POWER FACTOR CORRECTION APPARATUS

FIELD OF INVENTION

THIS INVENTION relates to power factor correction apparatus. The invention has general application to electric power factor correction apparatus for saving electric power in respect of domestic, industrial and commercial power supplies provided in the form of polyphase, alternating current electricity supply. The invention would not normally have application to other electricity supply systems. The present invention has particular application to electric power saving apparatus applicable to inductive load system. However, the invention is not limited to this field of use. BACKGROUND ART

The supply of electrical power by distribution through a power grid, particularly in the form of polyphase, alternating current electricity supply, is prone to efficiency losses. One of the losses which is not normally addressed is the so-called "power factor" — a measure of how effectively power is being used by the system. However, little attention has been given to address power wastage evident in the difference between the active power generated and the apparent power delivered.

The present invention aims to provide electric power saving apparatus which alleviates the abovementioned problems. Other aims and advantages of the invention may become apparent from the following description. DISCLOSURE OF THE INVENTION

With the foregoing in view, the present invention in one aspect resides broadly in electric power saving apparatus for a polyphase alternating current power supply including:

one or more line terminals, the or each line terminal for electrical connection to an active conductor of the alternating current power supply; a neutral terminal for electrical connection to a neutral conductor of the alternating current power supply;

a capacitor electrically connected to the or each line terminal for capacitive isolation of the or each line terminal from the neutral terminal;

a first diode electrically interposed between the or each line terminal and the neutral terminal and having electrical resistance means electrically interposed between the or each first diode and its line terminal; and a second diode electrically interposed between the or each line terminal and the neutral terminal and having electrical resistance means electrically interposed between the or each second diode and the neutral terminal.

For a single phase application, there is one line terminal and correspondingly one of each of the first and second diodes and the associated electrical resistances. Suitably, there is provided a line terminal and its associated components for each phase of the polyphase alternating current power supply. Of course, an integrated unit having sufficient line terminals for the normal power distribution system may be provided to consumers receiving less than all of the available phases, thereby rendering one or more line terminals and their associated components redundant.

Preferably, the diodes are light emitting diodes which may be illuminated by the supplied power when connected across a load. The electric power saving apparatus may be provided as a universal capacity power saver using power factor correction method and preferably as a single module per phase encasing a power factor correction capacitor with an electronic assembly of light emitting diodes as a display module on the front panel. Electric components are housed in a housing, the front panel forming apart thereof, and arranged to have conductors exiting through apertures in either the back or the side for connection to the consumer's switch board line and neutral terminals. These conductors are attached to electrodes and connected to the electrical components as an inner assembly.

Preferably the front panel is removable and contains two apertures for fitting the light omitting diode display module connected to the capacitor assembly inside.

The terminals are connected through appropriate cross sectioned wire conductors to the line or phase wires connected to inductive loads such as motors, transformers, chokes and the like. The second terminal is connected through the appropriate cross sectioned wire conductors to the neutral wire connected to the inductive load such as motor, transformer, choke and the like.

Both the connecting wires are insulated in accordance with local standards connected from the capacitor terminals to the assembly and display module power terminals. A corresponding set up is arranged for three phase four wire systems, three of the wires being for the three respective phases and the fourth wire being for the neutral.

The casing and cover are made of moulded plastic of the type polypropylene or PPCP or talc/silica filled polypropylene or polyethylene terephthalate or glass filled nylon, nylon 66 etc. The selection of the plastics for the casing and cover would be determined by the application and environmental needs. The conductors of appropriate size extend from the terminals up to the three phase four wire connections parallel to the inductive load or motor. An appropriate number of connectors based on the motor horse power can be connected in parallel to provide power factor correction appropriate for that horse power of the motor or load. Thus a minimal number of varied connector sizes can be used to achieve correction for a wide range of motor sizes.

Accordingly, the power factor correction apparatus of the invention is of a modular capacity of power saver form for use with single or three phase inductive motors or loads such as transformers and includes a plastic moulded housing with a cover having terminals for connection and light omitting diode display assembly in the front panel or cover. A single capacitor or a set of three capacitors is mounted along with electronic display. The light omitting diode display assembly is further mounted on the front panel. The capacities often microfarads or multiples of same are mounted inside with polyethylene resin along with electronic and display assembly. In the three phase units, three capacitors of equal value are selected and mounted with the assemblies on top of them. Capacitors of equal sizes and increments such that the combination of separate correctors can be employed to accommodate various sizes of small to medium inductive loads in the range of for example 1 to 100 KVAR. For single phase, a twin terminal is provided at the back and is used whereas for three phase four wire system the connectors are mounted on the top of the panel all four wires of suitable size cross section are brought out from a grommeted aperture in the mounting housing. The LED display is on the front panel. These terminals are connected to both terminals of capacitor with electronic assembly and LED display in case of single phase applications. In the case of a three phase application, the wires of suitable size are connected to four points, three for the phase wires and the fourth for the neutral wire. These sets can be connected in parallel to each other such that each capacitor assembly in individual will be connected to a corresponding capacitor in another assembly, though not necessarily equal to the other set. Thus a combination can be utilised for different sizes of inducting load needing correction of the power factor and such combination can be used to bring back the power factor of the system towards unity.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood and put into practical effect, a preferred embodiment of the present invention will now described with reference to the following drawings, and wherein: Fig. 1 is a diagrammatic representation of electrical components for power factor correction apparatus for single phase power supply according to the invention;

