Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Patent
1991-08-12
1992-10-27
Stephan, Steven L.
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
323903, 55139, B03C 302
Patent
active
051595443
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION FIELD OF THE INVENTION
This invention relates to electrical circuits for generating high magnitude electrostatic potentials, and particularly to a system for driving a high voltage transformer. The system utilizes a phase-lock technique to drive the high voltage transformer at or near its resonant frequency. The invention is disclosed in the context of high magnitude electrostatic potential generating systems for use in electrostatically-aided coating material application systems, such as liquid and powder coating systems.
DESCRIPTION OF THE RELATED ART
Industrial electrostatic coating systems typically use high voltage direct current power supplies to produce high magnitude potentials of up to 150 kilovolts (KV) DC across a pair of output terminals. One of the terminals is generally held at or near ground potential while the other terminal is held at a high magnitude (typically negative) potential. The high magnitude potential terminal is coupled to a device that charges particles of the coating material as they are dispensed.
Articles to be coated are maintained at a low magnitude potential, typically at or near ground. The articles can be moved past the coating dispensing device, for example, on a conveyor. The atomized and charged coating material moves through the electric field between the dispensing device and the article. The charged coating material strikes the article and sticks to it.
The possibility of spark discharge between the charging device and the articles and other nearby grounded surfaces creates a considerable hazard in industrial electrostatic coating systems. Certain materials used in coating processes are volatile and flammable. The desirability of a system which prevents such spark discharge is apparent.
Spark discharges may occur when the potential across the device-to-article space exceeds the dielectric strength of the space, such as when the device and article get too close to each other or when the magnitude of the potential on the device is permitted to get too high. Typical electrostatic coating systems use relatively large transformers operating at frequencies well below the knee of the frequency response curve of the transformer. In known electrostatic coating systems, the transformer is selected so that the desired output voltage (around 15 KV peak-to-peak) is obtained in the flat, linear range of the frequency response curve. Changes in the operating conditions of the system, such as when the operating frequency of the system varies, do not affect the transformer output voltage unless the operating frequency approaches the transformer resonant frequency. As the operating frequency approaches the transformer's resonant frequency, the voltage across the transformer's output terminals can increase fairly rapidly above the nominal voltage level, increasing the likelihood of a spark discharge.
Just prior to spark discharge, an increase in current across the high-magnitude potential terminals is ordinarily noted. This current increase has been the focus of much of the spark-discharge prevention equipment in use today . See, for example, U.S. Pat. Nos.: 3,851,618; 3,875,892; 3,894,272; 4,075,677; 4,187,527; and 4,402,030. It has also been noted, and use has been made of the fact in the prior art, that if the Stored energy in the charging/dispensing device and associated circuit components can be rapidly dissipated by this increase in current that presages a spark discharge, such a discharge can ordinarily be averted. See, for example, U.S. Pat. No. 4,745,520. Other prior art which may be of interest includes U.S. Pat. Nos.: 3,599,038; 3,608,823; 3,731,145; 4,165,022; and 4,331,298.
Two common methods are used for powering a transformer to drive the DC multiplier for generating high DC potentials necessary to operate the charging device. One method utilizes a self-sustaining power oscillator designed to operate at the resonant frequency of the transformer. The self-sustaining oscillator is inefficient because it operates in class A. In addition, u
REFERENCES:
patent: 2302185 (1942-11-01), Campbell, Jr.
patent: 2302289 (1942-11-01), Bramston-Cook
patent: 2509277 (1950-05-01), Ransburg et al.
patent: 2650329 (1953-08-01), Orndoff
patent: 2881092 (1959-04-01), Sedlacsik, Jr.
patent: 3048498 (1962-08-01), Juvinall et al.
patent: 3273015 (1966-09-01), Fischer
patent: 3367578 (1968-02-01), Juvinall et al.
patent: 3567996 (1971-03-01), Gordon et al.
patent: 3599038 (1971-08-01), Skidmore
patent: 3608823 (1971-09-01), Buschor
patent: 3641971 (1972-02-01), Walberg
patent: 3731145 (1973-05-01), Senay
patent: 3851618 (1974-12-01), Bentley
patent: 3872370 (1975-03-01), Regnault
patent: 3875892 (1975-04-01), Gregg et al.
patent: 3893006 (1975-07-01), Algeri et al.
patent: 3894272 (1975-07-01), Bentley
patent: 3895262 (1975-07-01), Ribnitz
patent: 4000443 (1976-12-01), Lever
patent: 4075677 (1978-02-01), Bentley
patent: 4103356 (1978-07-01), Finlay
patent: 4120015 (1978-10-01), Haller
patent: 4148932 (1979-04-01), Tada et al.
patent: 4165022 (1979-08-01), Bentley et al.
patent: 4187527 (1980-02-01), Bentley
patent: 4208706 (1980-06-01), Suzuki et al.
patent: 4210858 (1980-07-01), Ford et al.
patent: 4213167 (1980-07-01), Cumming et al.
patent: 4251735 (1981-02-01), Coleman
patent: 4257089 (1981-03-01), Ravis
patent: 4331298 (1982-05-01), Bentley et al.
patent: 4371917 (1983-02-01), Bator
patent: 4402030 (1983-08-01), Moser et al.
patent: 4463415 (1984-07-01), Vollrath
patent: 4480297 (1984-10-01), Chetty et al.
patent: 4481557 (1984-11-01), Woodruff
patent: 4485427 (1984-11-01), Woodruff et al.
patent: 4523267 (1985-06-01), Mehl
patent: 4535399 (1985-08-01), Szepesi
patent: 4560950 (1985-12-01), Cabot
patent: 4587475 (1986-05-01), Finney, Jr. et al.
patent: 4616300 (1986-10-01), Santelmann, Jr.
patent: 4652318 (1987-03-01), Masuda et al.
patent: 4672521 (1987-06-01), Riesco
patent: 4677534 (1987-06-01), Okochi
patent: 4700285 (1987-10-01), Szepesi
patent: 4710849 (1987-12-01), Norris
patent: 4730243 (1988-03-01), Glennon
patent: 4745520 (1988-05-01), Hughey
patent: 4783728 (1988-11-01), Hoffman
patent: 4893227 (1990-01-01), Gallios et al.
patent: 5008800 (1991-04-01), Klinkowstein
Data sheet for National Semiconductor's Type CD 4046 CMOS Integrated Circuit, May 1965.
Atherton Robert R.
Hughey Daniel C.
Ransburg Corporation
Stephan Steven L.
Sterrett Jeffrey
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