Sensitive DC Current Imbalance Detector And Calibration Method

Abstract

A current leakage detector for detecting current leakage between a power source and a load including a first sensing coil and a second sensing coil positioned opposite the first sensing coil. The current leakage detector further includes a magnetic field sensor proximate the first sensing coil and the second sensing coil and the magnetic field sensor has a response range. The current leakage detector also includes a bias circuit configured to adjust the response range of the magnetic field sensor. A method for detecting current leakage includes providing a first sending coil and a second sensing coil. The method continues with the steps of providing a magnetic field sensor in proximity to the first and second sensing coils and providing a bias circuit. The method continues with the step of utilizing the bias circuit to place the response of the magnetic field sensor within a preferred response range.

What is claimed is: 
     
         1 . A current leakage detector for detecting current leakage between a power source and a load, the current leakage detector comprising
 a first sensing coil;   a second sensing coil positioned opposite the first sensing coil;   a magnetic field sensor proximate the first sensing coil and the second sensing coil, wherein the magnetic field sensor has a response range; and   a bias circuit configured to adjust the response range of the magnetic field sensor.   
     
     
         2 . The current leakage detector of  claim 1 , wherein the magnetic field sensor is a giant magneto-restrictive sensor. 
     
     
         3 . The current leakage detector of  claim 1 , wherein the bias sensor circuit comprises:
 a control unit;   a bias coil driver operably connected to the control unit; and   a bias coil driven by the bias coil driver.   
     
     
         4 . The current leakage detector of  claim 3 , wherein the bias sensor circuit further comprises:
 a sensor amplifier, wherein the sensor amplifier is operably connected to the magnetic field sensor; and   a sensor analog-to-digital converter.   
     
     
         5 . An electrically powered device comprising:
 a power supply;   a load; and   a current leakage detector for detecting current leakage between the power supply and the load, the current leakage detector comprising   a first sensing coil;   a second sensing coil positioned opposite the first sensing coil;   a magnetic field sensor proximate the first sensing coil and the second sensing coil, wherein the magnetic field sensor has a response range; and   a bias circuit configured to adjust the response range of the magnetic field sensor.   
     
     
         6 . The electrically powered device of  claim 5 , wherein the magnetic field sensor of the current leakage detector is a giant magneto-restrictive sensor. 
     
     
         7 . The electrically powered device of  claim 5 , wherein the bias sensor circuit comprises:
 a control unit;   a bias coil driver operably connected to the control unit; and   a bias coil driven by the bias coil driver.   
     
     
         8 . The electrically powered device of  claim 5 , wherein the bias sensor circuit of the current leakage detector further comprises:
 a sensor amplifier, wherein the sensor amplifier is operably connected to the magnetic field sensor; and   a sensor analog-to-digital converter.   
     
     
         9 . The electrically powered device of  claim 5 , wherein the load is an electric motor. 
     
     
         10 . A method for detecting current leakage between a power source and a load connected to the power source, the method comprising the steps of:
 providing a first sensing coil between the power source and the load;   providing a second sensing coil in an opposing position to the first sensing coil between the load and the power source;   providing a magnetic field sensor in proximity to the first and second sensing coils;   providing a bias circuit; and   utilizing the bias circuit to place the response of the magnetic field sensor within a preferred response range.   
     
     
         11 . The method of  claim 10 , wherein the step of providing a bias circuit further comprises:
 providing a bias coil;   providing a bias coil driver to drive the bias coil; and   providing a control unit to control the operation of the bias coil.   
     
     
         12 . The method of  claim 11 , wherein the step of utilizing the bias circuit further comprises the steps of:
 measuring the magnetic field produced by the bias coil with the magnetic field sensor; and   adjusting the current applied to the bias coil to find the minimum voltage output by the magnetic field sensor.   
     
     
         13 . The method of  claim 12 , wherein the step of utilizing the bias circuit further comprises the step of adjusting the current applied to the bias coil to find the maximum voltage output by the magnetic field sensor. 
     
     
         14 . The method of  claim 13 , wherein the step of utilizing the bias circuit further comprises the step of adjusting the current applied to the bias coil to a point at which the voltage produced by the magnetic field sensor is a median value between the minimum voltage output by the magnetic field sensor and the maximum voltage output by the magnetic field sensor. 
     
     
         15 . The method of  claim 14 , wherein the step of utilizing the bias circuit further comprises applying an initial bias current to the bias coil before the power source is connected to the load. 
     
     
         16 . The method of  claim 10 , further comprising the step of identifying a current leakage condition. 
     
     
         17 . The method of  claim 16 , wherein the step of identifying a current leakage condition comprises identifying a magnetic field imbalance between the first and second sensing coils. 
     
     
         18 . The method of  claim 16 , wherein the method further comprises the step of providing an alert when a current leakage condition is detected. 
     
     
         19 . The method of  claim 16 , wherein the method further comprises the step of automatically disconnecting the power source from the load in response to the detection of a current leakage condition. 
     
     
         20 . The method of  claim 10 , further comprising the step of identifying a current leakage condition after the step of utilizing the bias circuit to place the response of the magnetic field sensor within a preferred response range.