Tester for power transformers and capacitors

• US 6,130,530 A
• Filed: 12/22/1997
• Issued: 10/10/2000
• Est. Priority Date: 12/22/1997
• Status: Expired due to Term

• Current Assignee: HD Electric Company (Emerson Electric Company)
• Original Assignee: HD Electric Company (Emerson Electric Company)
• Inventors: McNulty, William J.
• Primary Examiner(s): Ballato, Josie
• Assistant Examiner(s): Solis, Jose M.
• Application Number:
  US08/996,161
• Time in Patent Office: 1,023 Days
• Field of Search: 324/73.1, 324/764, 324/548, 324/546, 324/547, 324/519, 324/537
• US Class Current: 324/73.1
• CPC Class Codes: G01R 15/12 Circuits for multi-testers , i.e. multimeters, e.g. for measuring voltage, current, or impedance at will
• CPC Class Codes: G01R 31/62 Testing of transformers
• CPC Class Codes: G01R 31/64 Testing of capacitors

Abstract

A tester for power transformers and capacitors includes a pulse generator for applying a pulsating test signal to a pair of test leads which may be connected across the terminals of the device to be tested. Also connected across the test leads are a capacitor detector, an inductor detector and a continuity detector. If the connections to the transformer or capacitor in the device to be tested are good, the capacitor detector and inductor detector will distinguish one from the other and indicate that its condition is good. If the connections to the device are not good, the continuity detector will indicate whether there is a short circuit or open circuit condition. The detectors are coupled through control logic circuitry to an indicator circuit including a horn and blinking lights for providing unique indications of capacitor okay, inductor okay, short and open conditions. The capacitor detector provides a discharge path for a capacitor and detects the discharge current flow. The inductor detector responds to the kickback voltage of an inductor, which is of a polarity opposite to that of the input test pulse. The continuity detector measures voltage level to distinguish between impedance levels respectively corresponding to substantially open and substantially short circuit conditions.

Claims

1. Test apparatus for identifying characteristics of a tested device comprising:

a signal generator having test leads across which the tested device may be connected for applying a test signal to the tested device, and

a detection circuit connected across said test leads for sensing the response of the tested device to the test signal,

said detection circuit including a capacitor detector providing a first indication if the tested device is capacitive,

an inductor detector providing a second indication if the tested device is inductive, and

a circuit continuity detector providing a further indication if the tested device is open-circuited or short-circuited.

2. The test apparatus of claim 1, wherein said capacitor detector includes a discharge path and a switch operable in response to discharge of the capacitor through the discharge path.

3. The test apparatus of claim 2, wherein said switch includes a transistor.

4. The test apparatus of claim 2, wherein said capacitor detector includes active circuitry for generating an output signal in response to closing of said switch.

5. The test apparatus of claim 4, and further comprising an indicator circuit coupled to said capacitor detector and providing an indication in response to said output signal.

6. The test apparatus of claim 5, wherein said indicator circuit includes audible and visible annunciators.

7. The test apparatus of claim 2, wherein said signal generator includes a pulse generator for applying a periodic pulse signal to the tested device.

16. The test apparatus of claim 1, wherein said continuity detector includes circuitry for producing a third indication in response to a substantially open circuit connected across said test leads and a fourth indication in response to connection of a substantially short circuit across said test leads.

17. The test apparatus of claim 1, wherein said continuity detector includes circuitry for measuring the level of the voltage across connected terminals of the tested device.

18. The test apparatus of claim 1, and further comprising logic circuitry coupled to said capacitor detector and to said inductor detector and to said continuity detector, and an indicator circuit coupled to said logic circuitry for producing a plurality of indications respectively corresponding to different characteristics of the tested device.

19. The test apparatus of claim 18, wherein said indicator circuit includes audible and visible annunciators.

20. The test apparatus of claim 19, wherein said indicator circuit further includes means for intermittently operating said visible annunciators.

21. The test apparatus of claim 18, wherein said continuity detector has an output and produces a first signal condition at said output if the tested device is open-circuited and a second signal condition at said output if the tested device is short-circuited.

22. The test apparatus of claim 21, wherein said logic circuit responds to an absence of signal from any of the detectors to produce an indication that the tested device is short-circuited.

23. The test apparatus of claim 7, wherein said pulse signal is periodic.

8. Test apparatus for identifying characteristics of a tested device comprising:

a signal generator having test leads across which the tested device may be connected for applying a test signal to the tested device, and

a detection circuit connected across said test leads for sensing the response of the tested device to the test signal,

said detection circuit including a capacitor detector providing a first output signal if the response of the tested device to the test signal indicates that the tested device is capacitive, and

an inductor detector providing a second output signal if the response of the tested device to the test signal indicates that the tested device is inductive.

9. The test apparatus of claim 8, wherein said capacitor detector includes a discharge path and a switch operable in response to discharge of the capacitor through the discharge path.

10. The test apparatus of claim 8, wherein said inductor detector includes a circuit responsive to a voltage of a polarity opposite to that of the test signal for producing said second output signal.

11. The test apparatus of claim 10, wherein said inductor detector includes a transistor switch which is rendered conductive in response to a voltage having a polarity opposite to that of the test signal.

12. The test apparatus of claim 8, and further comprising an indicator circuit coupled to said capacitor detector and to said inductor detector and responsive to said first and second output signals for respectively producing first and second indications.

13. The test apparatus of claim 12, wherein said indicator circuit includes first and second LEDs respectively responsive to said first and second output signals.

14. The test apparatus of claim 13, wherein said indicator circuit further includes an audible annunciator responsive to either of said first and second output signals.

15. The test apparatus of claim 13, wherein said transistor has a base connected in said discharge path for rendering the transistor conductive in the presence of a discharge current in the discharge path.