Servo Voltage Stabilizer

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Overview

Servo Voltage Stabilizer

SERVOLINK is an ISO 9001:2015 certified organization and a registered MSME, NSIC and D&B unit engaged in manufacturing, exports and marketing of all types of Servo Voltage Stabilizers, Variable Auto Transformers, Constant Voltage Transformers and Isolation Transformers.

Our products are specially manufactured using precise engineering in order to offer accurate performance and low power losses. We use premium-grade raw materials along with advanced technology while manufacturing our products to ensure high operational performance.

We have over 4 decades of experience in the domestic and government sectors, and have also gained international exposure and reputation over the years. We are recognized in countries like the UAE, Afghanistan, Saudi Arabia, Bangladesh, Nepal and Libya.

Servolink servo voltage stabilizer range — single phase, three phase, air cooled and oil cooled models

The Basics

What Is A Servo Voltage Stabilizer?

A servo voltage stabilizer is a piece of electrical equipment which protects your machines, electronic appliances and sensitive equipment from voltage ups and downs. It is manufactured as per IS 9815 (Part 1):1994 (Reaffirmed 2004), titled Servo-Motor Operated Automatic Line Voltage Correctors. It is placed between your power supply and your appliances, so it constantly monitors the incoming voltage. Whenever the voltage moves too high or too low, it corrects it instantly, so your equipment always receives a steady, safe supply.

Why does this matter? Unstable voltage rarely damages equipment all at once. It causes slow, hidden wear and tear. Motors heat up, compressors work harder than they should, and electronic parts age faster than expected. Over time, this leads to machinery breakdowns, repair bills and frustrating interruptions. A servo stabilizer helps you avoid all of that and get the full life out of your equipment.

A servo voltage stabilizer is also known as a servo stabilizer, voltage stabilizer, voltage regulator, or Servo Controlled Voltage Stabilizer (SCVS). Depending on the supply and cooling type, it is also called a single-phase stabilizer, three-phase stabilizer, air-cooled servo stabilizer, or oil-cooled servo stabilizer. All these names refer to the same product and the same purpose: keeping your power supply steady and your equipment safe.

The Four Models

Types Of Servo Voltage Stabilizers

Servo voltage stabilizers come in four main types. Choosing the right one depends on two simple things: whether your property uses single-phase or three-phase power, and whether the unit needs air or oil cooling based on how hard it will work.

Single-Phase Air-Cooled (3 to 50 kVA)

The ideal choice for most homes, small offices, clinics and shops. It works with a standard single-phase supply and stays cool using natural airflow or a built-in fan. Compact, easy to install and needs very little maintenance — perfect for protecting ACs, refrigerators, computers and other everyday appliances.

View product → 02

Single-Phase Oil-Cooled (10 to 50 kVA)

If your equipment runs for long hours, or your location is hot, dusty or has poor power supply, this model is a smart pick. Its transformer is kept in oil, which handles heat much better than air, so it keeps working reliably even under tough conditions — a great fit for workshops, labs and rural areas.

View product → 03

Three-Phase Air-Cooled (6 to 100 kVA)

Made for businesses that run on three-phase power, this model keeps all three supply lines stable while using fans for cooling. Well suited to offices, hotels, showrooms and small factories, especially when installed in a clean, airy space.

View product → 04

Three-Phase Oil-Cooled (25 to 2000 kVA)

The choice for heavy-duty, non-stop operations. Large factories, hospitals, data centers and CNC workshops rely on it because it handles big loads around the clock, even in heat, humidity or dust. It costs a little more upfront, but its strength and long service life make it a wise investment.

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What You Gain

Benefits Of A Servo Voltage Stabilizer

Longer Life For Your Equipment

Steady voltage reduces the stress on motors, compressors and electronic parts. Your appliances and machines run the way they were designed to and last much longer.

Highly Accurate Output

A servo stabilizer keeps voltage within about ±1% of the set level. This precision makes it a trusted choice for sensitive equipment like medical devices, CNC machines and laboratory instruments.

Fewer Breakdowns And Repair Costs

By stopping voltage damage before it starts, a servo stabilizer helps you avoid sudden failures, expensive repairs and early replacements.

No Unexpected Shutdowns

Machines that trip or stop midway can disrupt work and waste materials. With a stable supply, your operations run smoothly without interruption.

Better Performance

Equipment running on the correct voltage works at its best. Motors don’t overheat, ACs cool properly, and less energy goes to waste.

Handles A Wide Range Of Fluctuations

Whether the voltage drops sharply in the evening or rises late at night, the stabilizer corrects it smoothly, even in areas with poor or unpredictable supply.

Built-In Safety Protection

Servolink stabilizers cut off the output during extreme high or low voltage, giving your equipment an extra layer of protection. Overload and short-circuit protection are available as per model.

Smooth, Step-Free Correction

Unlike stabilizers that switch in sudden steps, a servo stabilizer adjusts voltage gradually. There are no sudden jumps or flickers, just consistent, clean power.

