Power Corporation of America

Michalek Engineering Group, Inc.

Ebrahim B Shahrodi

Jan K Michalek

The present invention involves measurement of an electrical current by means of a current transformer having the current to be measured passing in an axial direction through the current transformer, and the voltage induced thereby in the windings of the current transformer are used to produce a first voltage. A Hall effect is used in series with the current transformer to produce a second voltage measurement corresponding to the current measured by the Hall effect sensor. When the two measurements agree to within a predetermined value (typically 5% of the root-mean-square current values measured by each sensor) then the current transformer reading is used as the more accurate. Otherwise, the Hall effect current sensor is used as the more accurate current measurement.

Method and apparatus for measurement of AC and DC electrical current

A solid state, bipolar, ignition exciter for gas turbine engines is described for delivering high energy pulses to one or more igniter plugs. A storage capacitor is charged with typically 12 to 20 Joules of stored energy and discharged through a solid state switch and a series-connected ignitor plug. The solid state switch consists of a plurality of silicon controlled rectifiers (SCRs) connected in series, in combination with other components connected in parallel with each SCR. Protection is provided against transients in voltage by means of resistance-capacitance snubber circuits connected in parallel with each SCR. Protection is provided against transients in current by means of inductance connected externally, and in series with, the solid state switch. Protection is provided against damage from reverse voltages by means of a reverse current path through the solid state switch, typically by means of a diode or series-connected diode chain connected in parallel with the SCRs. Thus, the solid state switch of the present invention conducts current alternately in forward and reverse directions once the SCRs are switched to their conducting state, providing bipolar current flow to the igniter plug. Controlling means and short circuit protection circuits are also described.

Growing community of inventors

Newark, OH, United States of America

Ebrahim B Shahrodi