Abstract: There is provided a novel drape for covering surgical equipment, particularly but not exclusively for covering elongate surgical equipment which flexes during use, such as an endoscopic camera cable. The drape comprises a sleeve and a ring-shaped former. The ring-shaped former is arranged coaxially inside the sleeve, the majority of the latter being multiply folded over and carried on the ring-shaped former. The proximal region of the sleeve contacts the radially outer periphery of the ring-shaped former and it is overlaid with successive sleeve layers arising from repeated 180.degree. folds in the sleeve. Pulling the distal region of the sleeve away from the former causes orderly unfolding of the sleeve by relative sliding of the outermost layer over the adjacent layer.

Abstract: A wind turbine drives the squirrel-cage rotor of a capacitively excited induction generator. The amount of excitation is controlled in accordance with the output voltage of the stator and hence the speed of the wind turbine. The generating system is capable of operating at high efficiency over a wide speed range, since the electrical output frequency is allowed to vary with the rotor speed. The electrical power supplied by the induction generator is used for heating purposes within a nearby building.

Abstract: AC to DC converters used in high-voltage direct-current power transmission lines produce objectionable harmonics. The composite filter herein described is actively tuned for the eleventh and thirteenth harmonics in addition to providing a low impedance path for the higher order harmonics, thereby eliminating such undesired harmonics so that they will not be transmitted over power lines where they can cause telephone interference, undesired heating of electrical equipment and other difficulties.

Abstract: A power supply capable of transferring power at high current and voltage levels to a load which may be highly inductive. The power supply includes an inverter for receiving DC power and inverting it to an AC intermediate signal. The intermediate signal is rectified by a converter to provide a DC output voltage to a load. Commutation of the controlled rectifying devices within the inverter and converter are provided by capacitors connected across the output terminals of the inverter. The DC output voltage provided to the load is controlled by the frequency of the firing signals provided to the controlled rectifying devices within the inverter. A large energy storage inductor, which may be superconductive, is connected to the inverter and may be utilized to provided the pulses of power required by the load. A converter connected to an AC power system is provided to supply external power and to recharge the current flowing in the energy storage inductor.

Abstract: An active filtration system is described which may be particularly useful for filtering undesired harmonics of the fundamental AC frequency produced by AC to DC or DC to AC conversion. The filtration system of the invention produces currents of a phase, frequency and magnitude for injection into the AC system such that the undesired harmonic currents to be filtered sum with the injected currents giving a net zero current at the undesired harmonic frequency. The system can incorporate existing passive filtration elements and provides a high-impedance parallel-filtration network to prevent the filteration system from acting as a "sink" for the ambient harmonics generated elsewhere in the AC system. Because the frequency, phase and magnitude of the injected currents are controlled, the filter of the invention remains highly effective even when these quantities and the filter component values vary.