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US3015783A - High-frequency oven for high powers - Google Patents

High-frequency oven for high powers Download PDF

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Publication number
US3015783A
US3015783A US740717A US74071758A US3015783A US 3015783 A US3015783 A US 3015783A US 740717 A US740717 A US 740717A US 74071758 A US74071758 A US 74071758A US 3015783 A US3015783 A US 3015783A
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US
United States
Prior art keywords
circuit
voltage
discharge tube
anode
frequency
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US740717A
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English (en)
Inventor
Horst Hajo Lorens Van Der
Peter Hubertus Gerardu Vlodrop
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
US Philips Corp
North American Philips Co Inc
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US Philips Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by US Philips Corp filed Critical US Philips Corp
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Publication of US3015783A publication Critical patent/US3015783A/en
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B7/00—Generation of oscillations using active element having a negative resistance between two of its electrodes
    • H03B7/02—Generation of oscillations using active element having a negative resistance between two of its electrodes with frequency-determining element comprising lumped inductance and capacitance
    • H03B7/10—Generation of oscillations using active element having a negative resistance between two of its electrodes with frequency-determining element comprising lumped inductance and capacitance active element being gas-discharge or arc-discharge tube
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/04—Sources of current
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/06—Control, e.g. of temperature, of power

Definitions

  • the present-invention relates to high frequency. oven circuit arrangements. More particularly, the invention relates to high frequency oven circuit arrangements for high powers, for example several tens of kilowatts, having a gaseous discharge tube for exciting an oscillatory circuit, the gaseous discharge tube having a control electrode which, when oscillations of considerable amplitude are still present in the oscillatory circuit of the high-fre quency oven circuit arrangement, has supplied to it periodical ignition pulses derived from a separate relaxation generator having a grid-controlled discharge tube.
  • the gaseous discharge tube used in such high-frequency ovencircuit arrangement may. bev of difierent types, for example gaseous discharge tubes having a thermionic cathode. and a grid-like control'electrode, or gaseous dis charge tubes having a mercurypool cathode and a control electrode or ignition electrode arranged therein in an insulated manner.
  • difierent types for example gaseous discharge tubes having a thermionic cathode. and a grid-like control'electrode, or gaseous dis charge tubes having a mercurypool cathode and a control electrode or ignition electrode arranged therein in an insulated manner.
  • control-grid circuit of the discharge tube is connected in a relaxation.
  • the ignition pulses cause ignition of the gaseous discharge tube each time the anode voltage of the gaseous discharge tube constituted by the direct anode voltage and the superim posed alternating voltage of the circuit .has in practice a minimum value.
  • FIG. 1 shows a high-frequency oven according to the invention
  • FIGS. 2a-2c show several time diagrams toexplain the performance of the high-frequency oven of FIG. 1.
  • the high-frequency oven shown in FIG. 1 which is designed, for example, for a power of kw., has a discharge tube 1 filled with hydrogen gas, for exciting an oscillatory circuit 2 constituted by a circuit capacitor 3 and a circuit coil 4.
  • the circuit coil 4 is coupled to a coupling coil 5, which is connected to a work-coil 6 containing a load 7.
  • a charging capacitor 8 Connected in series with-the oscillatory circuit 2 is a charging capacitor 8, which is connected through a choking coil 9 to a direct-current source 10 constituted, for example, by a three phase rectifier, a coil 11 being included between the charging capacitor 8 and the anode of tube 1.
  • a direct-current source 10 constituted, for example, by a three phase rectifier, a coil 11 being included between the charging capacitor 8 and the anode of tube 1.
  • the gaseous discharge tube 1 has a control electrode which, when oscillations of considerable amplitude are still present in oscillatory circuit 2, has supplied to it periodical ignition pulses provided by a separate relaxation generator.
  • the relaxation generator comprises a thyratron 13 which normally is cut ofiby a negative grid-bias source 12.
  • the anode circuit cludes the series-combination of a resistor 16 and a coil 7 17.
  • the relaxation capacitor is charged across resistor 14 during each cycle at. a charging speed determined by the time constant of resistor 14 and capacitor 15.
  • the relaxation capfacitor 15 Upon every ignition of thyratron 13, the relaxation capfacitor 15 is discharged, resulting in a positive pulse across the cathode impedance 16, 17of said thyratron.
  • the thyratron 13 produced pulse is supplied through a blocking capacitor 18 to the control grid of a thyratron 1:9,is connected as a pulse producer.
  • the thyratron '19 which normally is cut-off by a negative grid-bias provided by grid-voltage source 12, includes a delay line 20 in its anode circuit, ,its cathode circuit including a resistor 21.
  • the delay line 20 discharges through thyratron l9'and across the. cathode resistor 21 thereis setup a positive rectangularpulse which is supplied as an ignition pulse through resistor- 22 to the control electrode o gaseous discharge tube 1.
  • the vcontrol gridof thyratron 13 has also suppliedto it a sinusoidal voltage provided by the oscillatory circuit 2 of the high-frequency oven circuit arrangement.
  • the sinusoidal voltage is derived from a coil 24 coupled to the oscillatory circuit 2.
  • an ignition pulse is produced, which occurs at amornent when the anode voltage of the gaseous discharge tube 1, which is constituted by the direct anode voltage and the superimposed alternating voltage of the circuit,has a minimum value.
  • FIG. 2a shows the voltage at the anode of gaseous discharge tube 1, which is constituted by the direct voltage across chargingcapacitor 8 as represented by the dotted curve 25and the superimposed voltage 26 of the circuit.
  • the gaseous discharge tube 1 is ignited by an ignition pulse, resulting in the circuit capacitor 3 being charged by the charging capacitor 8 via the series-coil 11 until tube 1 is extinguished at the moment when the anode voltage of gaseous discharge tube.
  • the energy in the oscillatory circuit 2 can now swing out freely, resulting ina damped oscillation 26, while charging capacitor 8 is charged by the direct-current source 10 via choke coil 9 in accordance with curve 25.
