US Patent No. 10,117,292

MEDIUM VOLTAGE HEATER ELEMENTS MOISTURE DETECTION CIRCUIT


Patent No. 10,117,292
Issue Date October 30, 2018
Title Medium Voltage Heater Elements Moisture Detection Circuit
Inventorship Kuldip Tiwana, Hermitage, TN (US)
Assignee CHROMALOX, INC., Pittsburgh, PA (US)

Claim of US Patent No. 10,117,292

1. An electrical heating assembly comprising:one or more medium voltage electrical heating elements that are configured to receive power from a medium voltage power source that supplies between 600 and 38,000 volts to the one or more medium voltage electrical heating elements, wherein the one or more medium voltage electrical heating elements each comprises:
an outer metal sheath;
a resistive wire; and
a dual dielectric core positioned within the outer metal sheath, wherein the dual dielectric core comprises:
a first series of two or more axially-aligned outer tubular dielectric bodies positioned end-to-end, wherein the first series of two or more axially-aligned outer tubular dielectric bodies define a central longitudinal opening and have a first longitudinal axis; and
a second series of two or more axially-aligned inner tubular dielectric bodies having a second longitudinal axis, wherein:
the second series of two or more axially-aligned inner tubular dielectric bodies are positioned end-to-end in the outer metal sheath and are nested at least partially within the central longitudinal opening inside the first series of two or more axially-aligned outer tubular dielectric bodies;
the first longitudinal axis is co-axial with the second longitudinal axis;
the second series of two or more axially-aligned inner tubular dielectric bodies define an interior passageway and the resistive wire is positioned in the interior passageway; and
the second series of two or more axially-aligned inner tubular dielectric bodies are longitudinally staggered relative to the first series of two or more axially-aligned outer tubular dielectric bodies;
a current leakage sensor configured to generate a signal indicative of current leakage from the one or more medium voltage electrical heating elements, wherein the current leakage is proportional to an amount of moisture in contact with the one or more medium voltage electrical heating elements, and wherein the signal is a vector sum of a current flowing through the one or more medium voltage electrical heating elements;
a thyristor coupled to the one or more medium voltage electrical heating elements, wherein the thyristor is configured to control a power level of the one or more medium voltage electrical heating elements; and
a control logic circuit coupled to the thyristor and the current leakage sensor, wherein the control logic circuit is configured to control the one or more medium voltage electrical heating elements and the thyristor based on the signal indicative of the current leakage from the one or more medium voltage electrical heating elements sensed by the current leakage sensor, and wherein the control logic circuit is configured to maintain the one or more medium voltage electrical heating elements at a first power level, in a dry-out mode, while the current leakage detected by the current leakage sensor is proportional to an unacceptable range of moisture in contact with the one or more medium voltage electrical heating elements.