Ground monitor

• US 8,692,557 B2
• Filed: 06/19/2013
• Issued: 04/08/2014
• Est. Priority Date: 06/03/2010
• Status: Active Grant

• Current Assignee: Lear Corporation
• Original Assignee: Lear Corporation
• Inventors: Hein, David A., Khan, Aftab Ali
• Primary Examiner(s): PATEL, PARESH H
• Application Number:
  US13/921,234
• Publication Number:
  US 20130278271A1
• Time in Patent Office: 293 Days
• Field of Search: None
• US Class Current: 324/505
• CPC Class Codes: B60L 3/0023 Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train
• CPC Class Codes: B60L 53/14 Conductive energy transfer
• CPC Class Codes: G01R 19/145 Indicating the presence of current or voltage
• CPC Class Codes: G01R 27/18 Measuring resistance to earth , i.e. line to ground
• CPC Class Codes: G01R 27/20 Measuring earth resistance; Measuring contact resistance, e.g. of earth connections, e.g. plates
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

A ground monitor is disclosed. The ground monitor may be configured to conduct a ground continuity test based on a determined ground resistance. The ground monitor may be operable to determine the ground resistance as a function of a voltage differential detected during application of a test current.

Claims

1. A ground monitor being operably coupled to a three-pronged outlet having a hot plug, a neutral plug, and a ground plug of an AC power network to detect a ground resistance of the network based on a voltage differential between the neutral plug and the ground plug of the outlet, the ground monitor comprising:

a signal generator operable to apply a test current to the neutral plug at a first frequency, wherein the hot plug of the outlet receives a current flowing therethrough at a second frequency and the first frequency is different from the second frequency;

a filter being operable to remove signals having the second frequency and to output a filtered signal; and

a voltage sensor operable to measure a voltage differential between the neutral and ground plugs based on the filtered signal, the voltage differential representing the ground resistance during application of the test current.

2. The ground monitor of claim 1 further comprising a frequency sensor operable to sense the second frequency of the current flowing to the hot plug and a controller operable with the frequency sensor to select the first frequency of the test current to be different from the second frequency.

3. The ground monitor of claim 2 wherein the controller is further operable in a frequency test mode during which the test current is applied at a plurality of frequencies and to select the first frequency to be the one of the plurality of frequencies resulting in a highest quality measurement of the voltage differential.

4. The ground monitor of claim 3 wherein the controller, during the frequency test mode, being further operable to also vary an amplitude of the test current for each of the plurality of frequencies, the controller being further operable to detect the varying amplitudes of the test current when determining the highest quality measurement.

5. The ground monitor of claim 4 wherein the controller being further operable to determine the voltage variation induced at each of the varying amplitudes and selecting the highest quality measurement to correspond with the one of the plurality of frequencies where the voltage variations substantially correlates with the varying amplitudes.

6. The ground monitor of claim 1 wherein the signal generator continuously applies the test current while the terminals are connected to the neutral and ground plugs.

7. The ground monitor of claim 1 wherein the signal generator applies the test current in moments in which the current flowing through the hot plug is at a zero-crossing.