  • charging capacitor 8 and coil 11 which charging current Patented Jan. 2, 1962- is proportional to the instantaneous anode voltage and may be several hundreds or thousands of amperes.
  • the value of this charging current is dependent upon the amplitude of the sinusoidal oscillation in the oscillatory circuit 2 upon occurrence of an ignition pulse, which amplitude is determined by the load on the high-frequency'oven, said charging current increasing with increasing load on the high-frequency oven.
  • step according to the invention it is ensured that the circuit capacitor 3 isrecharged to its initial maximum value with minimum charge shift without any interfering building-up phenomena and it has been found that a considerable improvement in efficiency is thus obtained, for example an efliciency of more than70%.
  • a further advantage of the indicated step is that the elements of the high-frequency oven may be proportioned for a lower power.
  • FIG. 2b shows the grid voltage of the thyratron 13, which is connected as a relaxation generator, said grid voltage being constituted by a sawtooth voltage 27 with. the sinusoidal voltage 28 derived from oscillatory circuit 2 superimposed thereon.
  • the thyratron 13 is'ignited' and an ignition pulse occurs, which, as may be seen from the figure, coincides with a minimum value of the anode;
  • FIG. 20 shows the ignition pulses produced.
  • the recurrence' frequency of the ignition pulses is, for example, 250 c./sec. and the frequency of the oscillations occurring in oscillatory circuit 2 is 10 kc./ sec.
  • the useful output of the described high-frequency oven may be adjusted within very wide limits, for example, from about 0 kw. to about 7 kw., in a particularly simple manner by varying the recurrence frequency of the igni-1 tion pulses. This is effected by adjusting the adjustable voltage divider 23 included in the control-grid circuit of thyratron 13.
  • the ignition of the gaseous discharge tube 1 always takes place at a minimum anode voltage of gaseous discharge tube 1, thus resulting in a favourable output.
  • the ignition frequency may vary due to the amplitude of the sinusoidal voltage applied to the control grid varying with the load. For example, when the load onthe high-frequency oven is small, the amplitude of the sinusoidal voltage has a high value and the thyratron 13 can ignite at a preceding peak of thesinusoidal voltage. This results in an increased recurrence frequency of the ignition pulses,.which under certain conditions may be objectionable in connection with the useful output.
  • the sinusoidal voltage of oscillatory circuit 2 which is applied to the control grid of thyratron 13, is also applied via a resistor 30 to a rectifier stage 31, which provides a negative voltage in series with the voltage of the grid-bias source 12.
  • the blocking voltage of the thyratron thus varies with the mean amplitude of the oscillations occurring in oscillatory circuit 2, with the result that variations in the recurrence frequency of thee ignition pulses are counteracted or avoided.
  • a high frequency circuit arrangement compr sing for. deriving an auxiliary substantially sinusoidal voltage.
  • a gaseous discharge tube having an anode and a control electrode, means for supplying a direct voltage to said anode, a resonant circuit connected to said anode, a load circuit connected to said resonant circuit, means for periodically initiating the operation of said discharge tube thereby to periodically energize said resonant circuit, said last-mentioned means comprising an electrical discharge device having a control electrode and an output electrode, means for applying a signal having a substantially sawtooth waveform to said control electrode, means for deriving an auxiliary voltage from said resonant circuit and for superimposing the'same on said signal, and means for connecting said output electrode to the control electrode of said gaseousdischarge tube.
  • a high frequency circuit arrangement comprising ;a gaseous discharge tube having an anode andv a control electrode, means for supplying a direct voltage to said anode comprising an energy storing capacitor, a resonant circuitconnected to said anode and said capacitor in series circuit arrangement, a load circuit connected to said resonant circuit, means for periodically initiating the operation of said discharge tube thereby to periodically discharge said capacitor through said resonant circuit,v
  • said last-mentioned means comprising an electrical discharge device having a control electrode and an output electrode, means for applying a signal having a substantially sawtooth waveform to'said control electrode, means from said resonant circuit'and for superimposing the same on said signal, and means connecting said output electrodeto the control electrode of said gaseous discharge tube.
  • a high frequency circuit arrangement comprising a gaseous discharge tube having an anode and a control electrode,.input means for a direct voltage source, an
  • inductor interconnecting said input means and said anode, an energy storing-capacitor, a resonant circuit connected.
  • said last-mentioned means comprising a gaseous discharge tube having a control electrode, a capacitor and an impedance connected to form a relaxation oscillator generating a first signal having a substantially sawtooth waveform and a second signal having a pulse waveform, means for applying said first signal to said last-mentioned control electrode, means for deriving an auxiliary voltage from said resonant circuit and for superimposing the same on said first signal, and means responsive to said second signal for initiating the operation of said first-mentioned discharge tube.
  • a high frequency circuit arrangement comprising a gaseous discharge tube having an anode and a control electrode, means for supplying a direct voltage to said anode comprising an energy storing capacitor, a resonant circuit connected to said anode and said capacitor in series circuit arrangement, a load circuit connected to said resonant circuit, means for initiating the operation of said discharge tube thereby to periodically discharge said capacitor through said resonant circuit, said lastmentioned means comprising a gaseous discharge tube having a control electrode, a capacitor and an impedance connected to form a relaxation oscillator generating a first signal having a substantially sawtooth waveform and a second signal having a pulse waveform, means for applying said first signal to said last-mentioned control electrode, means for deriving an auxiliary voltage from said resonant circuit and for superimposing the same on said first signal, means for deriving from said auxiliary voltage a biasing voltage having variations as determined by the variations of said auxiliary voltage, means for applying said biasing voltage to said last-
  • a high frequency c1rcu1t arrangement as claimed in claim 4 further comprising means for adjusting the 2,492,161 F 1949 intensity of said first signal applied to the said second- 5 2,591,660 Lmdley et 1952 mentioned control electrode. 2,852,676 Joy Sept 1958

