Automatic Voltage Regulator (AVR)
10kVA – 2000kVA | 1-Phase & 3-Phase | Servo & Static Technology
VoltaPex automatic voltage regulator (AVR) maintains constant output voltage regardless of input fluctuations or load variations. Protects sensitive industrial equipment from voltage sags, surges, and brownouts.
What is an Automatic Voltage Regulator (AVR)?
An automatic voltage regulator (AVR) is a device that maintains a constant output voltage regardless of variations in input voltage or load conditions. In industrial settings, AVRs are critical for protecting sensitive machinery from voltage fluctuation.
Servo Voltage Stabilizer AVR
Uses a servo motor coupled with a variac. Provides high accuracy (±1%), handles heavy inrush currents, and introduces no harmonic distortion. Best for industrial loads with motors.
Static (Relay) AVR
Uses semiconductor switches (thyristors or relays) to select transformer taps. Faster response but lower accuracy (±5-10%) and poor surge handling. Suitable only for resistive loads.
Online / Double-Conversion AVR
Converts AC to DC and back to AC. Provides perfect regulation (±0.5%) and isolation, but lower efficiency (90-94%). Used for data centers and medical imaging.
Digital Voltage Stabilizer
Microcontroller-based AVR with real-time monitoring, data logging, and remote communication capabilities (RS485 Modbus).
Types of Voltage Regulator – Which One Do You Need?
Understanding the different types of voltage regulator is essential for selecting the right equipment for your application.
Servo Voltage Stabilizer (Industrial Grade)
Best for: CNC machines, injection moulding, textile mills, compressors, industrial ovens
Pros: ±1% accuracy, handles motor starting surges, no harmonic distortion, 98%+ efficiency, 200% overload capacity
Cons: Slightly slower than static (50V/sec is still very fast), mechanical parts need periodic maintenance
Static (Relay/Triac) AVR
Best for: Lighting systems, office equipment, small commercial loads (not for heavy machinery)
Pros: Fast response, no moving parts, lower cost
Cons: Lower accuracy (±5-10%), poor surge handling, stepwise correction, can introduce harmonics
Online / Double-Conversion AVR
Best for: Data centers, medical imaging (MRI/CT), semiconductor fab, laboratory equipment
Pros: Perfect isolation, ±0.5% accuracy, zero transfer time, filters all harmonics
Cons: Lower efficiency (90-94%), 2-3x higher cost, cannot handle motor starting surges well
| Input Voltage (Single Phase) | 170V – 270V |
| Input Voltage (3-Phase) | 300V – 490V (Line to Line) |
| Output Voltage | 230V / 415V ±1% (Servo) / ±0.5% (Online) |
| Frequency | 47Hz – 53Hz |
| Correction Speed (Servo) | 50V per second |
| Efficiency (Servo) | ≥98% at full load |
| Efficiency (Online) | 90-94% |
| Response Time (Static) | <1 cycle |
| Overload Capacity (Servo) | 200% for 10 sec |
| Cooling Type | Air / Oil Cooled |
| Standards | IS 9815, IEC 60076, CE |
How Does an Automatic Voltage Regulator Work?
A voltage regulator for industrial use continuously monitors the input voltage through a microprocessor-based controller. When it detects a deviation from the set output, it takes corrective action.
Voltage Sensing
The AVR continuously measures input voltage using potential transformers or resistive dividers.
Error Detection
The controller compares the sensed voltage with the reference voltage (230V or 415V).
Correction Action
For servo AVR: signals servo motor to move variac brush. For static AVR: switches taps electronically.
Output Regulation
Output voltage is maintained within ±1% (servo) or ±0.5% (online) of set value.
The primary function of stabilizer is to protect electrical equipment by providing a constant output voltage despite fluctuating input. Without an AVR, consequences include:
- Undervoltage: Motors draw excessive current, overheat, and fail prematurely
- Overvoltage: Insulation breakdown, capacitor explosions, immediate damage to electronics
- Voltage sags: Contactors drop out, causing production stoppages
How Stabilizer Increase Voltage?
When input voltage is low, the servo motor moves the carbon brush on the variac to a position that adds more turns in series, stepping up the voltage through electromagnetic induction. This happens continuously and automatically.
AVR Stabilizer vs. Servo Stabilizer – What's the Difference?
AVR Stabilizer (Static Type)
An avr stabilizer typically refers to an electronic (static) voltage regulator that uses relays or thyristors to switch transformer taps.
