Woodward 9907-028 Speed & Phase Matching Control

Product Introduction & Engineering Value

When a generator is being paralleled with a live bus, the breaker should not close simply because the generator is at approximately the correct speed. Frequency, phase angle, and the appropriate breaker-close timing all matter. The 9907-028 SPM-A provides the synchronization function required before generator breaker closure and interfaces with compatible Woodward speed/load-control systems.

The key distinction is that 9907-028 does not provide automatic voltage matching. The Woodward 9907-029 is the closely related version that adds 1% voltage matching.

Technical Specifications

These values come primarily from Woodward’s SPM-A manual.

9907-028

9907-028

How 9907-028 Performs Synchronization

The SPM-A compares the generator and bus electrical conditions and generates control signals to bring the generator toward the required synchronization point.

A simplified sequence is:

Generator voltage/frequency → SPM-A comparison → speed-control correction → phase convergence → breaker-close command

The SPM-A can provide speed-trim output to compatible Woodward controls and a breaker-close relay. Woodward specifies:

• High-impedance output for 2301 load-sharing controls
• Low-impedance output for 2301A, EPG, and 2500 load-sharing controls
• EGA/EGM compatibility with the specified external resistor arrangement
• EPG output for EPG controls without load sharing

This means the SPM-A is part of a larger generator control system rather than a standalone governor.

Field Application & Practical Scenario

Generator paralleling with a live bus

A standby generator needs to be connected to an energized plant bus.

The synchronization sequence typically requires:

1. Start the prime mover.
2. Bring generator frequency close to bus frequency.
3. Compare generator and bus phase.
4. Allow the synchronizer to issue speed-trim commands as required.
5. Wait until the phase relationship enters the configured synchronization window.
6. Issue the breaker-close command.
7. Transfer into parallel operation.
8. Allow the load-sharing/control system to establish the required generator loading.

The 9907-028’s ±10° phase-angle specification is particularly important here. The module should not be treated as equivalent to a version configured for a different phase window.

Other application scenarios

Industrial standby generation

• Automatic synchronization before closing a generator breaker
• Utility-bus paralleling

Diesel generator plants

• Multiple-generator synchronization
• Parallel operation with Woodward governor controls

Steam or gas turbine generation

• Synchronization of turbine-driven generators
• Speed-trim interface to compatible Woodward controls

Woodward documents the SPM-A as a synchronizer used with generator systems and compatible Woodward load-sharing controls.

QA & Testing SOP for New Surplus / Refurbished Stock

For a legacy synchronizer, a visual inspection is insufficient. The unit should be tested as a synchronization-control device.

A. Identity verification

Confirm:

• Woodward manufacturer marking
• 9907-028 part number
• Revision, if shown
• Serial number
• Nameplate voltage information

Do not substitute a 9907-029 simply because the housing appears identical.

B. Electrical inspection

Check:

• 115/230 VAC input configuration
• Generator and bus sensing inputs
• Terminal condition
• Internal fuse/protection condition where applicable
• Relay contacts
• Speed-trim output circuitry

C. Functional test

A suitable test procedure should verify:

• 50 Hz operation
• 60 Hz operation
• Generator/bus voltage sensing
• Frequency difference detection
• Phase-angle detection
• Speed-trim output
• Breaker-close relay operation
• RUN/CHECK/PERMISSIVE/OFF modes
• Match-up timing

Woodward specifies internally selectable match-up times of 1/8, 1/4, 1/2, and 1 second, with 1/2 second identified as the factory default in the SPM-A documentation.

D. Documentation

For New Surplus or refurbished stock, record:

• Exact part number
• Revision
• Serial number
• Test date
• Input-voltage test
• Synchronization test result
• Relay test result
• Warranty period

Veteran’s Tech Trap Guide

⚠️ Trap 1 — Confusing 9907-028 with 9907-029

They are closely related SPM-A synchronizers, but the functions differ:

Woodward explicitly identifies these as separate configurations.

PRO TIP: Check the original part number before ordering. Do not select based only on “SPM-A.”

⚠️ Trap 2 — Assuming synchronization means voltage matching

9907-028 performs frequency/phase synchronization but does not provide the automatic 1% voltage-matching function associated with 9907-029.

If the existing generator system depends on automatic voltage matching, the complete AVR/control architecture needs to be checked separately.

⚠️ Trap 3 — Ignoring breaker timing

The SPM-A must account for breaker closing time. Its match-up time is selectable, and the appropriate setting depends on the generator and breaker system.

PRO TIP: Do not change the timing switch simply because a replacement unit arrives with a different setting. Record the original configuration before removal.

⚠️ Trap 4 — Treating the SPM-A as the governor

The 9907-028 does not replace the complete engine/turbine speed-control system.

It works with compatible Woodward controls to provide synchronization-related speed trimming and breaker-close functions. Woodward specifically documents compatibility with 2301A, EPG, 2500 and related control systems.

Dynamic FAQ

What is Woodward 9907-028?

It is a Woodward SPM-A Speed and Phase Matching Synchronizer for generator synchronization. It is designed for 50/60 Hz systems with a ±10° phase-angle matching specification and no automatic voltage matching.

What voltage does the 9907-028 measure?

The SPM-A accepts 115 or 230 VAC RMS generator and bus voltage inputs, with ±10% voltage tolerance.

Does 9907-028 provide voltage matching?

No. The 9907-028 is the no-voltage-matching configuration. Woodward identifies 9907-029 as the corresponding 1% voltage-matching model.

What is the phase-angle setting?

The standard 9907-028 specification is ±10°. Woodward’s SPM-A platform also supports other phase windows depending on the specific part number/configuration.

What is the power consumption?

Woodward specifies 5 W maximum for the SPM-A.

Is 9907-028 still manufactured?

Woodward’s January 2026 Product Change Notification identifies 9907-028 as an alternate SPM-A synchronizer while announcing the obsolescence of 9900-444. The notification lists 9907-028 as the 50/60 Hz, ±10°, no-voltage-matching alternative.

Because lifecycle status can vary by revision and ordering channel, the exact part/serial number should be confirmed with Woodward or an authorized supply channel before treating a particular unit as current production.

What does New Surplus mean for 9907-028?

New Surplus normally means unused inventory that is being sold outside the current factory-production channel. It does not by itself prove factory-new current production. For procurement, request a nameplate photograph, serial number, condition statement, and functional test report.

What warranty should accompany a replacement?

Warranty depends on the supplier and stock condition. The quotation should explicitly identify whether the unit is New Surplus, New in Original Packaging, repaired, or refurbished, and state the applicable warranty period.

Engineering Takeaway

The Woodward 9907-028 is specifically an SPM-A generator synchronizer: 50/60 Hz, ±10° phase matching, 115/230 VAC sensing, and no automatic voltage matching.

For replacement procurement, the most important checks are 9907-028 vs. 9907-029 identification, generator/bus voltage configuration, phase window, breaker match-up time, output compatibility, and the existing Woodward governor architecture. Woodward’s January 2026 documentation also confirms 9907-028 as an active alternate SPM-A configuration in the context of the 9900-444 obsolescence notice.