Stamford · Automatic Voltage Regulators
SX440
SX440 Automatic Voltage Regulator
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In short
The SX440 is a self-excited automatic voltage regulator for Stamford alternators, with single-phase sensing across 190–264 V and selectable 50/60 Hz operation. It adds under-frequency roll-off protection, which reduces excitation if engine speed falls, protecting the machine during heavy block loads.
Fitment
Confirm the frame and winding number against the nameplate before ordering.
| Make | Model / frame | Notes |
|---|---|---|
| Stamford | UCI 224 / UCI 274 | Self-excited builds |
| Stamford | UCD 224 / UCD 274 | — |
| Stamford | HCI 434 | Confirm excitation type |
Specifications
| Sensing | Single-phase, 190–264 V AC |
|---|---|
| Frequency | 50/60 Hz, selectable |
| Excitation | Self-excited |
| Output | 63 V DC continuous at 3.5 A |
| Protection | Under-frequency roll-off |
| Regulation | ±1% |
Cross-references
Equivalent and superseding numbers. Verify against the machine before substituting.
- E000-23412
- SX460
Symptoms that lead here
- Voltage droops badly on motor starting
- Set stalls or trips when large loads are applied
- Unstable output at low engine speed
Questions about this part
What does under-frequency roll-off do?
It reduces excitation proportionally when engine speed drops below a set threshold, so the alternator does not demand more power than the engine can deliver. This prevents the set stalling when a large motor load is applied.