Woodward 9907-175 PWM Output Load Sharing Module – Rugged –40°C to +70°C Operation

The Woodward 9907-175 is a specialized Load Sharing Module (LSM) designed to provide precise isochronous and droop load-sharing capability for engines equipped with Caterpillar digital speed controls in generator set applications. Acting as the critical interface between Woodward power management accessories and Caterpillar engine governors, the Woodward 9907-175 enables proportional load distribution across multiple paralleled generators, preventing circulating currents and unstable frequency drift when independent power sources operate in tandem.At its core, the Woodward 9907-175 continuously samples three-phase voltage via potential transformers (PTs) and current via current transformers (CTs) to calculate real-time real power (kW) output. It compares this calculated load against a user-defined load gain setpoint and an adjustable droop setting, then generates a corrective signal—specifically a Pulse Width Modulated (PWM) output in the 9907-175 variant—that drives the engine’s digital speed control to increase or decrease fuel delivery. This closed-loop architecture ensures that load is split accurately according to each unit’s rated capacity, whether operating in a constant-frequency isochronous mode or a frequency-varying droop mode.Compatible with Woodward synchronizers such as the SPM-A, paralleling phase switches, import/export controls, and automatic generator loading systems, the Woodward 9907-175 is a field-proven solution for mixed-brand paralleling. Its rugged construction, wide operating temperature range, and built-in voltage protection make it ideally suited for demanding engine-room environments in data centers, hospitals, marine vessels, and industrial emergency power systems.

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Description

Technical Specifications

Parameter Name	Parameter Value
Product Model	9907-175
Manufacturer	Woodward
Product Type	Load Sharing Module (LSM)
Power Supply	18–32 VDC (24 VDC nominal), approx. 5 W
Output Signal	PWM (5 V logic) to Caterpillar digital speed control
PT Inputs	3-phase; 95–130 or 190–260 VAC (jumper selectable), 50–400 Hz
CT Inputs	3-phase; 3–7 A RMS at full load
Load Sharing Input	0–3 VDC (isochronous mode)
Control Modes	Isochronous (0% droop) / Droop (2–6% adjustable)
Synchronizer Compatibility	Woodward SPM-A synchronizer (direct interface)
Input Protection	Undervoltage, overvoltage (>80 VDC), reverse polarity (–32 VDC)
Operating Temperature	–40°C to +70°C
Shock Rating	40 G, 11 ms sawtooth pulse
Enclosure Rating	IP20 (panel mount)
Certifications	CE, UL, cUL
Dimensions (L × W × H)	273.6 × 214.1 × 59.2 mm
Weight (approx.)	1.4 kg

Main Features and Advantages

Precise kW Load Calculation

The Woodward 9907-175 continuously monitors three-phase PT and CT inputs to calculate true real power output. This allows it to distribute load proportionally across paralleled generators with high accuracy, preventing any single unit from hogging the block load while others approach stall conditions.

PWM Output for Caterpillar Integration

Unlike generic load-sharing modules with analog outputs, the Woodward 9907-175 generates a dedicated PWM signal that interfaces directly with Caterpillar digital speed controls. This eliminates the need for external signal converters and allows seamless integration between Woodward power management accessories and Cat engines.

Dual Control Modes

The module supports both isochronous (zero droop) operation for grid-parallel applications requiring constant frequency, and adjustable droop (2–6%) for isolated bus operation where frequency is allowed to vary with load. Mode selection is straightforward via external switches and auxiliary contacts.

Robust Electrical Protection

The Woodward 9907-175 includes comprehensive input protection against undervoltage, overvoltage (up to 80 VDC), and reverse polarity (–32 VDC). This safeguards the module and connected equipment from wiring errors and supply transients commonly encountered during panel rework or maintenance.

Rugged Engine-Room Reliability

With an operating temperature range of –40°C to +70°C and a 40 G shock rating per MIL-STD-810C, the Woodward 9907-175 is engineered to survive the vibration, temperature extremes, and harsh conditions typical of generator enclosures, marine engine rooms, and offshore installations.

Application Field

The Woodward 9907-175 is primarily deployed in applications where two or more generators must operate in parallel and share electrical load proportionally to their rated capacity. In data centers and hospitals, it ensures that emergency backup generator sets synchronize and divide load correctly when utility power fails, preventing frequency instability and potential reverse-power trips that could take generators offline at critical moments.In marine and offshore power management systems, the Woodward 9907-175 balances load between shipboard generators as power demand fluctuates with changing sea states and onboard equipment usage. Its ability to interface Caterpillar digital governors with Woodward synchronizers and load controls makes it particularly valuable for vessels with mixed-brand propulsion or power generation equipment.The module also plays a key role in industrial plants and oil and gas facilities where multiple diesel or gas generator sets must operate in parallel. By maintaining stable load distribution and reducing fuel waste caused by over-fueling on lightly loaded units, the Woodward 9907-175 helps optimize operating efficiency. For legacy installations, it serves as a direct replacement or upgrade path, preserving existing Caterpillar and Woodward infrastructure without requiring a complete control system overhaul.