- Fast response (<1 cycle)
- Lower cost for small capacities
- Lower accuracy (±5-10%)
- Cannot handle motor starting surges
Servo Voltage Stabilizer (Recommended)
A servo voltage stabilizer is a specific type of AVR that uses a servo motor and variac – the gold standard for industrial applications.
- High accuracy (±1%)
- Handles 200% overload for motor starting
- No harmonic distortion
- 98%+ efficiency
Popular AVR Stabilizer Capacities
Select the right capacity based on your connected load and application
| kVA Rating | Application | Recommended AVR Type | Input Range | Cooling | Approx. Price (INR) |
|---|---|---|---|---|---|
| 10 kVA | Small workshop / Office | Servo or Static | 170-270V | Air | ₹25,000 – ₹35,000 |
| 15 kVA | CNC lathe / Printing press | Servo (Recommended) | 170-270V | Air | ₹40,000 – ₹55,000 |
| 25 kVA | VMC machine / 3-4 machines | Servo | 300-470V | Air | ₹65,000 – ₹85,000 |
| 30 kVA | Textile section / Small factory | Servo | 290-470V | Air | ₹80,000 – ₹1,00,000 |
| 50 kVA | Small factory mainline | Servo | 280-480V | Air/Oil | ₹1,20,000 – ₹1,50,000 |
| 75 kVA | Plastic moulding plant | Servo (Oil Cooled) | 280-480V | Oil | ₹1,60,000 – ₹2,00,000 |
| 100 kVA | Medium factory mainline | Servo (Oil Cooled) | 270-480V | Oil | ₹1,90,000 – ₹2,40,000 |
| 150 kVA | Large workshop / Textile mill | Servo (Oil Cooled) | 270-480V | Oil | ₹2,50,000 – ₹3,20,000 |
| 200-500 kVA | Cement plant / Steel plant | Servo (Oil Cooled) | 250-480V | Oil | ₹3,50,000 – ₹12,00,000 |
Digital Voltage Stabilizer – Smart Features
Real-time Display
Shows input/output voltage, load current, and load percentage for each phase.
Configurable Settings
Adjustable high/low cut-off points, time delays, and output voltage setpoint.
Data Logging
Records historical voltage data for analysis and predictive maintenance.
Remote Monitoring
RS485 Modbus RTU for integration with SCADA or BMS systems.
Automatic Voltage Regulator (AVR) – Complete Industrial Guide
An automatic voltage regulator (AVR) is an essential component in any industrial facility where voltage fluctuations are common. In India, grid voltage can vary from 180V to 280V in many industrial zones. A quality AVR ensures that your machinery always receives a steady, safe voltage.
What Does a Stabilizer Do? The Function of Stabilizer
The primary function of stabilizer is to protect electrical equipment from voltage fluctuation. Without an AVR, undervoltage causes motors to draw excessive current and overheat, while overvoltage can instantly damage control boards and insulation.
How Stabilizer Increase Voltage – The Mechanism
How stabilizer increase voltage when input is low? In a servo AVR, the microcontroller detects undervoltage and signals the servo motor to move the carbon brush on the variac to a position that adds more turns in series, stepping up the voltage. Conversely, during overvoltage, it steps down. This is the core mechanism of every voltage regulator for industrial use.
Stabilizer Transformer – The Heart of an AVR
The variac inside a servo AVR is often called a stabilizer transformer. It is an autotransformer with a moving brush that picks off the required voltage. VoltaPex uses copper wound stabilizer construction for all our stabilizer transformers. A copper wound stabilizer offers lower electrical resistance, better mechanical strength, and longer service life compared to aluminium.
Stabilizer KVA and Stabilizer Cost
Stabilizer kVA is the capacity rating – sum of all loads to be protected plus 20-30% margin. Stabilizer cost depends on kVA rating, type (servo/static), cooling (air/oil), and features. A 10kVA servo stabilizer costs approximately ₹25,000-35,000, while a 100kVA unit ranges from ₹1.8-2.4 lakh.
High Voltage Stabilizer and Low Voltage Stabilizer – Same Device
A high voltage stabilizer and low voltage stabilizer are the same device – it corrects both undervoltage and overvoltage within its design range. VoltaPex units work from 170V to 270V (single phase) and 300V to 490V (3-phase).
Voltage Regulator for Home vs. Industrial Use
A voltage regulator for home is typically a small static or relay-based unit for protecting TVs, refrigerators, and ACs. For industrial applications, you need a heavy-duty servo voltage stabilizer with 200% overload capacity and copper wound construction.
As a leading industrial stabilizer manufacturer, VoltaPex has supplied thousands of AVRs to industries across India. All our units are copper wound stabilizer with digital controllers and full protection suites.