IS200EGDMH1A Exciter Field Ground Detector Module
Description:
IS200EGDMH1A is GE Exciter Field Ground Detector Module. IS200EGDMH1A is a double slot, double height (6U) form factor board that mounts in the Exciter Power Backplane rack (EPBP). A simplex system has one IS200EGDMH1A, while a redundant system has three. IS200EGDMH1A detects field leakage resistance from any point in the field circuit of the generator to ground, either on the ac or dc side. The field ground detector applies a low frequency square wave to the sense resistor connected to the field circuit. EXAM, the attenuator module located in the Auxiliary Panel, senses the voltage across the ground resistor and sends the signal to the EGDM through a nine-conductor cable.
IS200EGDMH1A and EXAM board work together to detect field ground leakage current.

In a redundant system, the set of three IS200EGDMH1A boards are configured as a Controller (C), Master 1 (M1) and Master 2 (M2). The configuration for each IS200EGDMH1A is controlled by a set of program pins on the P2 connector. The C controller receives information from the active DSPX on which EGDM master should provide the drive signal to the sense resistor in the Attenuator Module. The active master receives an Oscillator Signal over the fiber optic link that it converts to a ±50 V signal. This is applied to one end of the sense resistor in the Attenuator Module.

The signal conditioner receives an attenuated (10:1) differential signal from the Sense Resistor. This is a simple unity gain differential amplifier with a high common-mode rejection ratio followed by an A-to-D converter (Voltage Controlled Oscillator VCO). This feeds a fiber-optic transmitter that is cabled to EISB. The signal conditioner circuitry is powered by an isolated power supply to maintain personnel and equipment safety due to the high common-mode voltage at the Sense Resistor. 

Relate items:
IS200EGDMH1AAB
IS200EGDMH1ADE
IS200EGDMH1AFG
IS200EGDMH1AGG