IS200EDCFG1ADC Exciter Dc Feedback Board

The IS200EDCFG1A Exciter DC Feedback Board (EDCF) is used in the EX2100Excitation Control. It measures field current and field voltage at the $CR bridge, and interfaces to the EISB board in the control panel over a high-speed fiber-optic link. The fiber-optics provides voltage isolation between the two boards and high noise immunity. Two fibers are used, one for each signal.

IS200EDCFG1ADC Printed wiring boards may contain static-sensitive components. Therefore, GE ships all replacement boards in antistatic bags.
Use the following guidelines when handling boards:
Store boards in antistatic bags or boxes.
Use a grounding strap when handling boards or board components (per previous Caution criteria).
Note: If three redundant IS200EDCFG1A boards are installed, the exciter can continue running with one board failed. Because of high voltages, it is not possible to replace the failed IS200EDCFG1A online.

 

> To replace the board
1. Make sure that the panel in which the board resides has been de-energized.

2. Open the auxiliary cabinet door, and using equipment designed for high voltages, test any electrical circuits before touching them to ensure that power is off.

3. Carefully disconnect all cables from the IS200EDCFG1A board as follows:

Verify all cables are labeled with the correct connector name (as marked on the board) to simplify reconnection.

Grasp each side of the stab-on connector that joins with the board's stab terminal, El, and gently pull the stab-on connector loose.

Disconnect connectors Pl and Jl6, and fiber-optic connectors CF OF and VF OF.

4. Unlock the push lock pins that hold the EDCF board in the top and bottom slides, and remove the board.

5. Check that the jumpers JPl through Jp9 on the new EDCF board are in the same position as the original board.

6. Orient the new IS200EDCFG1A board in the same position as the one removed, install it in the slides, and lock it in place.

7. Reconnect all cables to the IS200EDCFG1A board as labeled and ensure that cables are properly seated at both ends.

8. Close the auxiliary cabinet door.

 

Field Voltage Feedback:
The field voltage is measured across the negative terminal of the bridge and the positive terminal of the current shunt. After scaling the voltage with the jumpered resistors, the signals are input into a differential amplifier, which controls the voltage-controlled oscillator (VCO).

 

Field Current Feedback:
The field current is measured across a DC shunt at the $CR bridge. This generates alow low-level signal, with a maximum value of 500 mV, which is input to a differential amplifier. The output voltage from the amplifier ranges from -5 V to +5 V into a voltage-controlled oscillator.

 

Power Supply:
Power is supplied to EDCF from an external +24 V dc source. From this, three voltage regulators produce +15 V dc, -15 V dc, and + 5 V dc. The PSOK green LEDs are driven by the +l5 V de output voltages.