Voltage regulation
Servo Voltage Stabilizers
Servo-driven voltage correction for single-phase and three-phase loads up to 500 kVA.
- Supply
- Single or three phase, 50 Hz
- Output accuracy
- ±1% of set voltage (typical)
- Cooling
- Air or oil cooled
Have a different requirement? Share your application and preferred configuration.
Made for the application.
A servo voltage stabilizer senses its output voltage continuously and drives a variable transformer with a servo motor, which feeds a buck-boost transformer in series with the load. Invitrona manufactures air-cooled and oil-cooled units for single-phase and three-phase supplies up to 500 kVA. The input window, phase control arrangement, protection settings and enclosure are agreed for each requirement from the load schedule and recorded supply conditions.
Typical application contexts
- Commercial buildings and retail sites
- Large residences, villas and farmhouses
- Production machinery and CNC equipment
- Pumping, HVAC and refrigeration plant
- Medical and laboratory equipment rooms
- Multi-site facilities on variable grid supplies
Continuous servo correction
A servo motor moves the variable transformer smoothly, so the output follows the set point without stepping between taps.
Independent phase control
On three-phase units each phase can be corrected on its own, which matters where the supply or the load is unbalanced.
Protection set for the load
Voltage, overload and phase-fault trips are set for the connected equipment and recorded at commissioning.
Bypass for maintenance
A bypass switch keeps the load supplied from the mains while the stabilizer is isolated for inspection.
Air or oil cooling
Air-cooled units suit clean, ventilated rooms; oil-cooled units suit higher ratings, higher ambient temperatures and dusty sites.
Technical specifications
Typical values for the product class. The ratings, options and operating conditions for your equipment are confirmed during engineering review and stated in the quotation.
| Parameter | Value | Condition |
|---|---|---|
| Rating range | Up to 500 kVA | Continuous duty; single-phase units typically up to 25 kVA |
| Input voltage window | 340–480 V AC three phase; 170–270 V AC single phase | Typical wide windows; narrower windows such as 360–450 V AC suit steadier supplies |
| Nominal output | 400 or 415 V AC three phase; 230 V AC single phase | Phase-to-phase and phase-to-neutral respectively; set point agreed for each unit |
| Output accuracy | ±1% of set voltage | Steady state, within the stated input window |
| Correction speed | Typically 6–25 V/s | Lower rates apply to higher ratings; the rate for a unit is stated in the quotation |
| Frequency | 50 Hz | Operation typically within 47–53 Hz |
| Cooling | Air cooled or oil cooled | Oil cooling is usual for higher ratings and hot or dusty rooms |
| Efficiency | Typically 95–98% | At rated load and nominal input |
| Phase control | Independent per phase or balanced (common) control | Independent control for unbalanced supplies or loads |
| Protection | Under-voltage and over-voltage trip; overload and short-circuit trip; single-phasing and phase-reversal trip | Thresholds set at commissioning; fitted devices stated in the quotation |
| Bypass | Manual bypass switch | Automatic bypass by assessment |
| Ambient temperature | 0–45 °C | Derating above 45 °C or above 1,000 m altitude |
| Enclosure and mounting | Powder-coated sheet steel, floor standing; IP21 indoor | Outdoor enclosures such as IP54 by assessment |
| Metering and indication | Digital input and output voltage, output current; status lamps | Communication interfaces by assessment |
Documents & next steps
PDFServo Voltage Stabilizers datasheetTypical specifications · Up to 500 kVADrawings and documents for a specific order are agreed during engineering review.
For a useful first conversation
- Connected and operating load, including motor starting and load behaviour
- Observed incoming-voltage range and site conditions
- Critical equipment, operating priorities and protection expectations
- Installation location, ventilation, access, noise and environmental constraints
- Project responsibilities for supply, installation, commissioning and service
Common questions
A little context before you enquire.
How is a servo voltage stabilizer sized?
Start from the connected load in kVA, add the starting demand of the largest motors and a margin for planned additions, then check the rating at the lowest expected input voltage. An engineer confirms the rating against the load schedule before a quotation is issued.
What input window should I specify?
Specify the window the site actually sees, ideally from voltage recordings over at least a working week. A wider window than needed increases size and cost; a window that is too narrow causes nuisance trips.
Balanced or independent phase control?
Independent control suits sites where the three phase voltages differ from one another or the load is unbalanced. Balanced control suits supplies whose phases rise and fall together.
Air cooled or oil cooled?
Air-cooled units are lighter and suit clean, ventilated indoor rooms. Oil-cooled units are usual for higher ratings, higher ambient temperatures and dusty locations, and need periodic oil checks.
Which standard applies to servo voltage stabilizers?
The Indian standard for servo voltage stabilizers is IS 9815. The standards, inspections and warranty terms that apply to an order are stated in the quotation.
Where it is used
Application pathways that commonly start with this product class.
- Commercial & multi-siteOffices, retail and distributed operations
- Residential & architecturalHomes, buildings and integrated projects
- IndustrialProduction facilities and process equipment
