Woodward SMM40 Speed Adjusting Motor

Woodward SMM40 Speed Adjusting Motor

The Woodward SMM40 Speed Adjusting Motor (Synchronizing Motor) is a bi-directional permanent-magnet actuator engineered specifically for remote speed setting and alternator synchronizing on mechanical-hydraulic governors. Installed directly onto the governor housing, the SMM40 allows switchboard operators or automated power management systems (PMS) to adjust engine rack position, trim generator frequency, and balance active load distribution (kW sharing) in droop or isochronous modes.

Originally manufactured by Sawamura Denki Kogyo expressly for Woodward Governor Company, the SMM40 incorporates an integrated gear reduction unit and an internal friction-type slip clutch calibrated to slip at torque limits (nominal 4.5 lb-in / 0.51 N·m). This protective design prevents motor burnout and gear stripping when reaching maximum/minimum governor speed stops.

Model Details

• Base Model Family: SMM40 (Replaces legacy S40, MM40, and MM4A units)
• Standard Part Numbers (MPN):
  • 1766-523: 24V DC nominal, 0.15 A, 2 RPM rated
  • 1766-531: 220V/240V AC/DC (internal rectifier circuit), 0.15 A
  • 1766-521 / 1766-524 / 1766-528: Multi-range 110V/220V AC variants with internal bridge rectifiers and drop potentiometers
• Motor Classification: Permanent Magnet Synchronizing Motor (Reversible)

Features

1. Drop-In Mechanical Interchangeability: Directly backward-compatible with legacy Woodward S40, MM40, and MM4A speed-setting motors without mounting or drive-coupling alterations.
2. Integral Slip Clutch Overload Protection: Factory-calibrated internal friction clutch protects reduction gear teeth and motor armature during governor physical travel limit contact.
3. Integrated Rectifier & Potentiometer Options: Available with internal rectifier stacks enabling connection across 24V DC, 110V AC, or 220V/240V AC supplies, supplemented by built-in speed-trim potentiometer adjustments.
4. High-Torque Sub-Fractional Actuation: Delivers continuous rated torque up to 0.2 N·m (safe operational torque) at precision low output shaft speeds (0.5 to 9.0 RPM depending on gearhead ratio).
5. Vibration-Damped Construction: Encased in a rugged cast frame with sealed precision bearings, rated to withstand extreme engine-mounted mechanical shock and marine thermal environments.

Technical Specifications

Compatibility

• Woodward UG Series: UG-8 Dial, UG-8 Lever, UG-40 Dial, and UG-40 Lever governors.
• Woodward PSG Series: PSG Hydraulic Governors with motorized speed-setting heads.
• Woodward SG Series: SG mechanical-hydraulic governors configured for alternator frequency control.
• Prime Mover Integrations: Marine diesel generator sets (MAN B&W, Wärtsilä, Daihatsu, Yanmar, Bergen, Caterpillar, Cummins), steam turbine generator governors, and marine main propulsion drives running droop/isochronous modes.

Part Number Cross-References

• Direct Successor To: Woodward S40, Woodward MM40, Woodward MM4A
• OEM Assembly Cross-References:
• Woodward: 1766-523, 1766-524, 1766-525, 1766-531, 1766-532, 1766-561
• Sawamura Denki Kogyo: SMM40-XX series
• Woodward Manual Reference: Manual 03026 (Permanent Magnetic Field Synchronizing Motors)

Applications

• Remote frequency synchronization and automated paralleling of marine diesel generating sets.
• Proportional switchboard load-sharing adjustment on alternator sets operating in droop mode.
• Remote engine setpoint adjustment for marine main propulsion diesel engines with UG-8 or UG-40 hydraulic governors.
• Industrial co-generation turbine speed trim in power plants, pulp mills, and chemical refineries.
• Retrofit projects replacing mechanical manual synchronizing linkages with centralized digital Power Management System (PMS) relay outputs.

Frequently Asked Questions

Can the Woodward SMM40 replace legacy S40 and MM40 synchronizing motors directly?

Yes. The SMM40 is engineered with matching mounting dimensions, drive gear alignment, and shaft centerlines to serve as a direct drop-in replacement for Woodward S40, MM40, and MM4A motors without requiring modifications to the governor top cover or mechanical linkage.

What is the exact function of the internal slip-clutch on the SMM40?

The mechanical friction slip-clutch decouples the motor drive when the governor’s internal speed-setting mechanism hits its upper or lower mechanical limits. It prevents gear stripping, shaft shearing, and motor burnouts while allowing manual overrides via the governor knob.

How do I configure the SMM40 for 24 VDC vs. 220 VAC systems?

The Woodward SMM40 is supplied in dedicated factory configurations. Standard 24 VDC units operate directly via DC control loops, while 110/220/240 VAC variants feature internal solid-state rectifiers and an integrated terminal distribution board with a dedicated Common terminal (Terminal C).

What torque should the friction slip-clutch be adjusted to?

The slip-clutch must be calibrated to approximately 4.5 lb-in (0.51 N·m). This provides sufficient holding force to actuate the governor speeder spring while slipping safely under stall conditions.

Why is alternator synchronization sluggish when using the SMM40?

Sluggish synchronization is typically caused by three issues: a loosened slip-clutch slipping under speeder spring load, low supply voltage at the motor terminals during actuation, or the internal trimming potentiometer being dialed too close to the “Slow” (S) limit.