Patent Description:
Generally, electricity distribution is the final stage in the delivery of electricity to customers. In a typical electrical distribution system (e.g., electrical sub-stations, power lines, pole-mounted transformers, distribution wiring, electric energy meters, etc.), the electrical distribution system carries the electricity generated from a transmission system (e.g., power plant, transformers, high voltage transmission lines, etc.) and supplies the electricity to customers via an electric meter.

In industrial applications, there is a wide range of applicable power supplies. For example, in the U. , industrial application power supplies range from <NUM> volts (V) to <NUM> V. Approximately ninety-seven percent of these applications fall within the 120V to 277V range. Therefore, only approximately three percent of the industrial applications require <NUM> V Delta configurations. Additionally, systems for oil and irrigation applications require <NUM> V with substantial transients due to long transmission lines and motor starts or stops. In Canada, industrial application power supplies require <NUM> V. There are also a small percentage of applications that require 57V to 120V. It is cost prohibitive to qualify a new meter for each specific power supply requirement at these lower volumes. Further, it may require extensive development time to qualify these new meters.

<CIT> concerns a metering device including a standard AC energy meter and a conversion circuit. The conversion circuit measures the voltages and currents of an installation incompatible with the functional characteristics of the meter, and supplies the meter with AC voltages and currents of values in compliance with the specifications of the meter. In particular, the conversion circuit uses the measured voltages and currents to modulate an independently generated AC signal and provides the modulated signal to the meter.

<CIT> and <CIT> concern electrical energy meters, and <CIT> concerns a method for monitoring electrical characteristics on an electronic circuit board.

The present invention provides a system comprising an electric meter and a voltage-modifying device as defined in appended claim <NUM>.

It is noted that the drawings of the invention are not to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention.

Aspects of the invention provide for qualifying a new meter with specific power supply requirements. In one embodiment, aspects of the invention include a system, including: an electric meter having a housing; and a voltage-modifying device connected to the electric meter for modifying a received voltage, such that the electric meter operates in accordance with a predetermined power supply requirement, wherein the voltage-modifying device is located within the electric meter housing or external to the electric meter housing.

For example, as mentioned above, power supplies for industrial applications range from 120V to 480V. However, only approximately ninety-seven percent of these applications require 120V to 277V. It is more cost effective to design a 120V to 277V power supply instead of a 120V to 480V power supply The voltage-modifying device, according to aspects of the invention, enables a 120V to 277V power supply to be used for applications from 120V to 480V. Further, in oil and irrigation applications that require 480V Delta systems, overvoltage can often occur, which results in voltage transient problems. The voltage-modifying device described herein provides protection against high voltage transients. Therefore, it is not required to fully re-qualify a new meter for a specific power supply requirement of each application.

Turning to <FIG> and <FIG>, a schematic diagram of a system <NUM> according to aspects of the invention is shown. A power supply <NUM> may be connected to a voltage-modifying device <NUM>. Voltage-modifying device <NUM> may be connected to an electronic board (not shown) of an electric meter <NUM>. Although not shown, the electric meter <NUM> includes a housing. As will be described below, the voltage-modifying device <NUM> enables the electric meter <NUM> to operate in accordance with a predetermined power supply requirement. Although it is not shown, it is understood that the voltage-modifying device <NUM> may be located within the housing of the electric meter <NUM> or external to the electric meter <NUM>.

System <NUM> will be described with respect to a three-phase power supply system. Accordingly, three lines (i.e., phases) connect the power supply <NUM> to the voltage-modifying device <NUM>. An optional neutral line <NUM> is shown, that includes a resistor <NUM>. An additional line (an adapter terminal) <NUM> connects the voltage-modifying device <NUM> to the electric meter <NUM>. As will be described herein, the adapter terminal <NUM> provides voltage feedback and supply separation for the meter <NUM>.

Although system <NUM>, as described herein, is applied to a three-phase power supply system, it is understood that the applications of system <NUM> may be applied to any now known or later developed power supply system.

Turning now to <FIG>, a more detailed schematic diagram of the voltage-modifying device <NUM> of system <NUM> is shown. System <NUM>, and voltage-modifying device <NUM>, is show including a first phase <NUM>, a second phase <NUM>, and a third phase <NUM>. There may be an additional wire for neutral; however, the neutral wire has been omitted for clarity purposes. An adapter terminal <NUM> connects the voltage-modifying device <NUM> to the electric meter <NUM> (<FIG>). As will be described herein, the adapter terminal <NUM> provides voltage feedback and supply separation for the meter <NUM>.

