Power supply for refrigeration units

{
  "publication_number": "US3875483A",
  "country": "US",
  "kind": "A",
  "title": "Power supply for refrigeration units",
  "abstract": "An electronic power supply which derives power from a DC battery to operate the AC induction motor of a refrigeration compressor unit. The amplitude and frequency of the AC voltage developed by the power supply from the DC battery are functions of the battery voltage. When the battery voltage increases, the amplitude and frequency of the AC voltage for driving the motor increase and vice versa to thereby efficiently operate the motor in spite of fluctuation in the level of battery voltage.",
  "claims": [
    "1. In a refrigeration system and power supply therefor of the type adapted for use in a mobile vehicle such as a camper, a trailer or the like, the combination comprising a refrigeration compressor driven by an AC induction motor, an evaporator coil and a condenser coil operatively connected to said compressor, a DC battery having a nominal battery output voltage that is subject to variation within a predetermined range according to the charge and the load on said battery, and inverter circuit means operably coupling said battery to said motor for energizing said motor with an AC voltage whose amplitude and frequency vary according to preselected functions of battery voltage, said inverter circuit means comprising amplitude control means and frequency control means, said amplitude control means comprising first and second switch means adapted to be alternately rendered conductive in response to first and second switching signals respectively, first output means operatively coupled to said first switch means and said battery so as to be energized when said first switch means is conducting to provide one polarity half cycle of said AC voltage, second output means operatively coupled to said second switch means and said battery so as to be energized when said second switch means is conducting to provide the opposite polarity half cycle of said AC voltage, said amplitude control means being responsive to battery voltage variations within said range for controlling said AC voltage amplitude such that when battery voltage increases within said range said AC voltage amplitude increases according to a first preselected function and when said battery voltage decreases within said range said AC voltage amplitude decreases according to said first preselected function, and wherein said frequency control means comprises signal generating means including oscillator means for generating said first and second switching signals, said signal generating means being coupled to said first and second switch means and also being connected to and powered by said battery and responsive to said battery voltage variations within said range to vary the frequency of said switching signals and thereby vary said AC voltage frequency developed by said first and second output means, said generating means being responsive to battery voltage variations within said range such that when battery voltage increases within said range said AC voltage frequency increases according to a second preselected function and when said battery voltage decreases within said range said AC voltage frequency decreases according to said second preselected function wherein said motor is efficiently operated at different torque loads at said compressor even though said battery voltage varies within said range.",
    "2. The combination set forth in claim 1 wherein said first preselected function and said second preselected function are substantially linear functions and wherein said first and second functions are preselected relative to each other so that half cycles of said AC voltage have substantially equal volt second products even though said battery voltage varies within said range.",
    "3. The combination set forth in claim 1 wherein said motor is a sole electrical load for said inverter circuit means.",
    "4. The combination set forth in claim 1 wherein said first output means comprises a first primary winding of an output transformer, said first switch means is connected to one terminal of said first primary winding so as to conduct current therethrough in a first direction, the other terminal of said first primary winding is connected to said battery, said second output means comprises a second primary winding on said transformer, said second switch means is connected to one terminal of said second primary winding so as to conduct current therethrough in a first direction, and wherein said combination further comprises a diode reversely connected in parallel with said first switch means and poled in a direction to conduct current through said first primary winding in an opposite current direction, said oppositely directed current in said first primary winding being caused by flux developed by said second primary winding in response to current flow therethrough in said first current direction when said second switch means is conducting.",
    "5. The combination set forth in claim 4 wherein said diode is a Zener diode.",
    "6. A power supply circuit for use with a refrigeration system having a compressor unit driven by an AC induction motor wherein said circuit is to be energized by a DC battery to supply said motor with an AC voltage whose amplitude and frequency are varied as controlled functions of variations in battery voltage, said amplitude and said frequency increasing with increasing battery voltage and vice versa, said power supply circuit comprising an inverting transformer having a secondary winding adapted to be connected to said motor and further having first and second primary windings, first and second switching transistors associated with said first and second primary windings respectively with each of said transistors having a first terminal of its emitter-collector circuit connected to a first terminal of its associated primary winding and a second terminal of its emitter-collector circuit adapted to be connected to one terminal of said battery, means adapted to connect the second terminals of each primary winding to the other terminal of said battery, said first primary winding being arranged such that current flow therethrough when its associated switching transistor is conducting causes a positive flux to be