Abstract: Starting and operating method and apparatus for discharge lamps comprises a current-limiting and rectifying means which provides at its output a low-ripple current-limited direct current. To effect lamp starting, a series-connected inductor and capacitor form a high "Q" resonant circuit with the capacitor connected across the lamp to be operated. This starting circuit connects through a blocking capacitor and charging resistor across the low-ripple source of DC. A pair of transistors which comprise an oscillator are connected emitter-to-collector across the source of DC, with the common-connected emitter and collector connected to the blocking capacitor. A drive air-core transformer has separate feedback windings in the starting and operating circuits and drive windings are associated with the transistors. A trigger diode is used to initially pulse one of the transistors which initially oscillate to generate square waves having a frequency corresponding to the resonant frequency of the starting circuit.

Abstract: Lead-type ballast apparatus operable to program and control the operating performance of a high-intensity-discharge sodium lamp. The basic lead-type ballast comprises a current-limiting high-reactance transformer having a capacitor connected between the transformer output terminals and the lamp to be operated. A pulse-generating means is normally associated with the transformer secondary and is operable to generate high-voltage pulses when the apparatus is energized which are applied through the capacitor to initiate a discharge within the lamp. There is also provided an additional inductor which is connected in circuit in one of (1) a parallel connection across the capacitor and (2) a connection across the transformer secondary. An "open or closed" switch connects in circuit with the additional inductor. A sensing and programming means operates to sense at least one lamp operating parameter to control the proportion of time the switch is open and closed, in order to vary the current input to the lamp.

Abstract: Add-on device for lead-type ballast comprises additional inductor and series-connected controlled AC switching means which are connected in parallel circuit with the capacitor portion of the lead-type ballast such as is used to operate an HID sodium lamp. The add-on device has a sensing and control circuit which operates to sense a lamp operating parameter in order to control the actuation of the AC switching means which in turn controls in predetermined fashion the operation of the ballasted lamp. The inductor and AC switch and sensing and control means of the add-on device are all packaged within a can-shaped member which has dimensions similar to those of the conventional capacitor can for the lead-type ballast. All the elements of the add-on device are potted within the capacitor can with terminal means extending from an end portion thereof for ready connection along with an exposed potentiometer portion to enable the control to be adjusted.

Abstract: Composite structure for use as an HID device ballast component and which performs the dual functions of voltage transformation and provision of ballasting reactance which can be cntrollably shifted in value. A multi-leg magnetic structure has a primary winding carried on a first leg thereof and an output winding carried on a second leg thereof. A control winding is carried on a third leg and a gap of predetermined dimensions is provided in the magnetic path which includes the third leg. The magnetic core member and the windings carried thereon display leakage flux paths of predetermined total permeance. A bilateral switch connects to the control winding and is operable to be closed once each half cycle of normal lamp operation. With the control winding closed, the counter mmf generated in the third leg decreases the inductive reactance of the structure by a predetermined amount, with the inductive reactance of the structure essentially established by the permeance of the leakage paths.

Abstract: An injection transformer has a primary winding series connected with a pair of inverse parallel-connected thyristors between a pair of input terminals. A control circuit is connected across a pair of output terminals for firing the thyristors. The injection transformer has a secondary winding connected between one of the input terminals and one of the output terminals for producing an injection voltage. A filter has components presenting a high impedance to the harmonic frequencies of the injection voltage and a low impedance to the fundamental frequency of the injection voltage, and has components presenting a high impedance to the fundamental frequency of the injection voltage and a low impedance to the harmonic frequencies of the injection voltage.

Abstract: The primary and secondary core sections of a split core transformer forming an inductive coupler are secured within separate sealed containments in intimate contact with a thin non-magnetic portion of the respective containments which permits inductive coupling and decoupling of the primary and secondary core sections in corrosive fluid environments such as water. The sealed containments isolate the core sections from contact with the corrosive environment thus permitting the use of efficient laminated iron in otherwise corrosive environments.