As seen in <FIG>, voltage-modifying device <NUM> includes a Surge protection circuit <NUM> connected to first phase <NUM> and second phase <NUM>. Surge protection circuit <NUM> includes a surge resistor <NUM> coupled in series with at least one varistor <NUM>. <FIG> shows Surge protection circuit <NUM> including two varistors <NUM>; however, it is understood that Surge protection circuit <NUM> may include any number of varistors <NUM>. Varistor <NUM> may include a metal oxide varistor, or any now known or later developed type of varistor. Varistor <NUM> is used to protect against excess transient voltages by shunting the current created by the high voltage away from other parts of the circuit.

Voltage-modifying device <NUM> includes an electromagnetic interference (EMI) filtering device <NUM> coupled in series with the Surge protection circuit <NUM>. EMI is a disturbance that can affect the operation of the electrical circuitry within the voltage-modifying device <NUM> by interrupting, obstructing, or limiting the effect performance of the circuit. Examples of EMI filtering devices that may be used include a common mode choke, an x-capacitor, or an inductor and capacitor ("LC") filter. However, other EMI filtering devices, as known in the art, may be used.

In this embodiment of <FIG>, voltage-modifying device <NUM> includes an overvoltage protection module <NUM>. Overvoltage protection module <NUM> is configured to turn off power to the electric meter <NUM> (<FIG>) in response to receiving a voltage that exceeds the predetermined power supply requirement. For example, a <NUM> V-<NUM> V meter may turn off the power supply voltage to the switch power mode in order to protect it when there is a voltage more than 480V.

An overvoltage detection circuit <NUM>, within the overvoltage protection module <NUM>, detects when an overvoltage occurs. In response to an overvoltage occurring, the overvoltage detection circuit <NUM> turns on the overvoltage protection module <NUM>. In the embodiment shown in <FIG>, the overvoltage protection module <NUM> includes a diode <NUM> electrically connected in series with a varistor <NUM>, a diode <NUM>, and a metal-oxide-semiconductor field-effect transistor (MOSFET) <NUM>, which are electrically connected in parallel. The overvoltage protection module <NUM> also includes a capacitor <NUM>. However, it is understood that overvoltage protection module may include any devices necessary to turn off power to the electric meter (<FIG>), in response to an overvoltage that exceeds the predetermined power supply requirement.

At least one additional resistor <NUM> may be provided for voltage feedback. For example, an additional resistor <NUM> is shown in <FIG> to provide voltage feedback of the first phase <NUM> to the meter <NUM> (<FIG>) through the adapter terminal <NUM>. This additional resistor <NUM> also provides a separate terminal <NUM> off of the first phase <NUM> in order to provide supply separation. A second additional resistor <NUM> may also be provided for voltage feedback and supply separation for the third phase <NUM>. In this embodiment, the second phase <NUM> passes through EMI filtering device <NUM> and is used as a reference potential. This is often the case for a half-wave rectification system.

Turning now to <FIG>, a detailed schematic diagram of an alternative embodiment of the voltage-modifying device <NUM> in <FIG> is shown. In this embodiment, a third additional resistor <NUM> is provided for the second phase <NUM>. As with the first additional resistor <NUM> for the first phase <NUM> and the second additional resistor <NUM> for the third phase <NUM>, this third additional resistor <NUM> provides voltage feedback and supply separation for the second phase <NUM>. In this embodiment, the second phase <NUM> passes through the EMI filtering device <NUM>.

Turning now to <FIG>, a detailed schematic diagram of an alternative embodiment of the voltage-modifying device <NUM> is shown. In this embodiment, the voltage-modifying device <NUM> includes a high voltage module <NUM> (or step-down circuit) coupled in series with the EMI filtering device <NUM>. High voltage module <NUM> is configured to decrease a received voltage in response to the receiving a voltage that exceeds the predetermined power supply requirement. For example, the meter may be a <NUM> V-<NUM> V meter and the voltage-modifying device <NUM> is configured to so that meter is compatible with higher voltage lines, such as, <NUM> V lines.

A buck control circuit <NUM>, within the high voltage module <NUM>, regulates and reduces the voltage to a voltage level that is compatible with the meter <NUM>. For example, for a 120V-277V meter that is connected to 600V lines, the buck control circuit <NUM>, within the voltage-modifying device <NUM>, will reduce the voltage to a voltage that is compatible with the 120V-277V meter. As known to one of ordinary skill in the art, the buck converter includes two switches (a diode <NUM> and a switch <NUM>), an inductor <NUM>, and a capacitor <NUM>. The two switches <NUM>, <NUM> alternate between charging the inductor <NUM> and discharging the inductor <NUM> to decrease the voltage. It is understood that other configurations of a buck converter, as known in the art, may be used in high voltage module <NUM>.

