IS200EGPAG1A - Exciter Gate Pulse Amplifier Board

SPECIFICATIONS:

Part Number: IS200EGPAG1A
Manufacturer: General Electric
Series: EX2100
Product Type: Exciter Gate Pulse Amplifier Board
Operating System: QNX
Power Requirements: +5 V dc, 6 A
Number of input channels: 24
Trip Solenoid Rating: 125 V dc
Power supply voltage: 28 V dc
Operating temperature: 40 to 70°C
Size: 168 x 150 x 55 mm
Repair: 3-7 Days
Availability: In Stock
Country of Origin: United States
Manual: GEI-100461A

FUNCTIONAL DESCRIPTION:

IS200EGPAG1A is an Exciter Gate Pulse Amplifier Board manufactured and designed by General Electric as part of the EX2100 Series used in GE Excitation Turbine Control Systems. The Power Conversion cabinet contains the Power Conversion Module (PCM), the Exciter Gate Pulse Amplifier (EGPA) board, the ac circuit breaker, and the dc circuit contactor. Three-phase power for the PCM comes from a PPT external to the exciter. The ac supply comes into the cabinet through the ac circuit breaker (if supplied), and is filtered by 3-phase line filters in the auxiliary cabinet. The EGPA board interfaces the control to the Power Bridge. EGPA takes the gate commands from the ESEL board in the controller and generates the gate firing pulses for six SCRs (Silicon Controlled Rectifiers). It is also the interface for current conduction feedback, and bridge airflow and temperature monitoring. On a new exciter, an RTD is used to monitor the temperature and generate alarms instead of the Klixon switches. Additional switches actuated by fan rotation monitor cooling air flow across the bridge. On an exciter controls only retrofit, the exciter may have provisions for accepting feedback from two thermal switches mounted on the SCR heatsink assemblies. One thermal switch opens at the alarm level (170 °F (76 °C)) and the other at the trip level (190 °F (87 °C)). These switches are wired to the EGPA board and may require retrofitting into the existing bridge. If either switch opens, a bridge overtemperature alarm is generated. If both switches open, a fault and a trip are generated.

BRIDGE RECTIFIER:

Each bridge rectifier is a 3-phase full-wave thyristor bridge. The bridge has six SCRs (thyristors) controlled by the Exciter Gate Pulse Amplifier board (EGPA) as shown in Figure 2-3. Heat is dissipated through large aluminum cooling fins and forced air flow from overhead fans.

LEG REACTORS AND CELL SNUBBERS:

The commutating reactors are located in the ac legs feeding the SCRs, and the snubbers are an RC circuit from the anode to the cathode of each SCR. The cell snubbers, line-to-line snubbers, and line reactors together perform the following functions to prevent misoperation of the SCRs.

• Limit the rate of change of current through the SCRs and provide a current dump to aid in starting conduction.
• Limit the rate of change in voltage across the cell and, during cell commutation, limit the reverse voltage that occurs across the cell.

The SCR snubbers include PRV resistors to limit the peak reverse voltage. These resistors can be removed if required. Three-phase input power is fed to the bridge from the secondary of the PPT, either directly or through an ac breaker or disconnect, and a line-to-line filter. With inverting bridge designs, the bridge is capable of negative forcing voltage, which provides fast response for load rejection and de-excitation. The DC output of the bridge is fed through a shunt, and on some designs, a contactor (41A or both 41A and 41B) to the generator field. The bridge design utilizes DC leg fuses to protect the SCRs from overcurrent.

SHAFT VOLTAGE SUPPRESSOR:

Excitation systems, which produce a dc voltage from ac through a solid-state rectification process, produce ripple and spike voltages at the exciter output. Due to their rapid rise and decay times, these voltages are capacitively coupled from the field winding to the rotor body. This creates a voltage on the shaft relative to ground. Shaft voltage, if not effectively controlled, can be damaging to both journals and bearings. The shaft voltage suppressor is a filter that conducts the high-frequency components of the induced voltages to ground. (This filter is shipped loose in some cases; it is part of the lineup.

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FREQUENTLY ASKED QUESTIONS:

What is IS200EGPAG1A?

The IS200EGPAG1A is an Exciter Gate Pulse Amplifier (EGPA) Board manufactured by General Electric as part of the EX2100 Series. It generates gate firing pulses for six SCRs in the exciter bridge and interfaces with the ESEL controller board. The board also monitors current conduction, airflow, and temperature of the bridge to ensure safe and efficient operation. It is compatible with GE Excitation Turbine Control Systems.

How does the IS200EGPAG1A interface with the exciter bridge?

The EGPA board receives gate commands from the ESEL controller and generates firing pulses for six SCRs in the bridge rectifier. It monitors bridge current conduction, airflow, and thermal feedback from RTDs or thermal switches. The board ensures SCR operation is synchronized and protected against overcurrent and overtemperature conditions.

What protection features are included on the IS200EGPAG1A?

The board works with SCR snubbers, PRV resistors, and leg reactors to limit current and voltage transients, preventing misoperation of the SCRs. It also interfaces with thermal switches or RTDs to provide overtemperature alarms and trips. Additionally, the shaft voltage suppressor filters high-frequency voltages to protect generator bearings.