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Woodward 9907-838 – Load Sharing Module with PWM Output
Product Overview
The Woodward 9907-838 is a Load Sharing Module designed for generator-set applications using engines equipped with Caterpillar digital speed controls that accept a pulse-width-modulated (PWM) input. It provides both isochronous and droop load-sharing functions, allowing generator sets to share electrical load while maintaining coordinated engine-speed control. The module operates from a 24 VDC supply and includes PWM output surge protection, which distinguishes it from the closely related 9907-175. Woodward documentation also identifies compatibility with accessories such as SPM-A synchronizers, paralleling controls, and automatic generator loading systems.
Technical Specifications — 9907-838
| Parameter | Value |
|---|---|
| Product Model | 9907-838 |
| Manufacturer | Woodward |
| Product Type | Load Sharing Module |
| Application | Generator set load sharing |
| Control Type | PWM |
| Supply Voltage | 24 VDC |
| PWM Output | 500 ± 100 Hz |
| PWM Output Protection | Surge protected |
| Load Sharing | Isochronous / Droop |
| Droop Adjustment | 0–9% speed reduction |
| Load Gain Adjustment | Approx. 3–7 Arms full-load range |
| Operating Temperature | -40 to +70°C |
| Dimensions (L × W × H) | Approx. 273.6 × 214.1 × 59.2 mm |
| Weight | Approx. 1.397 kg |
| Mounting | Generator control panel |
| Communication | Analog/PWM control interface |
Woodward’s specifications identify the 24 VDC PWM version as suitable for Caterpillar digital controls, with a PWM output of approximately 500 Hz and adjustable droop control.
Woodward 9907-838
Key Features and Benefits — 9907-838
- 24 VDC operating supply
- PWM speed-control output
- Isochronous load sharing
- Droop load-sharing capability
- Integrated PWM output surge protection
- Adjustable load gain
- Adjustable droop
- Suitable for paralleling generator sets
- Compatible with selected Woodward synchronizing and loading accessories
- Designed for industrial generator applications
The surge-protection feature is the practical distinction worth noting when comparing this unit with 9907-175. Both use 24 VDC power and PWM output, but the 9907-838 includes PWM output surge protection.
Related Models
Woodward 9907-175: 24 VDC PWM Load Sharing Module with the same general application but without the PWM output surge-protection feature.
Woodward 9907-252: 24 VDC Load Sharing Module using a 0.5–4.5 VDC analog output rather than PWM.
Woodward 9907-173: Load Sharing Module using a ±3 VDC analog output and 115/230 VAC supply.
Woodward SPM-A: Synchronizer commonly used with compatible generator paralleling and load-sharing systems.
Installation and Maintenance — 9907-838
Before installation, verify the 24 VDC supply, generator CT/PT connections, speed-control input type, PWM wiring, and load-sharing configuration. Shielded signal wiring should be routed according to Woodward’s installation requirements, particularly where electromagnetic interference is present.
After installation, verify generator load measurement and confirm that the load-sharing signal is correctly balanced between parallel generator sets. Check both droop and isochronous operation under controlled loading conditions.
Personally, I would verify the connected speed control before commissioning. The module is specifically intended for systems using a compatible PWM input, so replacing an analog load-sharing module with this version without checking the receiving controller can create an immediate compatibility problem.
Product Warranty — 9907-838
Warranty coverage depends on supplier, equipment condition, and purchase agreement. For new-old-stock, surplus, or refurbished inventory, confirm the exact part number, hardware revision, functional-test results, inspection condition, and warranty period before purchase.
The Woodward 9907-838 should be treated as an exact PWM load-sharing spare. Its 24 VDC supply, Caterpillar-compatible PWM interface, surge protection, and load-sharing configuration should all be verified against the existing generator-control system before installation.