developed in said secondary winding and said second primary winding being arranged such that current flow therethrough when its associated switching transistor is conducting causes a negative flux to be developed in said secondary winding, first and second additional transistors associated with said first and second switching transistors respectively and being operatively coupled in the base circuit of its associated switching transistor to control conduction thereof in response to periodic switching signals, oscillator means adapted to be connected to said battery and operable to generate said switching signals at an oscillation frequency that varies as a controlled function of battery voltage, coupling circuit means connecting said switching signals to the base-emitter circuits of said first and second additional transistors, and wherein said oscillator means, said coupling circuit means, said additional transistors and said switching transistors are arranged such that said switching transistors are rendered alternately conductive via their associated additional transistor in response to said switching signals to thereby alternately energize said primary windings, and said inverting transformer comprises first and second additional windings associated with said first and second primary windings respectively and wound such that opposite polarity voltage is simultaneously induced across each additional winding between corresponding terminals thereof by changing flux in said inverting transformer, each of said additional windings being electrically connected to its associated switching transistor such that when its associated switching transistor is initially rendered conducting to thereby initially energize its associated primary winding the voltage induced in the associated additional winding by the initial energization of the associated primary winding tends to increase the conduction of the associated switching transistor.",
    "7. The combinaTion set forth in claim 6 further comprising first rectifier means reversely connected in parallel with said first switching transistor and poled to conduct current through said first primary winding in a direction opposite to current through said first winding and said first switching transistor, and second rectifier means reversely connected in parallel with said switching transistor and poled to conduct current through said second primary winding in a direction opposite to current through said second winding and said second switching transistor.",
    "8. A power supply circuit for use with a refrigeration system having a compressor unit driven by an AC induction motor wherein said circuit is to be energized by a DC battery to supply said motor with an AC voltage whose amplitude and frequency are varied as controlled functions of variations in battery voltage, said amplitude and said frequency increasing with increasing battery voltage and vice versa, said power supply circuit comprising an inverting transformer having a secondary winding adapted to be connected to said motor and further having first and second primary windings, first and second switching transistors associated with said first and second primary windings respectively with each of said transistors having a first terminal of its emitter-collector circuit connected to a first terminal of its associated primary winding and a second terminal of its emitter-collector circuit adapted to be connected to one terminal of said battery, means adapted to connect the second terminals of each primary winding to the other terminal of said battery, said first primary winding being arranged such that current flow therethrough when its associated switching transistor is conducting causes a positive flux to be developed in said secondary winding and said second primary winding being arranged such that current flow therethrough when its associated switching transistor is conducting causes a negative flux to be developed in said secondary winding, first and second additional transistors associated with said first and second switching transistors respectively and being operatively coupled in the base circuit of its associated switching transistor to control conduction thereof in response to periodic switching signals, oscillator means adapted to be connected to said battery and operable to generate said switching signals at an oscillation frequency that varies as a controlled function of battery voltage, coupling circuit means connecting said switching signals to the base-emitter circuits of said first and second additional transistors, and wherein said oscillator means, said coupling circuit means, said additional transistors and said switching transistors are arranged such that said switching transistors are rendered alternately conductive via their associated additional transistor in response to said switching signals to thereby alternately energize said primary windings, and said oscillator means comprises bistable multivibrator means and pulse generating means adapted to be connected to the battery, said means connecting said oscillator means to said first and second electronic switches comprises means connecting said multivibrator means to said first and second switches, said oscillator means includes means connecting said pulse generating means to said multivibrator means and adapted to switch said multivibrator means between states to thereby alternately operate said first and second switches, said pulse generating means comprises means operable in accordance with the level of battery voltage for developing pulses at a frequency related to battery voltage and means for applying said pulses to said multivibrator means to cause said multivibrator means to change state in response to each pulse developed by said pulse generating means whereby said first and second switches are operated at a frequency related to battery voltage and are each operated for substantially equal durations for a given level of battery voltage. Pg,47",