Step By Step

How Does A Servo Voltage Stabilizer Work?

A servo voltage stabilizer works through a smart combination of electronic control and mechanical movement. Here is what happens inside, step by step.

Power Enters The StabilizerThe supply from the mains first enters the servo stabilizer as input voltage. This same input also feeds the variac and the buck-boost transformer inside, whose job is to buck (reduce) or boost (increase) the voltage according to the required parameters.

The Control Card Senses The VoltageThe servo control card continuously senses the incoming voltage. Three key parameters are set on this card — the input low cut value (lowest input it will accept), the input high cut value (highest input it will accept), and the set output voltage it delivers to your equipment.

Checking The Voltage RangeWhen the input voltage falls within the set range, the control card accepts it and keeps monitoring it closely. If the voltage moves outside the low or high cut limits, the stabilizer protects your equipment by cutting off the output through the output contactor/relay.

Signal To The MotorWhenever the voltage drifts even a few volts above or below the set output voltage, the control card sends a signal to an AC synchronous motor. On low voltage the motor moves forward; on high voltage it moves in reverse.

Gears Move The VariacThe motor’s gears are connected to the gear fittings of the variac shaft (brush arm). As the motor turns forward or in reverse, it moves the brush arm in the same direction, exactly as per the set parameters.

Carbon Brushes Make The CorrectionAttached to the brush arm are fingers that hold carbon brushes. These glide along the variac’s copper-wound track, changing the voltage feeding the buck-boost transformer, which then raises or lowers the supply as needed. When the brush crosses the tapping point of the variac, the polarity of the buck-boost transformer reverses — this is how boost changes into buck.

Stable Output DeliveredOnce corrected, the stabilized voltage flows out through the output terminals to your connected equipment. The control card keeps watching the supply, ready to repeat the correction the moment the voltage changes again.

In simple terms: voltage drops, the motor moves forward and boosts it. Voltage rises, the motor reverses and reduces it. Your equipment always receives steady, reliable power.

Technical Diagram

Working Mechanism

The diagrams below show how a servo voltage stabilizer corrects your power supply. The solid coloured lines show the flow of electricity, and the dashed lines show the control system that keeps watch over it. Follow the numbers to see each step, from the incoming supply to stable power at the output terminals.

Single-Phase Servo Voltage Stabilizer

Tap the diagram to open it full size

Mains inputSupply enters at L and N and passes through the MCB.
SensingThe control card reads the input and output voltage.
Range checkIf voltage goes beyond the low or high cut, the contactor cuts off the output.
Motor driveIf the output drifts, the card runs the servo motor forward or in reverse.
Brush movesThe motor turns the carbon brush along the variac’s copper track.
Buck or boostThe variac feeds the BBT primary and input. The secondary-output winding adds or subtracts that voltage in series.
Stable outputCorrected voltage passes through the contactor to output terminal O.

Three-Phase Servo Voltage Stabilizer

Tap the diagram to open it full size

Mains inputR, Y, B supply enters through the 3-pole MCB.
SensingThe control card reads the input and output of every phase.
Range checkIf any phase goes beyond the low or high cut, the contactor cuts off the output.
Motor driveThe card runs that phase’s servo motor forward or in reverse.
Brush movesThe motor turns the carbon brush on that phase’s variac.
Buck or boostThe variac feeds the BBT primary and input. The secondary-output winding adds or subtracts voltage in series.
Stable outputCorrected R, Y, B voltage passes through the contactor to the output terminals.

Where They're Used

Applications

IT & Call Centers: Information Technology and call centers.

Computer & Micro-Processor Equipment: Computer and Micro-Processor Controlled Equipments.

Research Institutions: Sophisticated research instruments used in Scientific, Medical, Agricultural, Educational, and other Research Institutions.

Printing & Packaging: Offset Printing Presses, Color Scanners, Processors, Phototypesetters, Photographic Equipments, Photocopies, and Packaging Industries.

Medical Equipment: Medical Equipment, X-Ray Machines, E.C.G Machines / Monitors, MRI, CT Scans, etc.

Defence & Telecom: Defence Installations, LPTs, HPTs, Broadcasting & Telecommunications.

Lifts & Elevators: Lifts, Escalators, and Elevators.

Industrial Plants: Central Air-Conditioning Plants Processing plants, Chemical Industrial, Textile Industries.

CNC & Laser Machines: CNC Machines, Laser Machines and Moulding Machines, etc.

Commercial Buildings: Commercial Buildings and Complexes.

Hospitals & Nursing Homes: Complete Hospital and Nursing Homes.

