Voltage Regulation & Power Quality
Servo and static voltage stabilizers compared
How servo and static tap-changing voltage stabilizers differ in correction method, speed, accuracy, maintenance and typical duty, with the same criteria for both.
| Criterion | Servo voltage stabilizer | Static tap-changing voltage stabilizer |
|---|---|---|
| Correction method | Servo motor drives a variable transformer feeding a buck-boost transformer | Relays or thyristors switch between transformer taps |
| Typical correction speed | Typically 6–25 V per second; lower on higher ratings | Typically under 1 s per tap step |
| Typical output accuracy | ±1% of set voltage within the input window | ±2–5% of set voltage, by number of taps |
| Wearing parts in the correction path | Brush or roller contact, motor and drive | Relay contacts in relay designs; none with thyristors |
| Rating range offered | Up to 500 kVA; single phase typically up to 25 kVA | Typically 1–100 kVA, single or three phase |
| Suits | Wide or slow drift; larger and more sensitive loads | Dedicated loads and smaller supplies that tolerate a few per cent |
| Routine maintenance | Inspect and replace brush or roller; check motor, drive and cooling | Check switching devices, cooling and indication |
Values are typical and depend on the design and rating; the proposal states the figures for a specific configuration. Neither type removes harmonics, suppresses transients on its own or bridges an interruption.
Tap-changing stabilizers are listed under Voltage Stabilizers & Voltage Controllers, alongside voltage controllers, which set an adjustable output rather than hold a fixed one. The correction method for a given rating is stated in the proposal. Read servo and static voltage stabilizers: where each fits for the background, or share your voltage record for a review.
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