Field of the Invention

The invention relates to an electricity generating system for generating electrical output.

Background to the invention

Generators utilising internal combustion engines powered by liquid fossil fuels like petrol, diesel, and liquid petroleum gas (LPG) for providing mechanical energy in portable electric generators are well known in the art.

Disadvantages of combustible engine driven generators include high running cost, noise pollution and harmful gas emissions.

The applicant having considered the above proposes the invention described hereunder.

Summary of the Invention

According to the invention there is provided an electricity generating system which includes: an electrically driven motor, the speed of which is controlled by a variable frequency drive; the electrically driven motor operatively coupled to an alternator, the alternator being configured yield electrical energy in the form of alternating current (AC) output, and, direct current (DC) output, respectively; the AC output being fed into an external circuit, and the DC output being fed back into the electricity generating system for energising a capacitor bank; and wherein the capacitor bank is electrically connectable to the variable speed drive and thereby the electrically driven motor, for supplying electrical energy for driving the electrically driven motor. The AC output may be utilised as a source for providing electricity to a load and/or external circuit.

The electricity generating system may further include an automatic voltage controller for providing a regulated direct current to the capacitor bank.

The electricity generating system may further include an inverter for converting direct current from the capacitor bank into alternating current for driving the electrically driven motor.

The electrically driven motor and the alternator may be operatively interconnected by a shaft extending thereinbetween.

The electrically driven motor may be a single phase AC motor.

The electrically driven motor may be a three phase AC motor.

The alternator may be a single-phase unit.

The alternator may be a three-phase unit.

The variable frequency drive coupled to the electrically driven motor adjust the speed of the motor as dictated by the specifications of the alternator.

The shaft may include rotational friction reduction elements in the form of one or more magnetic bearings, which magnetic bearings may be selected from any one or more of the groups consisting of passive magnetic bearings (PMB), and active magnetic bearings (AMB).

In this form of the invention a magnetic bearing controller (MBC) may be included for controlling the active magnetic bearing.

The electricity generating system may include a variable speed drive for controlling the speed of the electrically driven motor.

The capacitor bank may take the form of a plurality of capacitor banks coupled in series and/or parallel.

The capacitor bank may comprise a plurality of supercapacitors. In another form of the invention the alternator may yield AC output only in the absence of any DC output, wherein a portion of the AC output is fed into an external circuit while another portion of the AC output is fed back into the electricity generating system for driving the system.

In this form of the invention the electricity generating system may include a converter located downstream the alternator for converting AC output received form the alternator into DC output for energising the capacitor bank.

The converter in turn may include several electronic devices such as bridge rectifiers, diodes, transformers, and maximum power point tracker devices (MPPT).

The output voltage of the AC-DC converter may be between 10- and 250-volt direct current.

The output voltage may be determined by the design parameters of the electricity generating system and may be further dictated by the voltage and amperage required to energise the capacitor bank.

In yet a further form of the invention the electricity generating system may include a switching mechanism for allowing only a portion of the plurality of capacitor banks to energise the system while the other portion is being recharged by the alternator and not connected for energising the system.

The switching mechanism may include a programmable logic controller (PLC) configured to measure state of charge (SOC) of each of the capacitor banks. Once the minimum voltage threshold/SOC is reached for the particular capacitor bank, electrical current will be diverted to the other for recharging the subject capacitor bank while the other recharged capacitor bank energises the system.

In this manner a continuous supply of electrical energy is available for energising the system for driving the electrically driven motor.

In this form of the invention the alternator may yield AC output only in the absence of any DC output, a portion of the AC output being fed into an external circuit and another portion fed back into the system energising the system. In this form of the invention the electricity generating system may include a battery charger located in between the alternator and the capacitor bank, the battery charger further being connected to an AC output of the alternator.

The system may further include a direct current (DC) contactor located in between the battery charger and the capacitor bank for switching current supply between the plurality of capacitor banks, and, an alternating current (AC) contactor located in between the capacitor banks and inverter.

The PLC may be connected to each of the plurality of capacitor banks to measure the state of charge (SOC) of each.

Switching of electricity supply towards each of the plurality capacitor banks is facilitated by the PLC upon activation and, deactivation of the DC contactor and AC contactor, respectively, based in the SOC setting of each of the capacitor banks.

Once the minimum voltage threshold /SOC is reached for one of the capacitor banks supplying electrical energy to the system, the PLC will electrically change the state of the DC contactor and AC contactor, respectively, for switching electricity to be supplied from the other capacitor bank while the former capacitor bank is removed out of the system for recharging. In this manner a continuous supply of electrical current is provided by the plurality of capacitor banks for energising the system.