Fig. 2 is a diagrammatic representation showing electrical connections of the electrical components for the power factor correction apparatus of Fig. 1 ;

Fig. 3 is a diagrammatic representation showing . terminal connections for electrical components for the power factor correction apparatus of Fig. 1 ;

Fig. 4 is a diagrammatic representation of electrical components for power factor correction apparatus for three-phase power supply according to the invention

Fig. 5 is a diagrammatic representation of an exemplary physical containment for the electrical components for the power factor correction apparatus of Figs. 1 and 4;

Fig. 6 is a diagrammatic representation showing the terminal connections for the physical containment of Fig. 5 when containing electrical components for the three-phase power factor correction apparatus of Fig. 4; and

Fig. 7 is an oblique view of the containment of Figs. 5 and 6 without the power factor electrical components. DETAILED DESCRIPTION OF THE DRAWINGS

The power factor correction apparatus having electrical components 10 for single phase shown in Figs. 1 to 3 includes a circuit mounting 11 having mounted thereto a terminal ("terminal 1") shown at reference numeral 14 and a terminal ("terminal 2") shown at reference numeral 15. An active conductor 12 is connected from terminal 1 to a power supply (not shown). A neutral conductor 13 is connected from terminal 2 to the power supply. A resistor 18 is interposed in electrical connection between terminal 1 and a light emitting diode (LED) shown at reference numeral 22 through conductors 16 and 20. A resistor 19 is interposed in electrical connection between terminal 2 and another LED 23 through conductors 17 and 21. LED 22is electrically connect directly to terminal 2 by conductor 24 and LED 23 is electrically connect

directly to terminal 1 by conductor 25. A capacitor 28 is electrically interposed between terminal 1 and terminal 2 by conductors 26 and 27 respectively, and it can be seen from Figs. 1 and 3 that the capacitor is used for the mounting of the terminals to which the remainder of the electrical circuit is connected. The power factor correction apparatus shown in Fig. 4 has electrical components 30 in which components in common with those shown and described with respect to Figs 1 to 3 are given the same reference numerals. For the extra two phases, corresponding components are provided to those for a single phase circuit, and in Fig. 4, the corresponding components have reference numerals corresponding to the first phase to 20 has been added to the reference numerals for the second phase and 40 has been added to the reference numerals for the third phase. There is no corresponding component for the LED 22 connected directly to the terminal 2 and through resistor 18 to terminal 1. However, a connection is provided between each phase ahd the other two phases through two resistors in series between LED's by way of the common neutral conductor 13. Electrical connection to the power supply is facilitated by four terminal blocks (shown as a single integrally formed block) for connection to the three phases via terminal blocks 71, 72 and 73 and to the neutral of the supply via terminal block 70.

Either of the circuits may be housed in the housing 75 of Fig. 5, the terminal block 74 for a single phase circuit being shown connected by an extension cable 78 to the remainder of the circuitry (not shown in Fig. 5, being housed internally). As shown in Figs. 6 and 7, the housing has an open box portion 76 to which a lid portion 77 may be fixed to close the open side of the box portion (being the top side in the orientation shown in Fig. 7). The lid portion has a panel 79 to and/or through which the terminals and LED's are mounted. The lid may be fixed by fasteners shown typically at 68 and the box portion has an aperture 69 in one of its side walls into which a grommet 67 may be inserted to provide for the extension cable to penetrate therethrough.

In use, power factor correction apparatus according to ^' the invention may be installed in the electrical distribution or meter box for a customer of a power supply authority or retailer. The power conductors may be connected as described herein to correct the power factor for electrical loads in respect of equipment and/or electrical appliances run by the customer. The equipment and/or appliances would run with greater efficiency and therefore at a lower charge rate. It is believed that the installation of power factor correction apparatus in accordance with the present invention may have a positive effect on reducing power generation capacity requirements for the same number of consumers of systems not having the power factor.correction apparatus installed.

Alternatively, the power factor correction apparatus of the present invention may be provided as a device which may be plugged in to a general purpose outlet.

Although the invention has been described with reference to a specific example, it will be appreciated by those skilled in the art that the invention may be embodied in other forms within the broad scope and ambit of the invention as herein set forth and defined by the following claim.