US4376894A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Device for driving a rotary-anode X-ray tube
Assignee: US Philips Corp
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Filing: 1982-02-01
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Granted: 1983-03-15
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Expires: 2002-02-01
Abstract
Abstract The invention relates to a drive system for a rotary-anode X-ray tube which comprises an asynchronous motor. The current through the stator windings is generated by two pulse-width modulators to which sinusoidal signals which are phase-shifted 90° with respect to one another are supplied by a sine and a cosine memory. The amplitude thereof is controlled in dependence on the amplitude of the current through the relevant stator winding.
Inventors
- 👤 Gerd Vogler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 09:33
CPC Classifications
H; H02; H02P; H02P23/00; H02P23/08
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
171 words
In a device for driving a rotary-anode X-ray tube comprising an asynchronous motor having stator windings each supplied with an alternating current of predetermined frequency via a respective switching amplifier, the improvement comprising: (a) a pulse width modulator for controlling a respective switching amplifier, the pulse-width modulator producing an output signal having a high pulse frequency in comparison with the motor speed, (b) an alternating voltage generator for each stator winding, the various alternating voltage generators generating output phase-shifted sinusoidal alternating voltages, (c) a current measuring member for each stator winding for measuring the current through the stator windings, an output signal of said current measuring member being compared with a reference value signal in a comparison circuit, (d) means connecting the output of an alternating voltage generator to an input of the pulse-width modulator, at least the switching amplifier, the current measuring member and the comparison circuit forming a control loop for reducing the difference signal between the reference value signal and the output signal of the current measuring member.
Claim 2
Dependent Claim
171 words
In a device for driving a rotary-anode X-ray tube comprising an asynchronous motor having stator windings each supplied with an alternating current of predetermined frequency via a respective switching amplifier, the improvement comprising: (a) a pulse width modulator for controlling a respective switching amplifier, the pulse-width modulator producing an output signal having a high pulse frequency in comparison with the motor speed, (b) an alternating voltage generator for each stator winding, the various alternating voltage generators generating output phase-shifted sinusoidal alternating voltages, (c) a current measuring member for each stator winding for measuring the current through the stator windings, an output signal of said current measuring member being compared with a reference value signal in a comparison circuit, (d) means connecting the output of an alternating voltage generator to an input of the pulse-width modulator, at least the switching amplifier, the current measuring member and the comparison circuit forming a control loop for reducing the difference signal between the reference value signal and the output signal of the current measuring member.
Claim 3
Dependent Claim
47 words
A device as claimed in claim 1, wherein each alternating voltage generator comprises a digital circuit for generating a digital signal which corresponds to a sine function or a cosine function, and means connecting an output of the digital circuit to an input of a digital-to-analog converter.
Claim 4
Dependent Claim
29 words
A device as claimed in claim 2 wherein the digital-to-analog converters comprise multiplying digital-to-analog converters having an analog input which receives an output signal of an associated comparison circuit.
Claim 5
Dependent Claim
70 words
A device as claimed in claim 2 wherein the digital circuits comprise read-only memories having memory locations in which are stored the values of a cosine or a sine function, respectively, the values stored being addressed by means of a cyclical counter coupled to address inputs of the read-only memory, said counter being controlled by a clock generator, the frequency of the clock generator being controlled by a control device.
Claim 6
Dependent Claim
97 words
A device as claimed in claim 4 wherein the control device comprises a comparator circuit for comparing an actual value signal corresponding to the actual speed of the rotary anode with a predetermined reference value signal and for adding to or subtracting from the actual value signal a threshold voltage value which corresponds to the motor slip when the actual value signal exceeds or drops below the reference value signal, respectively, by a predetermined threshold voltage value, and for applying the signal thus formed to a control input of the clock generator as a frequency control variable.
References Cited (Backward Citations)
US4259580A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-03-14 | 1986-09-13 | 1987-03-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-03-14 | 1990-09-13 | 1991-03-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-03-14 | 1994-09-13 | 1995-03-15 | $7700.00 | Window Closed / Lapsed |