System Architecture & Operational Principle
The IS200EHPAG1D (EHPA) is an active, intelligent control board located in the Power Conversion Cabinet, typically mounted on the EBKP backplane or a dedicated sub-chassis near the Power Conversion Modules (PCMs).
Upstream, it receives six low-voltage TTL gate commands from the ESEL (Exciter Selector/Sequence) board via shielded twisted-pair cables. These signals are optically isolated and AC-coupled on entry to protect the low-voltage logic from bridge transients.
Internal Processing, an onboard Intel Celeron 650MHz processor running QNX (Real-Time OS) manages the firing algorithms. An onboard DC/DC converter takes the 125V DC input (via EPDM) and regulates it to support gate drive across a wide range (14-32V DC). It features 6 Independent Gate Pulse Amplifiers, each driving one SCR/thyristor on the power bridge with galvanic isolation between gates.
Downstream/Monitoring, it interfaces with EXCS (Current Sensors) via J9/J10 to monitor phase current (Hall Effect), connects to RTD/Thermistors (J13) for bridge temperature, and accepts Fan Tach inputs (J12) for cooling validation. If thresholds are exceeded (Overtemp/Fan Fail), the EHPA can inhibit firing to protect the hardware. Status is indicated via front-panel LEDs (Power, Gate In/Out, Current, Temp, Fan, Fault).
Core Technical Specifications
- Functional Acronym: EHPA (Exciter High Power Amplifier)
- Processor: Intel Celeron 650 MHz
- Memory: 128 MB SDRAM
- Operating System: QNX (Real-Time)
- Input Voltage: 14 to 32 V DC (Sourced from 125V DC EPDM externally stepped down)
- Gate Drive: 6 Independent Channels (Optically Isolated Inputs & Galvanically Isolated Outputs)
- Max Lead Resistance: 15 Ω (Gate wiring)
- SCR Driving Capability: Up to 6 SCRs (Dedicated GPA per device)
- Sensor I/O: J9/J10 (EXCS Current Feedback), J12 (Fan Tach), J13 (RTD/Temp Switch)
- Configuration: Jumper Selectable (JP2 for Fan Mode, Temp Source Select, etc.)
- Indicators: LEDs for PWR, Gate In (6x), Gate Out (6x), Bridge Current, Temp, Fan, Filter, Fault
- Operating Temp: 0°C to +70°C
- Technology: Surface Mount
