Description
Key Technical Specifications
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Model Number: 9905-092K
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Manufacturer: Woodward
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Supply Voltage: 12, 24, or 32 VDC (10 V min – 45 V max)
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Sensor Feed: 50 mA @ 12 or 24 VDC for external 2-wire transmitters
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Output Options: Low-signal select, high-signal select, difference, load control (DIP selectable)
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Isolation: 500 V input-to-output, opto-coupled
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Accuracy: ±0.5 % of span over –40 °C to +71 °C
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Update Rate: 10 ms (output follows input in <20 ms)
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Connectors: Pluggable 6-position terminal strip (line, load, sensor, common)
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Dimensions: 8.5″ H × 2″ W × 7″ D
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Mounting: DIN-rail or panel; no fan required
Woodward 9905-092K
Field Application & Problem Solved
Cogeneration sites live or die on import/export control. Feed the utility too much and the inter-tie relay trips; suck too much and you eat demand charges. The 9905-092K sits between the utility meter and the Woodward 2301A/505 speed control and biases the speed reference so the generator nails a precise kW set-point. I usually land the utility CT/PT on the input terminals, take the 0–5 V bias output into the 2301A “AUX INPUT,” and set the DIP switches for “low-signal select.” One rotary sets dead-band (0.5–5 %), another sets gain (0–20 %). Result: turbine drifts ±1 kW instead of ±50 kW, and the utility never sees a swing big enough to bill demand. You’ll find this card on landfill-gas gensets, small steam turbines, and any island-mode system that parallells with the grid.
Cogeneration sites live or die on import/export control. Feed the utility too much and the inter-tie relay trips; suck too much and you eat demand charges. The 9905-092K sits between the utility meter and the Woodward 2301A/505 speed control and biases the speed reference so the generator nails a precise kW set-point. I usually land the utility CT/PT on the input terminals, take the 0–5 V bias output into the 2301A “AUX INPUT,” and set the DIP switches for “low-signal select.” One rotary sets dead-band (0.5–5 %), another sets gain (0–20 %). Result: turbine drifts ±1 kW instead of ±50 kW, and the utility never sees a swing big enough to bill demand. You’ll find this card on landfill-gas gensets, small steam turbines, and any island-mode system that parallells with the grid.
Installation & Maintenance Pitfalls (Expert Tips)
Dead-Band Too Tight = Hunting
Rookies set 0.2 % dead-band thinking tighter is better. The loop oscillates and the actuator wears out. Start at 1 % and open up until the bias line sits flat for ten seconds—then lock it.
Rookies set 0.2 % dead-band thinking tighter is better. The loop oscillates and the actuator wears out. Start at 1 % and open up until the bias line sits flat for ten seconds—then lock it.
Use Shielded Twisted Pair for CT/PT
The 50 mA sensor feed is low-level; run unshielded zip cord and you’ll pick up 60 Hz hash that looks like 5 kW error. I run #18 shielded, ground one end only, and keep it out of the 480 V bucket.
The 50 mA sensor feed is low-level; run unshielded zip cord and you’ll pick up 60 Hz hash that looks like 5 kW error. I run #18 shielded, ground one end only, and keep it out of the 480 V bucket.
Verify Polarity Before You Close the Breaker
If the CT polarity is backwards the control thinks import is export and drives the valve the wrong way. Momentarily bump the generator to 5 kW import—bias voltage should go positive; if it goes negative, flip the CT.
If the CT polarity is backwards the control thinks import is export and drives the valve the wrong way. Momentarily bump the generator to 5 kW import—bias voltage should go positive; if it goes negative, flip the CT.
Woodward 9905-092K
Check the DIP Switches After Every Firmware Swap
Woodward 505 downloads reset the aux I/O map. If the mini-switch is still set for “low-signal select” but the software now expects “load bias” you’ll chase phantom offsets for hours.
Woodward 505 downloads reset the aux I/O map. If the mini-switch is still set for “low-signal select” but the software now expects “load bias” you’ll chase phantom offsets for hours.
Technical Deep Dive & Overview
The 9905-092K is an analog summing/selector card built around a low-drift op-amp and an opto-isolated output stage. Two inputs (process and load) feed precision resistors; the DIP array chooses low-signal select, high-signal select, or difference. The winning signal is scaled 0–5 V and sent to the speed control’s auxiliary input. A separate 50 mA current source powers loop-powered transmitters so you don’t need an external supply. The whole loop updates every 10 ms—fast enough to catch step changes in load but slow enough to ignore engine firing noise. No pots, no firmware—just set the switches, torque the terminals, and walk away.
The 9905-092K is an analog summing/selector card built around a low-drift op-amp and an opto-isolated output stage. Two inputs (process and load) feed precision resistors; the DIP array chooses low-signal select, high-signal select, or difference. The winning signal is scaled 0–5 V and sent to the speed control’s auxiliary input. A separate 50 mA current source powers loop-powered transmitters so you don’t need an external supply. The whole loop updates every 10 ms—fast enough to catch step changes in load but slow enough to ignore engine firing noise. No pots, no firmware—just set the switches, torque the terminals, and walk away.