The PLC will on a continuous basis switch between each of the plurality of capacitor banks based on the minimum voltage threshold/SOC setting of each of the capacitor bank.

The electricity generating system may further include a plurality of hybrid inverters, each connected to each of the capacitor banks and located downstream thereof.

In this form of the invention a pair of AC contactors may be provided and included and interconnecting the plurality of hybrid inverters and a PLC, respectively.

The PLC may be programmed to receive a continuous digital/analogue signal from each of the plurality of capacitors banks and change the state of each of the AC contactors to direct charge from either of the capacitor banks into the system while the other is being charged. Brief Description of the Drawings

The invention will now be described by way of the following, non-limiting example with reference to the accompanying drawings.

In the drawings:-

Figure 1 is a schematic of an electrical circuitry in accordance with a first embodiment;

Figures 2 to 4 are schematic of an electrical circuitry in accordance with a second embodiment;

Figure 5 is a schematic depicting an alternative arrangement of the shaft connection; and

Figures 6 and 7 are schematics of an electrical circuitry in accordance with a third embodiment, in accordance with the invention.

Detailed description of the drawings

The invention will now be described in more detail wherein an electricity generating system in accordance with an embodiment of the invention is depicted by reference numeral 10.

Figure 1 depicts an electrically driven motor 12, the speed of which is controlled by a variable frequency drive 24, the electrically driven motor 12 being operatively coupled to an alternator 141 , the alternator 14 further being configured yield electrical energy in the form of alternating current (AC) output, and, direct current (DC) output, respectively, the AC output being fed into an external circuit, and the DC output being fed back into the electricity generating system 10 for energising a capacitor bank 16; and wherein the capacitor bank 16 is electrically connectable to the variable frequency drive 24 and thereby the electrically driven motor 12, for supplying electrical energy for driving the electrically driven motor.

The AC output will typically be utilised as electrical source for providing electricity to a load and/or external circuit such as a household circuitry, or the like. The electricity generating system 10 further include an automatic voltage controller 18 regulating direct current received from the alternator 14 to the capacitor bank 16.

The electricity generating system 10 can further include an inverter 20 for converting direct current from the capacitor bank 16 into alternating current for driving the electrically driven motor 12.

The electrically driven motor 12 and the alternator 14 can be operatively interconnected by a shaft 22 extending thereinbetween.

The electrically driven motor 12 can be in the form of a single-phase AC motor or three-phase AC motor. Speed of the electrically driven motor is further regulated by the inclusion of the variable frequency drive 24.

The alternator 14 in turn can be a single-phase unit, or, a three-phase unit.

Figures 2 to 4 depict a second embodiment 110 of the electricity generating system which includes an electrically driven motor 112 for driving alternator 114, where alternator 114 is configured to yield AC current only, in the absence of DC current, a portion of the AC current being diverted back into the system 110 and another portion of which being diverted into an external load.

In this embodiment an AC/DC converter 128 is provided for converting AC current received from the alternator 114 to DC current for energising capacitor bank 116.

The AC/DC converter 128 in turn can include several electronic devices such as bridge rectifiers, diodes, transformers, and maximum power point tracker devices (MPPT).

The output voltage of the AC-DC converter can be between 10- and 250-volt direct current.

The output voltage can be determined by the design parameters of the electricity generating system 110 and may be further dictated by the voltage and amperage required to energise the capacitor bank 116. The capacitor bank 116 can take the form of a plurality of capacitor banks coupled in series and/or parallel.

The capacitor bank 116 can comprise a plurality of supercapacitors.

Figure 5 illustrates integral connection between the alternator 14 and 114, and electrically driven motor 12 and 112 by shaft 18, and 118.

Figures 6 and 7 depict a third embodiment of the electricity generating system 210 comprising a switching mechanism where the switching mechanism is configured to allow only a portion of the plurality of capacitor banks to energise the system while the other portion is being recharged.

The switching mechanism comprise a programmable logic controller (PLC) 230 configured to measure state of charge (SOC) of each of the capacitors 216.1 and 216.2, comprising the capacitor bank 216.

In use, once the minimum voltage threshold/SOC is reached for a particular capacitor bank 216.1 or 216.2, electrical current is diverted to the other capacitor bank for recharging the subject capacitor bank while the recharged capacitor bank is linked back into the system 210 for energising the system 210.

In this manner a continuous supply of electrical energy is available for energising the system 210 for driving the electrically driven motor 212.

In this form of the invention the alternator 214 can be configured to yield AC output only in the absence of any DC output, a portion of the AC output being fed into an external circuit and another portion fed back into the system energising the system 210.

