US 5,508,606 AGranted

Direct current sensor

AssigneeEaton Corporation

InventorLawrence J. Ryczek

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Abstract

Direct current can be measured by passing a conductor carrying the current through the core of a toroidal transformer having a bias winding and a sensing winding. A pulse generator send pulses of magnetization current through the sensing winding so that the magnetization current produces a magnetic flux in the core which opposes a magnetic flux produced by the direct current carried by the conductor. A sensing circuit, connected to the sensing winding, detects the level of current through that winding to produce a measurement of the direct current carried by the conductor. A constant direct current is applied through the bias winding to increase the magnetic flux produced by the direct current carried by the conductor. Biasing the magnetic flux enables even small currents flowing through the conductor to be measured. Another version of the current sensor uses two transformers to measure direct current flowing in either direction in the conductor and provides an indication of that current's polarity.

Claims9

Dependent claims

A direct current sensor comprising:

a transformer having an annular core of magnetic material through which passes a conductor carrying a direct current to be sensed, a bias winding wound on the annular core, and a sensing winding wound on the annular core;
a source of magnetization current coupled to the sensing winding of said transformer wherein the magnetization current is applied as pulses to the sensing winding so that the magnetization current produces in the annular core a magnetic flux which opposes a magnetic flux produced by the direct current carried by the conductor;
a sensing circuit connected to the sensing winding of the transformer and responding to current flowing through the sensing winding by producing a signal that indicates a magnitude of the direct current carried by the conductor;
and
a direct current source connected to the bias winding for applying a bias direct current of a substantially constant magnitude to the bias winding, wherein the bias direct current produces in the annular core a magnetic flux which increases the magnetic flux produced by the direct current carried by the conductor.

2 more elements

Dependencies are inferred from the claim text.