Three phase primary power regulator

• US 3,996,508 A
• Filed: 11/20/1972
• Issued: 12/07/1976
• Est. Priority Date: 11/20/1972
• Status: Expired due to Term

• Current Assignee: Northrop Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Corporation (Northrop Grumman Corporation)
• Inventors: Board, Ralph
• Primary Examiner(s): Pellinen, A. D.
• Application Number:
  US05/308,147
• Time in Patent Office: 1,478 Days
• Field of Search: 317/31, 317/33 VR, 321/5, 321/18, 323/6, 323/8, 323/22 T, 323/44 R, 323/62
• US Class Current: 323/277
• CPC Class Codes: G05F 1/30 semiconductor devices only

Abstract

A regulated three phase power supply with a wye connected, isolated neutral transformer having a full wave three phase bridge connected between the phase windings and the common point. A clipper transistor is connected across the bridge so that each phase current flows through the transistor. A drive circuit for the clipper transistor is isolated from ground. Reducing the drive to the clipper transistor increases its impedance and clips the voltage wave across the transformer primary. An output circuit is connected with the transformer. A three phase feedbck circuit is connected from either the output circuit or the wye connected circuit to the clipper transistor and is responsive to the instantaneous phase voltages to increase the transistor impedance, clipping the input voltage, when the sensed condition is excessive.

Current regulation is provided by increasing the drive to the transistor as the current through it increases. Overload and overvoltage sensing circuits increase the impedance of the clipping transistor in the event of an overload or transient overvoltage condition. A combination of delta and wye three phase, full wave rectified feedback circuits provide six phase feedback and a high efficiency of control. Plural outputs may be obtained from the transformer; and delta and wye output circuits can be connected to increase the ripple frequency.

Claims

1. A three phase primary power regulator, comprising:

a source of three phase power;

means defining a common ground reference potential;

three impedance elements connected with said source, forming a three phase, wye connected circuit, each impedance element having its neutral terminal isolated from the neutral terminals of the other impedance elements and from said reference potential means;

a three phase full wave diode bridge circuit connected with the neutral terminals of said wye connected impedance elements and isolated from said reference potential means;

a variable impedance device having an impedance which is generally continuously variable from a low value to a high value in accordance with a control voltage applied thereto, connected with said three phase bridge circuit and in series with said elements across said source;

an output circuit for deriving energy from said impedance elements; and

a feedback circuit, isolated from said reference potential means, responsive to voltage across said impedance elements to control the impedance of said variable impedance device between said low value and said high value to regulate the energy derived in the output circuit, maximum energy being derived when the impedance of the device is low, and the peaks of voltage and current of each of the three power phases from said source being clipped as the impedance of the device increases from the low value to the high value.

2. The primary power regulator of claim 1 in which said feedback circuit is connected from the output circuit to said variable impedance device.

3. The primary power regulator of claim 1 in which said feedback circuit is connected from said impedance elements to said variable impedance device.

4. The primary power regulator of claim 1 in which said impedance elements form the primary windings of a three phase transformer.

5. The primary power regulator of claim 1 in which said impedance elements have the primary windings of a three phase transformer connected in parallel therewith.

6. The primary power regulator of claim 1 having two three phase feedback circuits, one displaced in phase from the other, to provide six phase limiting of the voltage to said output circuit.

7. The primary power regulator of claim 1 including means responsive to excessive current through said variable impedance device to limit the voltage to said output circuit.

8. The primary power regulator of claim 1 including means responsive to excessive voltage from said source, connected to said variable impedance device to limit the voltage to said output circuit.

9. The primary power regulator of claim 1 in which said feedback circuit includes a voltage reference, means for comparing the instantaneous feedback voltage with said reference, and means for increasing the impedance of said device to limit the voltage to the output circuit when the feedback voltage exceeds said reference.

10. The primary power regulator of claim 1 in which said variable impedance device is a variable impedance transistor connected across said three phase bridge circuit, and in which said feedback includes a base drive circuit for the transistor, responsive to voltage across the impedance elements, increasing the impedance of said transistor, as a function of the voltage, to limit the output voltage.