Figure 6 depicts the electricity generating system 210 further including a battery charger 232 located in-between the alternator 214 and the capacitor bank 216, the battery charger 232 further being connected to an AC output of the alternator 214.

The system 210 further include a direct current (DC) contactor 234 located inbetween the battery charger 232 and the capacitor bank 216 for switching current supply towards a portion of the plurality of capacitor banks 216, and an alternating current (AC) contactor 236, located in-between the capacitor bank 216 and inverter 220.

The PLC 230 is further connected to each of the plurality of capacitor banks 216.1 and 216.2 and set up to measure the state of charge (SOC) of each of the capacitor banks 261.2 and 216.2

Switching of electricity supply towards each of the plurality capacitor banks 216.1 and 216.2 is facilitated by the PLC 230 upon activation and, deactivation of the DC contactor 234 and AC contactor 236, respectively, based in the SOC setting of each of the capacitor banks 216.1 and 216.2.

Once the minimum voltage threshold /SOC is reached for one of the capacitor banks

216.1 and 216.2 respectively, the PLC 230 will electrically change the state of the DC contactor 234 and AC contactor 236, respectively, for switching electricity to be supplied from the other capacitor bank while the former capacitor bank is electrically removed out of the system 210 for recharging. In this manner a continuous supply of electrical current is provided by the plurality of capacitor banks 216.1 and 216.2 for energising the electricity generating system 210.

Figure 7 depicts another configuration of the switching mechanism which includes a plurality of hybrid inverters 238.1 and 238.2, each connected to each of the capacitor banks 216.1 and 216.2, the capacitor banks 216.1 and 216.2 located downstream the inverters 238.1 and 238.2.

In this form of the invention a pair of AC contactors 240.1 and 240.2 is further included and arranged to interconnect the plurality of hybrid inverters 238.1 and

238.2, and the PLC 230, respectively.

In this configuration the PLC 230 will be programmed to receive a continuous digital/analogue signal from each of the plurality of capacitors banks 216.1 and

216.2, respectively, and change the state of each of the AC contactors 240.1 and

240.2, respectively, to direct charge from either of the capacitor banks 216.1 and

216.2 into the system 210 while the charged capacitor bank 216.2 or 216.2, is linked into the circuitry for energising the system. The electrically driven motor 12, 112 and 212, and the electrical alternator 14, 114, and 214, as depicted in the figures are readily available (off-the-shelf) items. These units are normally supplied with either roller bearings or ball bearings that might be arranged in either single or double configurations.

Known drawbacks of using bearings in these components are the losses generated through friction. Friction can further be broken down to drag and heat generation. Bearings are the number one cause of electric motor failure and requires continuous maintenance and lubrication. By using magnetic bearings 126, see figures 2 to 4, rotating components can be made significantly more reliable and efficient through completely removing friction from the equation.

Magnetic bearings have the advantage that there is no contact between the stationary and rotating parts of the component. This results in no friction between the components making both the electrical motor 12, 112 and 212, and the electrical alternator 14, 114 and 214, more efficient and reliable. Magnetic bearing technologies are available as PMBs (Passive Magnetic Bearings) or AMBs (Active Magnetic Bearings). With PMBs both the inner and outer rings are made from permanent magnets which means that they are active all the time, and with AMBs the inner and/or outer rings get their magnetism from electromagnets activated by a voltage induced into its coils. For AMBs to work it requires an MBC Magnetic Bearing Controller 129, see figure 4.

Electricity generating system 110 as depicted in figure 3, the shaft 122 includes one or more passive magnetic bearings (PMB) 127. This electricity generating system 110 further includes the electrical motor 112, alternator 114, capacitor bank 116, shaft 122, AC/DC variable speed drive 124, and inverter 120.

In figure 4 electricity generating system 110 is depicted wherein the shaft 122 includes one or more active magnetic bearings 126. In this embodiment a magnetic bearing controller (MBC) 129 is included for controlling the active magnetic bearing 126. This electricity generating system further includes the electrically driven motor 112, alternator 114, capacitor bank 116, shaft 122, AC/DC converter 128, variable speed drive 124, and inverter 120.

The Applicant considers the invention advantageous in that an electricity generating and supply system is depicted which is effectively driven by an electrically driven motor for driving an alternator which provides AC and/or DC output. The electrical energy storage banks in the form of supercapacitors are further energised by a portion of the energy output of the alternator which energy is used to drive the electrically driven motor. The system further delivers clean and silent electrical energy output in the absence of an internal combustion engine.