Woodward 9907-252 Load Sharing Module – 0.5–4.5 Vdc Output for Parallel Generator Sets

Brand WOODWARD

Model Woodward 9907-252

Product Overview

The Woodward 9907-252 is an analog Load Sharing Module (LSM) built by Woodward for generator sets that must run in parallel and share real load proportionally. Documented in Woodward manual 02035, the Woodward 9907-252 senses generator output through three-phase potential transformer (PT) and current transformer (CT) inputs, converts that measurement into a real-power (kW) signal, and compares it with the common load-sharing line shared by the other machines on the bus. The resulting error is applied to the engine speed control as a +0.5 to +4.5 Vdc speed-setting bias, so each prime mover raises or lowers fuel until every unit carries its assigned share of the bus load. Because it works through a standard analog voltage rather than a proprietary digital bus, the Woodward 9907-252 can be applied to engines governed by Woodward controls as well as many third-party electronic governors.

In the automation and power-generation hierarchy, the module occupies the coordination layer between the speed governor and the plant bus: it does not drive the actuator itself, but it continuously re-biases the governor so that paralleled sets neither fight each other nor drift into circulating current and reverse power. The Woodward 9907-252 supports two operating philosophies. In isochronous mode, selected when the droop contact and breaker auxiliary contact are both closed, the module holds constant frequency on an isolated bus while actively balancing kW. In droop mode, taken when either contact opens, the unit follows a selectable 0–11% speed droop so it can run stably against an infinite utility bus or against machines whose governors are not equipped for active load sharing.

Housed in a compact sheet-metal chassis measuring 273.6 × 214.1 × 59.2 mm and weighing roughly 1.4 kg, the module runs from a nominal 24 Vdc supply that may vary between 18 and 32 Vdc without loss of function, which suits battery-backed engine control systems and the voltage sag typical of engine starting. Rated for -40°C to +70°C operation, 95% non-condensing humidity, 4 G vibration and 40 G shock, and listed as industrial control equipment, the Woodward 9907-252 is specified wherever continuous, unattended paralleled generation is required.

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Description

Technical Specifications

Parameter Name	Parameter Value
Product Model	Woodward 9907-252 (Load Sharing Module, 0.5–4.5 Vdc Output)
Manufacturer	Woodward Inc.
Product Type	Analog Generator Load Sharing Module / Speed-Bias Control Module
Power Supply	18–32 Vdc, 24 Vdc nominal, approx. 5 W consumption
Supply Protection	Undervoltage and overvoltage protection to +80 Vdc, reverse-voltage protection to -32 Vdc
3-Phase PT Inputs	95–130 Vac line-to-line nominal; module rated 100–240 Vac, 50–400 Hz
PT Input Burden	1.6 W per phase at 240 Vac; 0.4 W per phase at 120 Vac
3-Phase CT Inputs	3–7 A RMS at full load; 0.1 VA burden per phase
Load Sharing Input	0–3 Vdc into 25 kΩ in isochronous mode
Analog Output	+0.5 Vdc minimum to +4.5 Vdc maximum to engine speed control (terminals 19, 20)
Zero-Error Output	+2.50 ± 0.05 Vdc; output impedance 2 kΩ
Speed Trim	±7.5% with external 10 kΩ, 10-turn potentiometer (terminals 26, 27, 28)
Droop Adjustment	0–11% speed reduction, front-panel adjustable
Synchronizer Input	Compatible with optional Woodward SPM-A synchronizer (terminals 24 positive, 25 negative)
Operating Modes	Isochronous load sharing; droop load control; external 5 Vdc reference option on terminal 21
Operating Temperature	-40°C to +70°C (-40°F to +158°F)
Humidity	Tested at 95% relative humidity, non-condensing
Vibration and Shock	4 G vibration; 40 G shock at 11 ms sawtooth pulse
Dimensions (L × W × H)	273.6 mm × 214.1 mm × 59.2 mm (10.77 × 8.43 × 2.33 in)
Weight	Approximately 1.4 kg (3.08 lb)
Agency Compliance	UL Listed industrial control equipment, CE compliant, CSA certified
Reference Manual	Woodward manual 02035, Load Sharing Module Installation and Operation Manual

Main Features and Advantages

True proportional kW sharing through real power sensing: The Woodward 9907-252 does not infer load from actuator position or fuel rack; it measures it. Three-phase PT voltage and CT current are multiplied inside the module’s power sensor to produce a signal proportional to actual generator kilowatts, and that signal is then compared against the load-sharing line common to all paralleled machines. Because the comparison is made on real power rather than on a proxy, mismatched machine ratings, unequal cable impedances and differing governor gains do not prevent correct sharing, and circulating reactive current does not corrupt the control action.

Isochronous and droop flexibility in one module: A single Woodward 9907-252 covers both operating cases that a paralleling system has to handle. On an isolated bus, closing the droop and breaker auxiliary contacts puts the module into isochronous load sharing, holding frequency constant while it actively equalizes kW. Opening either contact transfers the machine to droop operation at a selected 0–11% setting, which is the correct behavior when the set is tied to a utility bus or run alongside non-compatible governors. Switching between the two requires no reconfiguration software, only a contact, which simplifies both commissioning and operator procedures.

Field-adjustable without software: Droop and Load Gain are set from front-panel potentiometers, and a remote 10 kΩ ten-turn potentiometer on the speed trim input gives operators ±7.5% manual bias for synchronizing by hand or for trimming load demand in droop operation. The Woodward 9907-252 therefore suits plants with no laptop-based tooling: a technician can balance a paralleled bus with a multimeter and a screwdriver. An optional external 5 Vdc reference can be brought in on terminal 21 when the host speed control requires a stabilized reference.

Broad governor compatibility and rugged construction: Because the interface to the prime mover is a simple 0.5–4.5 Vdc speed-setting signal, the Woodward 9907-252 works with Woodward governors and with many non-Woodward electronic speed controls, which makes it a practical retrofit for mixed fleets. The 18–32 Vdc supply tolerance tolerates battery sag during cranking, the -40°C to +70°C range covers arctic skids and engine-room heat, and the 40 G shock and 4 G vibration ratings allow installation in mobile, marine and offshore equipment where lighter controls fail.