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Generation Of Surge Voltage And Current (AREA)
  • Control Of Electrical Variables (AREA)
US740717A 1957-07-13 1958-06-09 High-frequency oven for high powers Expired - Lifetime US3015783A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL359224X 1957-07-13

Publications (1)

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US3015783A true US3015783A (en) 1962-01-02

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US740717A Expired - Lifetime US3015783A (en) 1957-07-13 1958-06-09 High-frequency oven for high powers
US740923A Expired - Lifetime US3024427A (en) 1957-07-13 1958-06-09 Oscillator power control

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US740923A Expired - Lifetime US3024427A (en) 1957-07-13 1958-06-09 Oscillator power control

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US (2) US3015783A (el)
BE (2) BE569358A (el)
CH (2) CH359224A (el)
FR (2) FR1207784A (el)
GB (2) GB894917A (el)
NL (1) NL218928A (el)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3673437A (en) * 1970-06-29 1972-06-27 Minnesota Mining & Mfg Damped sinusoidal current pulse generator and method
US3760279A (en) * 1971-09-16 1973-09-18 United States Steel Corp Beam current limiting circuit

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3566148A (en) * 1968-02-14 1971-02-23 Westinghouse Electric Corp Selective phase angle pulse generating circuit
US3770928A (en) * 1971-12-27 1973-11-06 Gen Electric Reliable solid state induction cooking appliance with control logic

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2492161A (en) * 1943-06-01 1949-12-27 Int Standard Electric Corp Means for generating time modulated electrical pulses
US2591660A (en) * 1947-11-08 1952-04-01 Radio Television Inst Inc Stabilized electrical synchronizing system
US2852676A (en) * 1955-02-15 1958-09-16 Ivan L Joy Voltage train generating device

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2733340A (en) * 1956-01-31 Wave amplitude control high-q load
US2475063A (en) * 1944-02-24 1949-07-05 Rca Corp Regulated high-voltage apparatus
US2508321A (en) * 1945-09-05 1950-05-16 Raymond M Wilmotte Method and means of controlling electronic heating
US2896169A (en) * 1955-10-24 1959-07-21 Gen Electric Automatic frequency control system with a two-speed frequency sweep

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2492161A (en) * 1943-06-01 1949-12-27 Int Standard Electric Corp Means for generating time modulated electrical pulses
US2591660A (en) * 1947-11-08 1952-04-01 Radio Television Inst Inc Stabilized electrical synchronizing system
US2852676A (en) * 1955-02-15 1958-09-16 Ivan L Joy Voltage train generating device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3673437A (en) * 1970-06-29 1972-06-27 Minnesota Mining & Mfg Damped sinusoidal current pulse generator and method
US3760279A (en) * 1971-09-16 1973-09-18 United States Steel Corp Beam current limiting circuit

Also Published As

Publication number Publication date
BE569359A (el)
FR1207785A (fr) 1960-02-18
CH359225A (de) 1961-12-31
FR1207784A (fr) 1960-02-18
GB843322A (en) 1960-08-04
NL218928A (el)
BE569358A (el)
CH359224A (de) 1961-12-31
US3024427A (en) 1962-03-06
GB894917A (en) 1962-04-26

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