Description
DS3820RDMA1A1A Product Overview
The DS3820RDMA1A1A is a relay-driver and digital I/O printed-circuit board used inside GE Mark IV and Mark V Speedtronic turbine-control cubicles. It occupies a 6U VME64 card slot and acts as the high-current interface between the microprocessor and the external contactors, solenoids, and status relays that switch motor power, reactor banks, or auxiliary systems.
The DS3820RDMA1A1A is a relay-driver and digital I/O printed-circuit board used inside GE Mark IV and Mark V Speedtronic turbine-control cubicles. It occupies a 6U VME64 card slot and acts as the high-current interface between the microprocessor and the external contactors, solenoids, and status relays that switch motor power, reactor banks, or auxiliary systems.
In the automation hierarchy the card sits at the “coil-drive & status” layer: it receives 24 V logic commands from the CPU, sources or sinks up to 500 mA per bit (field-fused), and returns discrete feedback (coil-energized / coil-open) over the same 64-bit data path. Transformer isolation on each output keeps the 125 VDC battery ground separate from the 5 V logic ground, so ground-shift events during breaker closures do not propagate into the sensitive control backplane.
The board is part of the DS3820 “RDMA” family of Mark IV/V personality boards—cards that share the same mechanical envelope and 96-pin edge connector but perform dedicated relay or digital functions. Using a common hardware platform allows plant stores to stock one spare chassis and populate it with the exact personality boards required for each turbine section
GE DS3820RDMA1A1A
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Technical Specifications
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Model Number: DS3820RDMA1A1A
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Manufacturer: General Electric
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Product Type: Relay-Drive & Digital I/O Module
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I/O Count: 64 bits, configurable as input or output per 8-bit nibble
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Output Drive: 24 VDC, 500 mA sink/source per bit (field-fused)
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Isolation: Transformer-coupled, 1.5 kV working between field and logic
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Data Interface: VME64 slave, A16/A24, D16/D32 transfers
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Status: On-board BIT LED (red = fault, green = ready)
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Connectors: 96-pin DIN edge finger (backplane), no external field terminals
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Power: +5 V @ 3 A typical (logic), +24 V @ 8 A max (field side)
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Weight: 1.45 lbs (0.66 kg)
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Operating Temperature: 0 … +70 °C (card ambient)
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Storage Temperature: -40 … +85 °C
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Vibration/Shock: 5 g / 50 g (per Mark IV cabinet spec)
Core Features & Customer Value
High-current relay drive – Each bit can sink or source 500 mA at 24 V, enough to energize lock-out relays, solenoid valves, or small contactors directly—no external interposing relays required, saving panel space and wiring.
High-current relay drive – Each bit can sink or source 500 mA at 24 V, enough to energize lock-out relays, solenoid valves, or small contactors directly—no external interposing relays required, saving panel space and wiring.
Transformer isolation – 1.5 kV working isolation between field and logic means the 125 VDC battery ground can shift ±40 V during breaker closures without corrupting the 5 V CPU bus, improving uptime and reducing nuisance faults.
64-bit density – One card replaces four 16-bit driver boards, freeing VME slots for additional I/O and simplifying the spare-parts list.
On-board BIT – The front-panel LED turns red if any output is shorted or any input is open, so during commissioning you can spot a failing coil immediately without metering each pin at the terminal strip.
Drop-in spare – Shares the same DS3820 form factor as earlier RDMA revisions; no mounting changes, no parameter downloads, and no calibration required during swap-out.
GE DS3820RDMA1A1A
Typical Applications
In combined-cycle plants the DS3820RDMA1A1A is installed in the “auxiliary drive” bay of every Mark IV or Mark V panel that governs gas turbines, boiler-feed pumps, or induced-draft fans. It drives the 24 VDC coils of lock-out relays, cooling-fan contactors, and fire-protection dampers while riding out battery transients during breaker closures.
In combined-cycle plants the DS3820RDMA1A1A is installed in the “auxiliary drive” bay of every Mark IV or Mark V panel that governs gas turbines, boiler-feed pumps, or induced-draft fans. It drives the 24 VDC coils of lock-out relays, cooling-fan contactors, and fire-protection dampers while riding out battery transients during breaker closures.
In pipeline compressor stations the same board feeds the Mark IV overspeed protection system that energizes 125 VDC trip solenoids through external interposing relays; the 24 V auxiliary rail energizes the relay coil, so loss of the RDMA card forces an automatic shutdown.
Because the card is passive (no firmware) it is also accepted in nuclear standby turbine-generator sets, where “simple device” classification avoids additional software V&V.
