A resonant power transfer system includes resonant circuitry (26) including an inductor coil (59) and a resonant capacitor (51) coupled to a first terminal (27) of the inductor coil, wherein the inductor coil and the resonant capacitor resonate to produce an excitation signal (I.sub.S) and a state variable signal (V.sub.CS1). Sub-sampling circuitry (30) samples first and second points of the state variable signal at a rate which is substantially less than the RF frequency of the state variable signal. Information recovery circuitry (32) produces a state variable parameter signal representing a parameter (A) of the state variable signal from information in the first and second sampled points. Control circuitry (38) produces a first control signal in response to the state variable parameter signal. Detection and optimization circuitry (41) produces a second control signal in response to the state variable parameter signal. Voltage regulation circuitry (45) produces a regulated supply voltage in response to the first control signal. Switching inverter circuitry produces the excitation signal in response to the regulated supply voltage and the second control signal.

A resonant power transfer system includes resonant circuitry (26) including an inductor coil (59) and a resonant capacitor (51) coupled to a first terminal (27) of the inductor coil, wherein the inductor coil and the resonant capacitor resonate to produce an excitation signal (I.sub.S) and a state variable signal (V.sub.CS1). Sub-sampling circuitry (30) samples first and second points of the state variable signal at a rate which is substantially less than the RF frequency of the state variable signal. Information recovery circuitry (32) produces a state variable parameter signal representing a parameter (A) of the state variable signal from information in the first and second sampled points. Control circuitry (38) produces a first control signal in response to the state variable parameter signal. Detection and optimization circuitry (41) produces a second control signal in response to the state variable parameter signal. Voltage regulation circuitry (45) produces a regulated supply voltage in response to the first control signal. Switching inverter circuitry produces the excitation signal in response to the regulated supply voltage and the second control signal.

An energy harvesting device (CTH) installed in an electrical distribution system (EDS) for powering ancillary electrical devices (AD) used in the distribution system. The device includes a first voltage regulator circuit (CC) configured to produce a voltage matched to a power curve of a current transformer (CT) to which the device is electrically coupled. The device also includes a second and separate voltage regulator circuit (SVR) which continuously operates to maximize the amount of electrical energy recovered from the current transformer.

An energy harvesting device (CTH) installed in an electrical distribution system (EDS) for powering ancillary electrical devices (AD) used in the distribution system. The device includes a first voltage regulator circuit (CC) configured to produce a voltage matched to a power curve of a current transformer (CT) to which the device is electrically coupled. The device also includes a second and separate voltage regulator circuit (SVR) which continuously operates to maximize the amount of electrical energy recovered from the current transformer.

An alternating current (AC) mitigation system reduces undesired AC current induced in a pipe section by the electromagnet field of a nearby electrical utility power line. An active feedback system processes samples of the undesired AC signal from a current sensor located at the pipe section. A feedback controller generates a current compensation signal that is applied to the pipe section at a current coupler to cancel out the undesired AC signal. Corrosion of the pipe section caused by the undesired AC current may be reduced or eliminated.

An alternating current (AC) mitigation system reduces undesired AC current induced in a pipe section by the electromagnet field of a nearby electrical utility power line. An active feedback system processes samples of the undesired AC signal from a current sensor located at the pipe section. A feedback controller generates a current compensation signal that is applied to the pipe section at a current coupler to cancel out the undesired AC signal. Corrosion of the pipe section caused by the undesired AC current may be reduced or eliminated.

In various embodiments, a transformer provides a voltage. A regulating circuit coupled to the transformer regulates the voltage to provide either a first voltage or a second voltage that is independent of the first voltage.

The invention generally relates to methods and circuits for controlling switching of parallel coupled power semiconductor switching devices (3), for example for use in a power converter. In an example, there is provided a circuit for controlling switching of parallel coupled power semiconductor switching devices (3), the circuit comprising: a plurality of drive modules (2), each said module for controlling a said power semiconductor switching device (3); control circuitry to transmit switch command signals to the modules, each said switch command signal to trigger a said drive module to control a said power semiconductor switching device to switch state; and voltage isolation between the drive modules and the control circuitry, wherein each said drive module for controlling a said device comprises: timing circuitry (22) to compare a switching delay of the device and a reference delay, wherein said switching delay is a time interval between detecting a said switching command signal at the drive module and switching of the device in accordance with the detected switching command signal; and delay circuitry (21) to provide a controllable delay to delay a said triggering by a said switching command signal received at the module subsequent to the detected switching command signal, the delay circuitry configured to control the controllable delay according to a result of said comparison of said switching delay of the device, to thereby reduce a time difference between the reference delay and a said switching delay of the device switching in accordance with the subsequent switching command signal.

A system and method for optimizing cable size and flexibility for a pool or spa installation is provided. The system includes an inductive power coupling having first and second power couplings. The inductive power coupling transforms a first voltage level provided by the cable to a second voltage level suitable for usage by the pool or spa component and compensates for a voltage loss associated with the cable allowing the cable to have a size and flexibility suitable for installation in a pipe or conduit. The first power coupling is in electrical communication with a power supply via a cable and the second power coupling is in electrical communication with a pool or spa component. The first power coupling inductively transmits received power from the power supply via the cable to the second power coupling. The second power coupling inductively transmits the received power to the pool or spa component.

A system and method for optimizing cable size and flexibility for a pool or spa installation is provided. The system includes an inductive power coupling having first and second power couplings. The inductive power coupling transforms a first voltage level provided by the cable to a second voltage level suitable for usage by the pool or spa component and compensates for a voltage loss associated with the cable allowing the cable to have a size and flexibility suitable for installation in a pipe or conduit. The first power coupling is in electrical communication with a power supply via a cable and the second power coupling is in electrical communication with a pool or spa component. The first power coupling inductively transmits received power from the power supply via the cable to the second power coupling. The second power coupling inductively transmits the received power to the pool or spa component.