U.S. Philips Corporation

Andreas C Van Veghel

Pieter Postma

Henk Houkes

Jacobus Crucq

A pulse-drive circuit for an electric motor in which the steep edges in the drive-signal are made to vary substantially stepwise, i.e. around a first time instant the signal changes from a first level to a second level and around a second instant the signal changes to a third level. This makes it possible to reduce a mechanical resonance vibration having a period of twice the time interval between the two instants.

Low vibration pulse drive device for an electric motor

An electrodeless low-pressure discharge lamp comprising a glass lamp vessel (1) which is sealed in a gas-tight manner and is filled with a metal vapor and a rare gas, this lamp vessel being provided with a tubular protuberance (2) which accommodates a rod-shaped core (3) of magnetic material surrounded by a wire winding (4) connected to a high-frequency supply unit, by means of which during operation of the lamp an electrical discharge is maintained in the lamp vessel, the inner side of the lamp vessel being provided with a transparent conductive layer (10), which is electrically connected by means of a lead-through member (12) to a conductor, such as a metal rod (11) provided in the core (3), located outside the lamp vessel, this lead-through member (12) being located at the end of the tubular protuberance, and being electrically connected to the internal conductive layer, for example by means of a wire spring (15).

Electrodeless low-pressure discharge lamp

An electrodeless low-pressure discharge lamp comprising a glass lamp vessel sealed in a gas-tight manner and filled with a metal vapor and a rare gas, and a winding on a ferrite core. During lamp operation an electrical discharge is maintained in the lamp vessel by the winding connected to a high-frequency supply. The winding is surrounded by a thin-walled cylindrical metal body or layer which is electrically insulated from the winding, is interrupted at at least one area and is connected during operation of the lamp to one of the power mains conductors.

An electrodeless low-pressure discharge lamp having a lamp vessel (1), a core (3) of magnetic material, a first winding (7) arranged to surround the core and connected to a high-frequency supply unit (4), one of the lead-in wires of this winding being electrically connected to a lead-in wire of a second winding (11) with a free end (12), while during operation of the lamp the potential drop between the ends of the second winding is substantially equal to the potential drop between the ends of the first winding and the potential drops in the two windings vary in opposite senses. Interference currents at the supply mains to which the lamp is connected are then strongly suppressed.

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Eindhoven, Netherlands

Andreas C Van Veghel