Mechanical Rectifier Research Articles

X-ray Therapy in Non-malignant Skin Lesions

THAT the X-ray is the most valuable single agency used in dermatological therapeutics, is an oft-stated axiom and one that becomes more evident with improved apparatus, technic, diagnostic ability, and knowledge of the biological action of roentgen rays. That workers of twenty or more years' experience have affection but no yearning for their earlier technic is not surprising. Any therapeutic agent to be the one of choice in a given condition must combine safety, accuracy, and efficiency. One often discards an effective therapeutic procedure because of technical difficulties or possible bad end-results. That roentgen therapy has survived the “experimental stage” is a tribute to our pioneers. But with improvement in apparatus, the development of direct and indirect methods of measurement using the Sabouraud Noire pastille, the Holzknecht, Hampson, Corbett and Kienböck units, MacKee's arithmetical computation, etc., we still lack a universal understandable description of technic—how often in presumably scientific communications do we read that the author gave so many minutes or milliamperes of X-ray. With numbers of such glaring examples easily recalled, one may perhaps be excused for a more or less complete description of the technic used. Author's Technic (After MacKee) Interrupterless transformers capable of supplying peak voltage up to 150 K.V., and with mechanical rectification, are used. Medium focus Coolidge tubes obtain primary current from step-down transformers controlled by a sensitive choke coil. Pre-reading voltmeters and milliamperemeters are mounted on the control board. Voltmeters are calibrated by sphere gaps mounted at tube, using fixed amperage and 100 K.V. for unfiltered and 130 for filtered applications, the filter used being 3 mm. of aluminum. The distance used in unfiltered treatment is 8 inches from the anode; with filters, 10 inches. Milliamperage of 2 or 4 in unfiltered and 5 in filtered applications is utilized. With these factors a faint but definite erythema is produced on the forearm by exposing successively 1 inch square areas to increasing amounts of ray. This amount is further checked (unfiltered) in cases of tinea capitis by the production of temporary depilation without erythema. Having thus standardized the apparatus, variations may be mathematically obtained in accordance with the following rules: 1. Quantity varies with the square of the voltage. 2. Quantity varies directly with the milliamperage. 3. Quantity varies directly with the time. 4. Quantity varies inversely with the square of the distance. Most skin diseases are treated with unfiltered rays because the pathology is superficially located and because unnecessary penetration and corresponding depth effects are unnecessary, and even, perhaps, injurious.

A High Voltage Mechanical Rectifier

A mechanical power rectifier for high voltage direct current production is described, and its design and operation discussed.

Electrical engineering features of the electrical precipitation process

In the beginning, the Cottrell Process of Electrical Precipitation was greatly handicapped by the fact that there did not exist standard electrical equipment which could be used to develop the necessary potentials under the severe conditions imposed by the mechanical rectifier, used for rectifying the high-potential alternating current. The transformers used were a constant source of trouble and annoyance. This condition delayed the rapid accumulation of accurate data pertaining to precipitation phenomena, since those engaged in the work were kept busy in merely maintaining a source of power. It was not long, however, before the electrical manufacturing companies were interested in the problems involved, and better transformers were produced. These transformers have now been developed to a degree which is very nearly the equal of the ordinary power transformers of the same voltage ratings. For several years there was a demand for higher and higher voltage ratings, owing to the belief that through the use of very high potentials and consequent large electrode spacing the size and cost of precipitators could be greatly reduced. Potentials as high as 250,000 volts were experimented with, but such high voltages proved to be impractical. Transformers were finally standardized at a voltage ratio of 220 or 440 to 100,000 volts, with taps in the low tension to give 50, 62.5, 75, 87.5 and 100 kilovolts. The capacities were 10, 15 and 25 kv-a. The 100,000-volt transformer of 15-kv-a. capacity has been used in the majority of installations.

Electrical Engineering Features of the Electrical Precipitation Process

In the beginning, the Cottrell Process of Electrical Precipitation was greatly handicapped by the fact that there did not exist standard electrical equipment which could be used to develop the necessary potentials under the severe conditions imposed by the mechanical rectifier, used for rectifying the high-potential alternating current. The transformers used were a constant source of trouble and annoyance. This condition delayed the rapid accumulation of accurate data pertaining to precipitattion phenomena, since those engaged in the work were kept busy in merely maintaining a source of power. It was not long, however, before the electrical manufacturing companies were interested in the problems involved, and better transformers were produced. These transformers have now been developed to a degree which is very nearly the equal of the ordinary power transformiers of the same voltage ratings. For several years there was a demand for higher and higher voltage ratings, owing to the belief that through the use of very high potentials and consequent large electrode spacing the size and cost of precipitators could be greatly reduced. Potentials as high as 250,000 volts were experimented with, but such high voltages proved to be impractical. Transformers as now standardized are in two voltage ranges, one with a maximum voltage of 75,000 volts having taps in the low tension to deliver 50, 60, 65 and 70 kilovolts, the other having a maxim nam voltage rating of 100,000 volts with taps in the low tension to deliver 50, 62?, 75 and 87? kilovolts.

A Portable Röntgen Ray Generating Unit

By W. D. COOLIDGE and C. N. MOORE. Introduction. When it became apparent that this country was to become involved in the European War, various Red Cross Units were formed and some of these instituted enquiries concerning X-ray apparatus suitable for war needs. It was through such enquiries that the authors became interested in the problem of a portable X-ray generating outfit. It seemed at the time to be generally felt b y Rontgenologists that nothing which was entirely satisfactory for this work had been evolved in this country. The problem as it first presented itself seemed rather indefinite, as but little was generally known concerning the degree of portability required, the current and voltage needed to operate the tube, the amount of service which would be required of the apparatus, the question as to whether power could usually be had from existing electric circuits, etc.,* Types of Apparatus Investigated. The various types of apparatus which the authors seriously considered for the purpose were :— (1) A gasoline-electric set furnishing low voltage direct current to a rotary convertor, with a step-up transformer and a mechanical rectifier attached to the shaft of the rotary. (2) A gasoline-electric set furnishing alternating current to a step-up transformer and with a mechanical rectifier driven from a small synchronous motor. (3) The same as 2, except for the substitution of a kenotron for the synchronous motor and mechanical rectifier. (4) A gasoline-electric set furnishing alternating current to a step-up transformer, with a self-rectifying X-ray tube operating directly from the latter. (5) A storage battery operating an induction coil through a mechanical interruptor or a mercury-turbine interrupter with suitable gas dielectric. (6) A storage battery operating a motor generator and so producing alternating current to be fed to a step-up transformer and thence to a self-rectifying X-ray tube.