating variations in the supply frequency relative to an average or baseline supply; and one or more relay output circuits; the operation of the relay being controlled by the microprocessor in response to the calculated variations in supply, to switch electrical output to the appliance(s).

2. A device for controlling electricity demand characterised in that the output channels function independantly in terms of switching characteristics.

3. A device for controlling electricity demand according to claim 1 or claim 2 characterised in that it is single output.

4. A device for controlling electricity demand according to claim 1 or claim 2 characterised in that it is multi-output.

5. A device for controlling electricity demand according to any of the above claims characterised in that the device is connected in series between the mains supply and the appliances.

6. A device for controlling electricity demand characterised in that the microprocessors establish the average supply voltage and frequency to an appliance over a preset period, and make use of this as a baseline reference against which variations in supply voltage and frequency are measured.

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7. A device for controlling electricity demand according to any of the above claims characterised in that the frequency sensing circuit uses opto-isolators to . monitor incoming frequency while op-am circuits are used to monitor incoming voltage in the voltage sensing circuit.

8. A device for controlling electricity demand according to any of the above claims characterised in that the microprocessor also includes a power supply unit which generates a 5Vdc power node to power the processor and switching circuits.

9. A device for controlling electricity demand according to any of the above claims characterised in that the relay output circuit(s) are equipped with at least 16A relays to be able to control and switch any type of geyser element or non-essential electrical appliance.

10. A device for controlling electricity demand according to any of the above claims characterised in that it is further adapted to reverse the switching process a predetermined time after input power supply has been fully restored, a suitable timing device being provided within the microprocessor circuitry.

11. A device for controlling electricity demand according to claim 10 characterised in that the timing device is preset with a random time delay in the range 15 to 30 minutes after normal power is restored.

12. A device for controlling electricity demand according to any of the above claims characterised in that the electrical appliance in a dual element geyser, wherein a drop in supply would result in initially one of the two elements being switched off should the first threshold level be reached.

Co - 2008/074¢ Vv - . 13. A device for controlling electricity demand according to claim 12 characterised in that the second element of the dual element geyser is connected to a second . output of the device, this second element being switched off in the event that a second (lower) threshold is reached.

14. A device for controlling electricity demand according to any of the above claims characterised in that it responds to any circumstance affecting local supply variations, for example a high consumption appliance being in operation.

15. A device according to any of the above claims which further includes a voltage sensing circuit in communication with the microprocessor, the variation of supply voltage relative to the baseline supply voltage and frequency being utilized by the microprocessor to switch electrical output to appliances in response thereto. Dated this 19 dayof August 2008 me MORRISON A INC. ~ : APPLICANTS’ PATENT ATTORNEYS