Technical Data

Technical Data Sheet

Make	SERVOLINK
Capacity	3 – 2000 kVA
Input Voltage Range (Three Phase)	240–470 V, 300–470 V, 340–470 V; custom down to 100 V per phase
Input Voltage Range (Single Phase)	100–270 V, 140–270 V, 170–270 V, 180–270 V
Output Voltage	415 V ±1% (three phase) · 230 V ±1% (single phase); 380 / 400 V on request
System	Three phase: unbalanced type, 4 wire, each phase corrected separately · Single phase: phase + neutral
Type	Three Phase · Single Phase
Installation	Indoor; oil cooled also outdoor under shed
Standard	Conforms to IS 9815 (Part 1):1994, IS 5142, IS 302 (Part 1)
Frequency	50 Hz
Wave Form Distortion	Nil
Effect of Load Power Factor	Nil
Response Time	Less than 100 ms
Speed of Correction	20 to 60 V/sec
Mode of Operation	Automatic
Suitability	Suitable for all power factors
Duty Cycle	Continuous 24 hrs
Efficiency	More than 98%
Losses at No Load	0.12% of the total capacity
Losses at Full Load	0.7%
Insulation	Class-H
Cooling	Air Cooled / Oil Cooled
Ambient Operating Temperature	Up to 50°C
Laminations Used	Imported low loss CRGO laminations, M4 grade
Output Cut-off	High/low cut-off through contactor
Mounting	Wheels on higher ratings; base channel on smaller ratings
Display	LCD display panel
Panel Indications	R/Y/B phase input voltage and output voltage
Alarm	High/low input and output voltage
Standard Protections	High/low cut-off · Single phase preventer and phase reversal (three phase) · Restart time delay
Optional Protections	Overload and short circuit · Earth fault · Manual bypass

Made In-House

Why Servolink?

Servolink offers a complete range of servo voltage stabilizers, and we manufacture this equipment in line with the standards set by the Bureau of Indian Standards (BIS):

IS 9815 (Part 1):1994Servo-motor operated automatic line voltage correctors.

IS 5142Continuously variable voltage auto-transformer — the core of the servo mechanism that mechanically regulates the stabilization of electrical supply.

IS 302 (Part 1)General safety requirements for household and similar electrical appliances. For our single-phase domestic models we ensure safety checks such as insulation resistance and earthing provisions.

We follow all these standard checks at the Servolink manufacturing unit, with proper infrastructure from testing labs to individual work stations for every process. In India, we are one of the very few manufacturers with complete in-house manufacturing, which covers:

CRGO core coil winding
Copper wire winding
Fabrication of tanks
Motorization of the variac
Buck-boost winding station
Servo stabilizer assembly points
Testing lab with all test equipment, to perform every test as per Indian Standards before dispatch

This applies to both single-phase and three-phase servo stabilizer units, in air-cooled and oil-cooled models, built to suit every load and area.

Not sure which model you need? Our team will help you choose the right type and capacity based on your equipment, power supply and working conditions. We also provide professional installation and dependable after-sales support.

Questions

Frequently Asked Questions

What is the difference between a servo stabilizer and a relay stabilizer?

A relay stabilizer uses relays to switch between transformer taps, so it corrects voltage in steps and its accuracy is lower. A servo stabilizer uses a motor-driven variac, so it corrects voltage smoothly without steps and keeps the output within about ±1%. Relay stabilizers suit small home appliances, while servo stabilizers are the right choice for sensitive equipment, machines and heavy loads.

How do I choose the right kVA capacity?

Add up the load of all the equipment that will run together, and take extra care with motors, compressors and lifts, because they draw a high current when they start. Then choose a rating so that this running load stays around 60–70% of the stabilizer rating, so the stabilizer never runs at full load all the time. You can use our kVA calculator, or share your load details with our team and we will suggest the right capacity.

Should I choose an air-cooled or an oil-cooled servo stabilizer?

Air-cooled models are suitable for homes, offices and shops with moderate loads and clean, airy installation spaces. Oil-cooled models are better for long running hours, heavy loads, and hot, dusty or humid locations, because oil handles heat much better than air. In three phase, loads above 100 kVA should go for oil cooled.

Do I need a single-phase or a three-phase servo stabilizer?

It depends on your power supply and your equipment. If your property has a single-phase supply, you need a single-phase stabilizer. If you have a three-phase supply or three-phase machines such as lifts, CNC machines or industrial motors, you need a three-phase stabilizer.

Can a servo stabilizer be used for a lift or elevator?

Yes. Lifts run on three-phase motors that are sensitive to low voltage and draw a high starting current, so a three-phase servo stabilizer with the right capacity protects the lift motor and controller and reduces breakdowns.

Does a servo stabilizer need maintenance?

Yes, but very little. The carbon brushes should be checked periodically and replaced when worn, dust should be cleaned, and connections should be kept tight. In oil-cooled models, the oil level and oil condition should also be checked from time to time.

Does a servo stabilizer save electricity?

A servo stabilizer is not a power-saving device. It protects your equipment by giving it the correct voltage, so motors don’t overheat and appliances work at their best, which avoids the energy that is wasted when equipment runs on wrong voltage.

What happens if the voltage goes too high or too low?

Every stabilizer has a set input low cut and high cut value. If the incoming voltage goes outside this range, the stabilizer cuts off the output to protect your equipment, and restores the supply after a time delay once the voltage returns to the safe range.

Credentials