Circulating load apparatus

A circulating load apparatus for loading a power supply having a power input terminal, a power output terminal and a power return terminal, the power supply having an internal impedance and being characterized to provide an output voltage at the power output terminal with respect to the power return terminal, the output voltage of the power supply being controlled to be substantially identical in amplitude to the network voltage of a network source, provided at a network source terminal with respect to a source return terminal, the power return terminal being coupled to the source return terminal, the power supply power input terminal being coupled to the network source terminal to be powered by voltage and current from said network source terminal, the circulating load apparatus comprising:

• a voltage source for supplying a voltage between a first and second terminal, the voltage source being connected in series between the network source terminal and the power supply power output terminal, the voltage source is coupled to be powered by voltage and current from said network source;
• the output voltage of the power supply and the voltage source adding to provide output power to the network source;
• adjusting means for adjusting the amplitude of the voltage of the voltage source to position the output current of the power supply within a predetermined range and wherein the adjusting means further comprises an ammeter connected in series with the power supply and the voltage source external to the network source between the network source terminal and the source return terminal;
• the voltage of the voltage source being adjustable by an operator to position the output current indicated by the ammeter to be within a predetermined range.

A circulating load apparatus for loading a power supply, the power supply having a dc output voltage and a dc input voltage, a power input terminal, a power output terminal and a power return terminal, the power supply having an internal impedance and being characterized to provide an output voltage at the power output terminal with respect to the power return terminal, the output voltage of the power supply being controlled to be substantially identical in amplitude to the network voltage of a network source, provided at a network source terminal with respect to a source return terminal, the power return terminal being coupled to the source return terminal, the power supply power input terminal being coupled to the network source terminal to be powered by voltage and current from said network source terminal, the circulating load apparatus comprising:

• a voltage source for supplying a voltage between a first and second terminal, the voltage source being connected in series between the network source terminal and the power supply power output terminal;
• the output voltage of the power supply and the voltage source adding to provide output power to the network source;
• and wherein, the voltage source is an isolated dc voltage source coupled to be powered by voltage and current from said network source and having an output voltage that is adjusted to obtain the required output current and wherein the network source is a dc voltage source;
• adjusting means for adjusting the amplitude of the voltage of the voltage source to position the output current of the power supply within a predetermined range.

A circulating load apparatus for loading a sinusoidal power supply having a power input terminal, a power output terminal and a power return terminal, the power supply having an internal impedance and operable to provide a sinusoidal output voltage at the power output terminal with respect to the power return terminal, the sinusoidal output voltage of the power supply being controlled to be substantially identical in amplitude and frequency to the sinusoidal source voltage from a network source, provided at a network source terminal with respect to a source return terminal, the power return terminal being coupled to the source return terminal, the power supply power input terminal being coupled to the network source terminal to be powered by voltage and current from the network source terminal, the circulating load apparatus comprising:

• a voltage source for supplying a sinusoidal amplitude and phase adjustable voltage between a first and second terminal, the frequency of the amplitude and phase adjustable voltage being equal to the frequency of the sinusoidal output voltage of the power supply, the output voltage of the voltage source being connected in series between the network source terminal and the power supply power output terminal;
• the output voltage of the power supply and the output voltage of the voltage source adding to provide output power to the network source;
• adjusting means for adjusting the amplitude and phase of the amplitude and phase adjustable sinusoidal voltage of the voltage source to position the output current of the power supply within a predetermined range.

A circulating load apparatus for loading a sinusoidal power supply having a power input terminal a power output terminal and a power return terminal, the power supply having an internal impedance and being characterized to provide a sinusoidal output voltage at the power output terminal with respect to the power return terminal, the sinusoidal output voltage of the power supply being controlled to be substantially identical in amplitude and frequency to the sinusoidal source voltage from a network source provided at a network source terminal with respect to a source return terminal, and wherein the network source further comprises:

• a first, second and third voltage source for providing a first, second and third source voltages with respect to the source return terminal, the second source voltage trailing the first source voltage by substantially 120 degrees and the third source voltage trailing the second source voltage by substantially 120 degrees, each respective source voltage being substantially equal in amplitude, the power return terminal being coupled to the source return terminal the power supply power input terminal being coupled to the network source terminal to be powered by voltage and current from the network source terminal, the circulating load apparatus comprising:
• a voltage source for supplying a sinusoidal amplitude and phase adjustable voltage between a first and second terminal, the frequency of the amplitude and phase adjustable voltage being equal to the frequency of the sinusoidal output voltage of the power supply, the output voltage of the voltage source being connected in series between the network source terminal and the power supply power output terminal;
• the output voltage of the power supply and the output voltage of the voltage source adding to provide output power to the network source;
• adjusting means for adjusting the amplitude and phase of the amplitude and phase adjustable sinusoidal voltage of the voltage source to position the output current of the power supply within a predetermined range;
• the adjusting means further comprising:
• a first adjustable transformer driven by the first source voltage with respect to the source return terminal for providing an adjustable reference voltage, and
• a second adjustable transformer driven by the second source voltage with respect to the third source voltage for providing an adjustable quadrature voltage, and wherein,
• the voltage source is coupled to be powered by said adjustable reference voltage and the adjustable quadrature voltage.

A circulating load apparatus for loading a sinusoidal power supply having a power input terminal, a power output terminal and a power return terminal, the power supply having an internal impedance and operable to provide a sinusoidal output voltage at the power output terminal with respect to the power return terminal, the sinusoidal output voltage of the power supply being controlled to be substantially identical in amplitude and frequency to a sinusoidal source voltage from a network source, provided at a network source terminal with respect to a source return terminal, the network source having a first, second and third voltage source for providing a first, second and third source voltages with respect to the source return terminal, the second source voltage trailing the first source voltage by substantially 120 degrees and the third source voltage trailing the second source voltage by substantially 120 degrees, each respective source voltage being substantially equal in amplitude, the power return terminal being coupled to the source return terminal, the power input terminal being coupled to the network source terminal to be powered by voltage and current from the network source, the circulating load apparatus comprising:

• a first adjustable transformer driven by the first source voltage with respect to the source return terminal for providing an adjustable reference voltage, and
• a second adjustable transformer driven by the second source voltage with respect to the third source voltage for providing an adjustable quadrature voltage,
• an isolation transformer having a first primary winding driven by the adjustable reference voltage, a second primary winding driven by the adjustable quadrature voltage, and a secondary winding connected with the power supply and network source, the adjustable reference voltage and the adjustable quadrature voltage being adjusted to provide a scaled sum voltage across the isolation transformer secondary, the amplitudes of the adjustable reference voltage and the adjustable quadrature voltage being adjusted to adjust the scaled sum voltage to provide output power from the power supply to the network source.

A circulating load power saving process comprising the steps of:

• connecting an ac network source to provide an ac source voltage to the ac power input terminals of a plurality of ac to dc power supplies, each dc power supply having a primary conversion section that is dc isolated from a secondary conversion section, each secondary conversion section having a dc output voltage terminal and a dc return terminal;
• connecting the output terminals of separate secondary conversion sections of each respective ac to dc power supply in series to charge a capacitor to a dc service voltage equal to the sum of dc output voltages of the respective secondary conversion sections;
• connecting the input power terminals of a dc to ac converter to the dc service voltage to provide an ac output voltage having a frequency equal the frequency of the ac network source;
• and
• operating the ac to dc power supplies and the dc to ac converter to deliver a controlled level of ac power to the network source.