Apparatus and method for calibrating voltage spike waveforms for three-phase electrical devices and systems

• US 6,847,211 B1
• Filed: 08/26/2003
• Issued: 01/25/2005
• Est. Priority Date: 08/26/2003
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Wilbur, Edward W. Jr., Muhitch, Joseph M.
• Primary Examiner(s): Nolan, Jr., Charles H.
• Application Number:
  US10/652,078
• Time in Patent Office: 518 Days
• Field of Search: 324/601, 324/511
• US Class Current: 324/601
• CPC Class Codes: G01R 31/001 Measuring interference from external sources to, or emission from, the device under test, e.g. EMC, EMI, EMP or ESD testing measuring electromagnetic fields G01R29/08; circuits for generating HV pulses in dielectric strength testing G01R31/14
• CPC Class Codes: G01R 31/2841 Signal generators
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

An apparatus and method for calibrating three-phase voltage spike waveforms used in testing three-phase electrical devices. The apparatus includes a circuit having a plurality of phase voltage lines and a ground line. Phase voltage outputs and a ground output are provided for connection to a device under test. A selection circuit selects one of the phase voltage lines and provides a synchronization voltage signal based on the other lines. A voltage spike generator is joined to the selection circuit for generating a voltage spike waveform synchronized with the voltage signal. Additional circuitry is joined to the voltage spike generator, the phase voltage lines and the outputs which applies the voltage spike waveform across the selected phase voltage line and the ground line.

Claims

1. An apparatus for calibrating voltage spikes used in testing an electrical device, comprising:

a circuit having a plurality of phase voltage lines and a ground line, a plurality of phase voltage inputs and a ground input adapted for connection to a power source, each phase voltage input being connectable to a corresponding phase voltage line and the ground input being connected to the ground line, and a plurality of phase voltage outputs and a ground output adapted for connection to an electrical device under test, each phase voltage output being connected to a corresponding phase voltage line and the ground output being connected to the ground line;

a selection circuit joined to the plurality of phase voltage lines for selecting one of the phase voltage lines and providing a synchronization voltage signal based on voltage signals across the phase voltage lines not selected by the selection circuit;

a voltage spike generator joined to the selection circuit to receive the synchronization voltage signal for generating a predetermined voltage spike waveform based on the synchronization voltage signal; and

additional circuitry joined to the voltage spike generator and the phase voltage lines and joined to said phase voltage outputs and said ground output for applying the predetermined voltage spike waveform across the selected phase voltage line and the ground line.

2. The apparatus according to claim 1 further comprising a capacitive circuit comprising a plurality of capacitor networks joined to the selection circuit, each capacitor network having a variable capacitance such that the capacitor network exhibits any one of a plurality of capacitances, each capacitor network corresponding to a particular phase voltage line.

3. The apparatus according to claim 2 wherein the selection circuit is configured to disconnect the capacitor network corresponding to the selected phase voltage line, connect the capacitor network corresponding to one of the phase voltage lines not selected to the ground line, connect a further one of the capacitor networks corresponding to the remaining phase voltage line not selected to the ground line, and wherein the phase voltage lines that are not selected provide a voltage signal that defines the synchronization signal and has waveform characteristics that are formed by the capacitance exhibited by the capacitor networks corresponding to the phase voltage lines not selected.

4. The apparatus according to claim 2 wherein each capacitor network comprises:

a plurality of capacitors; and

a switch joined to said plurality of capacitors for selectively activating at least one of said plurality of capacitors to provide a resulting capacitance that is to be exhibited by the capacitor network.

5. The apparatus according to claim 4 wherein when the switch selectively activates more than one of said plurality of capacitors, said selectively activated capacitors are connected in parallel.

6. The apparatus according to claim 1 further comprising a monitoring circuit joined to said voltage spike generator for monitoring the predetermined voltage spike waveform.

7. A method for calibrating voltage spikes used in testing an electrical device, comprising:

providing a three-phase electrical device to be tested;

providing a three-phase power source;

providing a circuit having a plurality of phase voltage lines and a ground line;

connecting the phase voltage lines between the three-phase power source and the electrical device under test;

selecting one of the phase voltage lines;

generating a synchronization voltage signal based on voltage signals across the phase voltage lines not selected;

generating a voltage spike waveform based on the synchronization voltage signal, the voltage spike waveform having variable waveform characteristics; and

applying the voltage spike waveform across the selected phase voltage line and the ground line.

8. The method according to claim 7 further wherein the step of generating the voltage spike waveform includes the step of adjusting the waveform characteristics of the voltage spike waveform.

9. The method according to claim 8 further comprising providing a capacitive circuit having a plurality of capacitor networks, each capacitive network having a variable capacitance such that the capacitor network exhibits any one of a plurality of capacitances, each capacitor network corresponding to a particular phase voltage line, and wherein the step of adjusting comprises changing the capacitances of the capacitor networks corresponding to the phase voltage lines not selected.

10. The method according to claim 7 further comprising monitoring the predetermined voltage spike waveform.