As seen in <FIG>, the high voltage module <NUM> may include other electrical circuit components, such as an additional diode <NUM> and an additional capacitor <NUM>. These may be known as half-wave rectification elements. However, it is understood that the high voltage module <NUM> may include any devices necessary to decrease the voltage to the electric meter (<FIG>), in response to a voltage that exceeds the predetermined power supply requirement.

Similar to the embodiment shown in <FIG>, at least one additional resistor <NUM> may be provided for voltage feedback. For example, an additional resistor <NUM> is shown in <FIG> to provide voltage feedback of the first phase <NUM> to the meter <NUM> (<FIG>) through the adapter terminal <NUM>. The additional resistor <NUM> also increases the voltage divider ratio of the voltage feedback. This additional resistor <NUM> also provides a separate terminal <NUM> off of the first phase <NUM> in order to provide supply separation. A second additional resistor <NUM> may also be provided for voltage feedback and supply separation for the third phase <NUM>. In this embodiment, the second phase <NUM> does not pass through the EMI filtering device <NUM>.

Turning now to <FIG>, a detailed schematic diagram of an alternative embodiment of the voltage-modifying device <NUM> is shown. In this embodiment, the voltage-modifying device <NUM> includes a low voltage module <NUM> (or a step-up circuit), such as a boost converter, coupled in series with the EMI filtering device <NUM>. Low voltage module <NUM> is configured to increase a received voltage in response to the receiving a voltage that does not meet the predetermined power supply requirement. For example, substation units may require <NUM> V-<NUM> V power supplies, which would make the substation units not compatible with a 120V-277V meter.

A control circuit <NUM>, within the low voltage module <NUM>, regulates an input supply voltage from the power supply <NUM> (<FIG>) to deliver a voltage that is compatible with a predetermined power supply requirement of the meter <NUM> (<FIG>). The components within the low voltage module <NUM> make up a boost converter that increases the voltage from the power supply <NUM> (<FIG>) to the predetermined power supply requirement of the meter <NUM> (<FIG>). As known to one of ordinary skill in the art, the boost converter includes two switches (a switch <NUM> and a diode <NUM>), an inductor <NUM>, and a capacitor <NUM>. The two switches <NUM>, <NUM> alternate between charging the inductor <NUM> and discharging the inductor <NUM> to increase the voltage. It is understood that other configurations of a boost converter, as known in the art, may be used in low voltage module <NUM>.

As seen in <FIG>, the low voltage module <NUM> may include other electrical circuit components, such as an additional diode <NUM> and an additional capacitor <NUM>. These may be known as half-wave rectification elements. However, it is understood that the low voltage module <NUM> may include any devices necessary to increase the voltage to the electric meter (<FIG>), in response to a voltage that does not meet the predetermined power supply requirement.

Although not shown in the figures, it is understood that the voltage-modifying device <NUM> may include a combination of the embodiment shown in <FIG> and the embodiment shown in <FIG>. That is, the voltage-modifying device <NUM> may include a buckboost converter or a sepic converter, which can increase or decrease the received voltage to the predetermined power supply requirement of the meter <NUM>.

Claim 1:
A system (<NUM>), comprising:
an electric meter (<NUM>) having a housing (<NUM>), wherein the electric meter (<NUM>) includes an adapter terminal (<NUM>); and
a voltage-modifying device (<NUM>) having an input configured to be connected to a three-phase power supply (<NUM>) and a power supply output connected to the electric meter (<NUM>), the voltage-modifying device (<NUM>) being configured for modifying a received voltage, such that the electric meter (<NUM>) operates in accordance with a predetermined power supply (<NUM>) requirement, wherein the voltage-modifying device (<NUM>) is located within the electric meter (<NUM>) housing (<NUM>) or external thereto, and wherein the voltage-modifying device (<NUM>) also connects to the electric meter (<NUM>) via the adapter terminal (<NUM>), characterised in that the adapter terminal (<NUM>) is provided with at least one resistor (<NUM>) configured for providing voltage feedback of the three-phase power supply (<NUM>) to the electric meter (<NUM>) and supply separation for the electric meter (<NUM>).