    "9. In a refrigeration system, the combination comprising a refrigeration compressor driven by an AC induction motor, an evaporator coil and a condenser coil operatively connected to said compressor, a DC battery whose output voltage is subject to variation within a predetermined range according to the charge and the load on said battery, and inverter circuit means operably coupling said battery to said motor for energizing said motor with an AC voltage whose amplitude and frequency are preselected functions of battery voltage, said inverter circuit means comprising first and second switch means adapted to be alternately rendered conductive in response to first and second switching signals respectively, first output means operatively coupled to said first switch means and said battery so as to be energized when said first switch means is conducting to provide one polarity half cycle of said AC voltage, second output means operatively coupled to said first switch means and said battery so as to be energized when said second switch means is conducting to provide the opposite polarity half cycle of said AC voltage, said first and said second switch means being arranged and constructed so that when battery voltage increases within said range said AC voltage amplitude increases according to a first preselected function and when said battery voltage decreases within said range said AC voltage amplitude decreases according to said first preselected function, and signal generating means, including oscillator means and being coupled to said first and second switch means, for generating said first and second switching signals, said signal generating means also being connected to said battery and being arranged and constructed so that when battery voltage increases within said range said AC voltage frequency increases according to a second preselected function and when said battery voltage decreases within said range said AC voltage frequency decreases according to said second preselected function, and wherein said signal generating means includes reference means for developing a substantially constant reference voltage and means responsive to a voltage differential between said battery voltage and said reference voltage to vary the frequency of said oscillator and thereby vary the frequency of said switching signals whereby said motor is efficiently operated at different torque loads at said compressor even though said battery voltage varies within said range.",
    "10. The combination set forth in claim 9 wherein said first output means includes a first primary winding, said second output means includes a second primary winding, said first and said second primary windings being magnetically coupled to a secondary winding so as to develop said AC voltage therein, said first switch means including first and second electronic switching means, said second switch means comprising third and fourth electronic switching means, each of said first, second, third and fourth switching means having a pair of main electrodes and a control electrode for controlling conduction through its main electrodes, said second switching means being operatively connected to said control electrode of said first switching means so as to control conduction thereof in response to said first switching signal at said control electrode of said second switching means, said fourth switching means being operatively connected to said control electrode of said third switching means so as to control conduction thereof in response to said second switching signal and wherein said first primary winding is connected in series with said main electrodes of said first switching means across said battery, and said second primary winding is connected in series with said main electrodes of said third switching means across said battery.",
    "11. The combination set forth in claim 10 wherein said first primary winding has one terminal thereof connected to said battery and the other terminal thereof connected to one of said main electrodes of said first switching device, a first feedback winding magnetically coupled to said first primary winding and electrically coupled between said control electrode of said first switching means and one of said main electrodes of said second switching means, a diode electrically connected between said other terminal of said first primary winding and said one main electrode of said second switching means, and a resistor electrically connected between said other terminal of said first primary winding and said control electrode of said first switching means.",
    "12. In the combination of a refrigeration compressor unit driven by an AC induction motor, a DC battery and inverter circuit means operatively coupling said motor to said battery, the improvement wherein said inverter circuit means is operable in response to a DC battery voltage to develop an AC voltage for said motor wherein the amplitude and the frequency of said AC voltage are functions of said battery voltage, said frequency and said amplitude increasing with increasing battery voltage and vice versa, said inverter circuit means comprising transformer means having primary winding means, secondary winding means and magnetic circuit means linking said primary winding means and said secondary winding means, switching means electrically connected between said battery and said primary winding means and operable in response to periodic switching signals to switch between first and second states for effecting first and second connections respectively of said battery to said primary winding means so that when said switching means is in its first state the flux in said magnetic circuit means changes in one direction and when said switching means is in its second state the flux changes in the other direction to thereby develop said AC voltage in said secondary winding means with said AC voltage having an amplitude which varies as a function of battery voltage, means electrically connecting said secondary winding means to said motor for supplying said AC voltage thereto, oscillator means operatively coupled to said battery for developing said periodic switching signals at an oscillation frequency which varies as a function of battery voltage, and coupling circuit means operatively connecting said switching signals from said oscillator means to said switching means to switch said switching means at a frequency equal to said oscillation frequency, said oscillator means comprising balancing means for balancing the switching operation at said switching means between said first and second states so that said switching means operates for substantially equal time intervals in each of its two states whereby opposite polarity half cycles of said AC voltage may be balanced.",
