Abstract: Inductive power transfer across an extended gap (100) from a primary conductor (119) is provided by means of a resonant intermediate loop comprised of capacitor (118) with inductor (117) carrying a larger resonating current, that can in turn generate an inductive field to be collected by a pickup coil (120). This process and device find application in an electroluminescent advertising panel.

Abstract: Disclosed is inductive coupling of power to devices having negative resistances, such as gas-filled discharge lamps (fluorescent tubes, neon signs, and the like) from a primary inductive loop, using resonant conditioning of the power provided to the device. A “C” shaped inductor (202) around the loop and a resonating capacitor (406) in parallel with the inductor provide a current source to the lamp (403) from across the capacitor. The circuit is capable of first igniting a lamp using a higher voltage available when the Q of the unloaded circuit is high, then running the lamp or other device at a controlled current. The lamp current is substantially proportional to the primary inductive loop flux, and substantially independent of the lamp resistance. A second inductor (404) in series with the first though not itself a collector of flux acts as a current limit. Applications include lighting, displays (optionally isolated and dimmable), and production of ultraviolet radiation.

Abstract: Loosely coupled inductive power for charging batteries is rectified from a first power pickup winding and the resulting current source is connected to a battery unit. Each current source is controlled by shorting a second resonant winding. Battery banks may be charged using multiple isolated position-tolerant pickups independently controlled according to the condition of the connected battery unit and by overall commands communicated over an isolated link. The battery unit may be a single cell. In a self-stabilizing bank or monoblock a primary inductive conductor is energized using all the cells, individual cells are separately monitored by control means and any below-average cell can be individually charged from the inductive conductor, thus correcting between-cell variations. The charge in all cells within a bank can be held within 30% to 70% of full charge and prevented from drifting towards full or empty during repetitive charge and discharge times.

Abstract: An energy-efficient energizer for an electric fence for controlling livestock or the like, includes an output voltage sensor. By switching to extra storage capacitance and/or altering the charge voltage the energizer varies the duration of the output pulse and perhaps also the pulse voltage according to the sensed output, thus maintaining an effective livestock barrier and consuming high power only when required. Output pulses are about 8 kV (no load) down to 4 kV (wide range of loads). The control algorithm determines the capacitor charging time and initiates a charge sooner if a higher power pulse is to be delivered, so maintaining a constant pulse rate. The energizer includes a 12V DC power option and has a circuit for synthesizing a substantially unipolar pulse having low harmonic content.

Abstract: An electric induction motor can be given a kick start without excessive current drain on the supply by first connecting a unidirectional supply to a winding of the motor to build up a stationary rotor flux and then applying a starting current to another winding of the motor to produce a stator flux at an appropriate angle (between 0.degree. and 180.degree.) with the stationary rotor flux. Once the motor has begun accelerating the normal running supply can be connected. This starting current may be derived from a capacitance which is charged up during the period of establishing the stationary rotor flux.

Abstract: An inductively coupled power distribution system for moving vehicles, in which resonating primary circuits to distribute power for resonating secondary circuits to collect and use in an optimized manner. In order to have all circuits resonating at substantially the same frequency, devices which detect and adjust resonating components are used, such as a frequency drift compensator in which the present frequency is compared to a reference voltage and causes a driver to be ON or OFF accordingly. Switches are driven CLOSED or OPEN respectively and when CLOSED, supplementary capacitors are included with a main capacitor in a primary resonant circuit. Dithering or pulsed control provides a continuous control of resonance, as the system takes some milliseconds to respond.

Abstract: A flux concentrator 1300 for an inductive power transfer system is made up from rectangular fingers 1301 of ferrite material held in close contact by compression means to form a large shock resistant core. The fingers are positioned at right angles to a primary conductor 1312 to concentrate the horizontal component of the magnetic flux through the flux concentrator. The fingers include bridge sections 1309 adapted to support pick-up coil windings 1307. The flux concentrator is covered by a conducting sheet of aluminum 1311 on the side of the magnetic core far away from the source of magnetic flux.

Abstract: A circuit (700) for an electric fence energizer (examples are 6 or 24 Joule versions) which synthesizes a pulse having a raised cosine waveform at a first or bus voltage uses a ferrite-cored output transformer (701) to multiply the voltage of the pulse to the required level. A raised cosine waveform has a low harmonic content and little filtering of high-power pulses is required in order to minimize electromagnetic emissions. On closure of a switch (707) in series with an inductor (705) a first capacitor bank (703) commences charging a second smaller capacitor bank (704) in parallel with the output primary and after the peak of the pulse any remaining charge is dissipated in a resistor (708) with the aid of a saturable inductor (702), acting as a switch. The saturable inductor may be the output transformer itself for lower output energizers. The output exhibits little or any reversal of polarity when matched to its load. The circuit may also be useful for applications such as strobe flashers in aircraft.