Leakage current cancellation device

• US 6,388,451 B1
• Filed: 08/16/2000
• Issued: 05/14/2002
• Est. Priority Date: 08/16/2000
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Minck, Robert W., Burba, Joseph Carl
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Deb, Anjan K.
• Application Number:
  US09/640,484
• Time in Patent Office: 636 Days
• Field of Search: 324/509, 324/521, 324/522, 324/720, 324/763, 323/273, 323/356, 323/315
• US Class Current: 324/522
• CPC Class Codes: B60L 3/0069 relating to the isolation, e.g. ground fault or leak current
• CPC Class Codes: B60L 53/30 Constructional details of charging stations
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• 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 system (20, 30, 40, 50) and method for canceling a leakage current is provided that uses line voltages (L1, L2) that are out of phase with each other to produce a counter leakage potential that cancels leakage current. In one embodiment of the invention, the actual potential of the phases is measured (42, 52, 54) and used to determine the counter potential that is to be applied to the line voltage (L1 or L2) that is generating the leakage current. The counter potential is applied to the appropriate line voltage by way of a transistor circuit (Q1, Q2). The transistor circuit (Q1, Q2) is controlled through standard electronic circuitry (28), or by way of a microprocessor device (32).

Claims

1. A leakage current cancellation device for an electric vehicle comprising:

a differential transformer having a first line voltage and a second line voltage passing therethrough, said first and second line voltages being out of phase with each other, said differential transformer having a sense winding whereby a leakage current produces a current imbalance in said differential transformer, said current imbalance produces a potential across said sense winding;

a safety ground;

means for controlling first and second transistors, said first transistor being connected to said second line voltage and said second transistor being connected to said first line voltage, said first and second transistors being connected to said safety ground;

whereby said first transistor becomes conductive when said leakage current is generated from said first line voltage thereby inducing a reverse potential to said safety ground, and said second transistor becomes conductive when said leakage current is generated from said second line voltage thereby inducing a reverse potential to said safety ground.

2. The device as claimed in claim 1 wherein said means for controlling said first and second transistors is a differential amplifier.

3. The device as claimed in claim 1 wherein said means for controlling said first and second transistors is a microprocessor.

4. The device as claimed in claim 1 wherein said first and second transistors are optically isolated field effect transistors.

5. The device as claimed in claim 1 wherein said leakage current cancellation device is located on the electric vehicle.