    "13. The combination set forth in claim 12 wherein said balancing means comprises pulse generating means for timing said oscillation frequency at each half cycle thereof so as to effect said operation of said switching means for substantially equal time intervals in each of its two states, said pulse generating means being connected to said battery and operable in response to variations in battery voltage to vary the repetition rate of said pulses and thereby vary said oscillation frequency as a function of battery voltage.",
    "14. The combination set forth in claim 13 wherein said pulse generating means further comprises reference means for developing a substantially constant reference voltage and means for varying said repetition rate of said pulse generating means in response to voltage differences between said battery voltage and said reference voltage to thereby vary said oscillation frequency as a function of battery voltage.",
    "15. The combination set forth in claim 13 wherein said pulse generation means comprises a free-running oscillator whose frequency is twice said oscillation frequency of said oscillator means.",
    "16. The combination set forth in claim 12 wherein said oscillator means further comPrises reference means for developing a substantially constant reference voltage, and means responsive to voltage differences between said battery voltage and said reference voltage to vary said oscillation frequency as a function of battery voltage.",
    "17. The combinataion set forth in claim 12 wherein said oscillator means comprises free-running multivibrator means having first and second alternately conducting switch means each of which has a pair of main electrodes for conducting current therethrough and wherein said balancing means comprises variable impedance means connected in circuit with like electrodes of each of said switch means and said battery such that said impedance means may be varied to thereby vary relative conduction times of said first and second switch means and balance said switching operation.",
    "18. In the combination of a refrigeration compressor unit driven by an AC induction motor, a DC battery and inverter circuit means operatively coupling said motor to said battery, the improvement wherein said inverter circuit means is operable in response to a DC battery voltage to develop an AC voltage for said motor wherein the amplitude and the frequency of said AC voltage are functions of said battery voltage, said frequency and said amplitude increasing with increasing battery voltage and vice versa, said inverter circuit means comprising transformer means having primary winding means, secondary winding means and magnetic circuit means linking said primary winding means and said secondary winding means, switching means electrically connected between said battery and said primary winding means and operable in response to periodic switching signals to switch between first and second states for effecting first and second connections respectively of said battery to said primary winding means so that when said switching means is in its first state the flux in said magnetic circuit means changes in one direction and when said switching means is in its second state the flux changes in the other direction to thereby develop said AC voltage in said secondary winding means with said AC voltage having an amplitude which varies as a function of battery voltage, means electrically connecting said secondary winding means to said motor for supplying said AC voltage thereto, said inverter circuit means further comprising oscillator means operatively coupled to said battery for developing said periodic switching signals at an oscillation frequency which varies as a function of battery voltage, and coupling circuit means operatively connecting said switching signals from said oscillator means to said switching means to switch said switching means at a frequency equal to said oscillation frequency, and wherein said oscillator means comprises reference voltage means for supplying a substantially constant reference voltage, said oscillator means being responsive to the voltage differential between said battery and said reference voltage means for repetitively switching said switching means between said first and second states at an oscillation frequency related to the differential between battery voltage and the voltage of said reference voltage means.",
    "19. The combination set forth in claim 18 wherein said oscillator means further comprises pulse generating means for timing said oscillation frequency at each half cycle thereof so as to effect said operation of said switching means for substantially equal time intervals in each of its two states, said pulse generating means being connected to said battery and responsive to said reference voltage means to vary said repetition rate.",
    "20. In the combination of a refrigeration compressor unit driven by an AC induction motor, a DC battery and inverter circuit means operatively coupling said motor to said battery, the improvement wherein said inverter circuit means is operable in response to a DC battery voltage to develop an AC voltage for said motor wherein the amplitude and frequency of said AC voltage are functions of said battery voltage, said frequency and said amplitude increasing with increasing battery voltage and vice versa, said inverter circuit means comprising transformer means having first and second primary winding means and secondary winding means wound on magnetic circuit means, first and second electronic switch means each of which has a pair of main electrodes and a control electrode for controlling conduction through said main electrodes, said first switch means having its main electrodes connected between said battery and said first primary winding means, said second switch means having its main electrodes connected between said battery and said second primary winding means, third and fourth electronic switch means associated with said first and second switch means respectively, each of said third and fourth switch means having a pair of main electrodes and a control electrode for controlling conduction through its main electrodes, said third switch means being operatively coupled to said