11. The primary power regulator of claim 10 in which said feedback circuit is in phase with the source, providing phase-to-phase clipping.

12. The primary power regulator of claim 10 in which said feedback circuit includes a wye-to-delta transformer, providing phase-to-neutral clipping.

13. The primary power regulator of claim 10 having two feedback circuits, one in phase with the source, providing phase-to-phase clipping, and the other including a wye-to-delta transformer, providing phase-to-neutral clipping.

14. The primary power regulator of claim 1 having a plurality of output circuits connected with said impedance elements, in which said feedback circuit is connected from only one of the output circuits to said variable impedance device, regulating the voltage to all of the output circuits.

15. The primary power regulator of claim 14 in which one of said output circuits is wye connected and another of the output circuits is delta connected, the regulator also including two full wave rectifiers, one connected with each output circuit, and means connecting the outputs of said full wave rectifiers together, affording a combined output with an effective ripple frequency six times the source frequency.

16. The primary power regulator of claim 10, wherein the feedback circuit includes a source of operating potential connected with said transistor and a circuit for applying a potential to the base of the transistor to cause it to conduct, means establishing a reference potential and means responsive to the voltage across said impedance elements and to said reference to change the potential at the base of said transistor, increasing its impedance, limiting the instantaneous voltage to the output.

17. The primary power regulator of claim 16 wherein said source of operating potential includes a three phase full wave rectifier connected with the output circuit and having the emitter-collector circuit of said transistor connected thereacross.

18. The primary power regulator of claim 1 in which said variable impedance device is a clipping transistor having an emitter-collector circuit connected in a series with said bridge circuit, said regulator further including means applying a potential to the base causing the transistor to conduct, and means responsive to current flow through said transistor to vary the potential of the base and modify the transistor impedance.

19. The primary power regulator of claim 18 in which a resistor is connected in series with said clipping transistor and the means responsive to current flow is connected across the resistor and is responsive to the voltage developed by the current flowing therethrough.

20. The primary power regulator of claim 19 in which the means responsive to the voltage across said resistor includes a differential transistor amplifier having two transistors with a common emitter resistor, the bases of the transistors being connected across the resistor in series with the clipping transistor, and means responsive to the current through one of said differential transistors for varying the base potential of said clipping transistor in accordance with the current therethrough.

21. The primary power regulator of claim 1 in which said variable impedance device is a clipping transistor having an emitter collector circuit connected in series with said bridge circuit and a base drive circuit connected with the base of said clipping transistor to control its impedance and the current flow therethrough, said circuit further including means sensing an abnormal electrical condition and connected with said base drive circuit to increase the impedance of said clipping transistor upon the occurrence of such abnormal condition.

22. The primary power regulator of claim 21 wherein said sensing means includes a sensing transistor having its output connected with the base drive circuit of the clipping transistor and normally nonconducting, said sensing transistor having its input connected with means responsive to the source voltage and to the clipping transistor current, said sensing transistor being rendered conductive by abnormal source voltage or clipping transistor current, to reduce the drive to the clipping transistor.

23. The primary power regulator of claim 2 in which said feedback circuit is DC isolated from said output.

24. The primary power regulator of claim 23 in which said feedback circuit is AC coupled to said output.

25. The primary power regulator of claim 23 in which said output circuit includes an AC to DC rectifier, and said feedback circuit includes an energy transducer responsive to DC for coupling a signal to said variable impedance device.

26. The primary power regulator of claim 5 including switch means connecting the primary winding of the three phase transformer to said impedance elements.

27. The primary power regulator of claim 26 including an oil filled transformer housing having the primary windings for a plurality of transformers therein, six terminals on said housing connected with the terminals of said three impedance elements, and switch means in said housing connecting said transformer windings with said terminals, and wherein said feedback circuit is connected to said impedance elements.

28. The primary power regulator of claim 27 in which said feedback circuit includes means for adjusting the level of energy regulation of said variable impedance device.

29. The primary power regulator of claim 1 including means for adjusting the level of energy regulation of said variable impedance device.

30. The primary power regulator of claim 9 including means for adjusting the relationship between the voltage reference and the feedback voltage to control the level of energy regulation of said variable impedance device.