control electrode of its associated first switch means to render said first switch means conductive in response to a first periodic switching signal, said fourth switch means having its main electrodes operatively connected in circuit with said control electrode of its associated second switch means to render said second switch means conductive in response to a second periodic switching signal, said first and second primary winding means being arranged on said magnetic circuit means so that a flux of one polarity is developed therein when said first switch means is rendered conductive in response to said first switching signal and a flux of an opposite polarity is developed when said second switch means is rendered conductive in response to said second switching signal, and wherein said combination further comprises oscillator means for developing said first and second periodic switching signals at an oscillation frequency which varies as a function of battery voltage, coupling circuit means operatively connecting said switching signal from said oscillator means to said third and fourth switch means so as to render said first and second switch means alternately conductive, and first and second additional winding means on said magnetic circuit means, said first additional winding means being connected in circuit with said third switch means and said control electrode of said first switch means so as to assist said first switch means being rendered conductive by said third switch means and said second additional winding means being connected in circuit with said fourth switch means and said control electrode of said second switch means so as to assist said second switch means being rendered conductive by said fourth switch means.",
    "21. The combination set forth in claim 20 wherein said first, second, third and fourth switch means are respective first, second, third and fourth transistors, said battery has a pair of output terminals, said first primary winding is connected in series with the emitter-collector circuit of said first transistor across said output terminals said second primary winding means is connected in series with the emitter-collector circuit of said second transistor across said battery terminals, said first additional winding means has one terminal connected to the base of said first transistor and the other terminal thereof connected to the emitter-collector circuit of said third transistor, said second additional winding means has one terminal connected to the base of said second transistor and the other terminal therof connected to the emitter-collector circuit of said fourth transistor.",
    "22. The combination set forth in claim 21 wherein the emitter of said first transistor is connected to one terminal of said first primary winding, a rectifier is connected between said one terminal of said first primary winding and said other terminal of said first additional winding, and a resistor is connected between said one terminal of said first Primary winding and said base of said first switching transistor.",
    "23. The combination set forth in claim 20 wherein said oscillator means, said coupling means and said first, second, third and fourth transistors are arranged and constructed such that said first switch means is rendered conductive via said third switch means in response to said first switching signal when said second switch means is rendered nonconductive via said third switch means in response to said second switching signal and said first switch means is rendered nonconductive via said third switch means in response to said first switching signal when said second switch means is rendered conductive via said fourth switch means in response to said second switching signal.",
    "24. The combination of claim 5 wherein the terminals of one pair of corresponding terminals of said additional windings are respectively connected to the base terminals of said first and second switching transistors respectively and the terminals of the other pair of corresponding terminals of said additional windings are respectively connected to said first and second additional transistors respectively and further including first and second diodes associated with said first and second additional windings respectively, each of said diodes having one terminal connected to the junction of its associated additional winding and its associated additional transistor, and each of said diodes having its other terminal connected to the emitter terminal of its associated switching transistor whereby when the voltage induced in each additional winding by its associated primary winding drops to permit forward conduction of the associated diode, the associated diode shunts current from the base circuit of the associated switching transistor to increase the collector-emitter voltage thereof, and hence reduce the voltage across the associated primary winding, and the reduced voltage across the associated primary winding causes voltage to be developed in the associated additional winding which tends to further inhibit base current in the associated switching transistor.",
    "25. The combination of claim 8 wherein said pulse generating means includes reference voltage means for developing a substantially constant reference voltage during operation of said pulse generating means, said pulse generating means being operable to develop pulses at a frequency which is a function of the voltage difference between battery voltage and the voltage of said reference voltage means.",
    "26. The combination of claim 25 wherein said reference voltage means comprises a Zener diode."
  ],
  "cpc": [
    "H02P 27/06",
    "F25B 2600/021",
    "F25B 49/025",
    "H02M 7/5381",
    "H02P 27/047",
    "Y02B 30/70"
  ],
  "ipc": [
    "F25B 49/02",
    "H02M 7/538",
    "H02M 7/5381",
    "H02P 27/06"
  ],
  "assignees": [
    "Tecumseh Products Co"
  ],
  "inventors": [
    "James B Farr"
  ],
  "filing_date": "1973-08-20",
  "publication_date": "1975-04-01",
  "grant_date": "1975-04-01",
  "priority_date": "1972-01-03",
  "application_number": "US-38958873-A",
  "family_id": "26909217",
  "cited_by_count": 60,
  "citations": [
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    "US3175167A",
    "US3219906A",
    "US3424961A",
    "US3449922A",
    "US3634701A",
    "US3515967A"
  ]
}