Technological advancements driving innovations in servo stabilisers


The looming electricity crunch and fluctuations in voltage have compelled manufacturing units and offices to install stabilisers for their day to day operations. Even a minor fluctuation in voltage can cause equipment to malfunction or break down. A stabiliser controls fluctuations in the input voltage and provides constant output voltage with accuracy. It not only ensures longer life of equipment but also drastically cuts down on the electricity the equipment consumes, leading to a continuous reduction in electricity bills.

By Richa Chakravarty

Wednesday, June 13, 2012: Despite the continuous growth of this market, a major chunk of it is still unorganised with a large number of small scale units manufacturing servo stabilisers and related components like variable transformers, microcontroller based control units, etc. Says Anoop Agarwal, partner, Indo PowerSys Pvt Ltd, “In 2011, the servo stabiliser market witnessed a growth of around 10-12 per cent, and this growth rate will continue in 2012, or maybe even increase by 2-3 per cent.”


Types of stabilisers

A servo stabiliser compares the output voltage with a built-in stable reference voltage source

Haji Kamruddin, managing director, Servokon Systems Ltd
Anoop Agarwal, partner, Indo PowerSys Pvt Ltd

in order to control voltage variations. The control circuit in the stabiliser operates the motor whenever the output voltage falls or rises beyond the pre-set voltage.

The motor is mechanically attached to the arm of a continuously variable auto transformer, which feeds a buck boost transformer. The stabiliser output voltage is compared with the reference voltage and the resultant error signal controls the servo motor, which corrects the voltage by bringing it to the pre-set level.

Different types of servo stabilisers are available in the market which include manual, semi-automatic (logic circuit controls), and fully automatic with microcontroller based control drivers. These servo stabilisers are of two types—air cooled and oil cooled. The most commonly used are the servo stabilisers with DG set MCCB panels, three phase servo stabilisers with or without an ampere meter, single phase servo stabiliser with an auto cut system, and three phase unbalanced servo stabilisers.


Rajendra Singh, managing director, Selvon Instruments (P) Ltd

What players offer

Replacing heavy models, Shakti Industries has introduced a new range of wall mounting servo stabilisers. “Our new range of digital

Ramesh Baid, director, Baid Power Systems Pvt Ltd

servo stabilisers are compact, microcontroller based control drives, light weight, cooled, noiseless, interruption free, with fast operation, specially designed for domestic applications. It comes with high tech protections like high/low voltage protection, short circuit, software embedded system, overload protection, RFI filter and spikes protection, 96 per cent efficiency and with digital display showing real time statistics. Its sleek design is not only hassle free but also fully automatic and maintenance free,” informs Vishesh Bansal, CEO, Shakti Industries. Operating under the brand name Voltech, the company manufactures transformers, servo voltage stabilisers, automatic voltage regulators (AVR) and other power solution product.

Servokon Systems Ltd, a leading manufacturer and exporter of power conditioning products under the brand name Servokon, has taken servo stabilisers league to the next level by introducing unique HT servo stabiliser (HT AVR) and transformers with inbuilt servo stabiliser up to 5000 kVA, where fluctuating voltage is regulated directly on the HT line making it beneficial in many

Automatic and maintenance free stablisers by Selvon Instruments

ways. The company also offers rolling contact digital servo stabilisers, transformers, online UPS (from 10 mVA to 100 kVA), etc. “Our products are standardised with the best quality raw material for better efficiency and latest

Vishesh Bansal, CEO, Shakti Industries

digital microprocessor based circuitry for better accuracy and regulation. With our strict quality checking measures and continuous R&D process, we make sure that our clients always get latest and best products,” says Haji Kamruddin, managing director, Servokon Systems Ltd.

Selvon Instruments offers servo voltage stabilisers up to 2000 kVA and isolation transformers for power line equipment. Based on IGBT technology, the company has developed a software embedded system for stabilisers. “These are more versatile stabilisers, used with three phase/single phase machines/loads. Our stabilisers are designed for minimum time loss with voltage correction at 1000 V/sec. Conforming to relevant IS/BS standards, with exceptionally low output impedance and 98.6 per cent efficiency, our stabilisers are completely maintenance free. Designed through a fault free system, we offer stabilisers keeping the application area of the customer in mind,” says

HT servo stabliser from Servokon Systems Ltd

Rajendra Singh, managing director, Selvon Instruments (P) Ltd.

Power Line Systems, an ISO certified company, manufactures servo voltage stabilisers with IGBT based online UPS systems, variacs, servo motors, CVTs and various industrial and isolation transformers. “Our automatic digital

Voltech servo stablilisers by Shakti Industries

voltage stabilisers range from 5 kVA to 2000 kVA in three phase, while the 1 kVA to 100 kVA models are suitable for single phase. These stabilisers are designed to provide clean, regulated AC power supply in environments with unreliable, fluctuating mains supply,” states Arvind Sharma, senior engineer, Power Line Systems.

Introducing a new concept in servo stabilisers, BPS digital servo controllers offer total solution for control and metering. These controllers are microprocessor based and incorporates circuits for

Servo controlled voltage stabliser from Indo Power Systems

control of servo motors and display of input voltage/output voltage and output current. Fault conditions like over load/over volt/under volt are indicated by respective LEDs.

Among various other advantages, BPS digital servo controllers reduces inventory as no cards/switches/push buttons and spares are required. Same controllers are suitable for wide range of servo stabilisers (from 1 kVA

Microcontroller based programmable digital servo stabiliser from Baid Power Systems

to 500 kVA). This reduces assembly cost as no more fixing of so many components and PCBs and their interconnections are required and no more manual calibration of pre-sets. Informs Ramesh Baid, director, Baid Power Systems Pvt Ltd, “Output voltage/over load/on delay time/trip delay time/hysteresis/over voltage cut out/under voltage cut out are programmable site. The controller has SMPS power supply to support the system from 85 to 280 volts. Thus, the same controller can be used for any input voltage range. To check motor function, the controller can be operated in manual mode. Also, to safeguard from mishandling by unauthorised persons, all programmes are password protected.”

Seven Hills is yet another company that offers digital servo stabilisers with a high correction rate (45 V to 65 V per sec) to meet fluctuations. “These stabilisers have a digital microprocessor controller for quick responses. These stabilisers offer best solution for power solution and also reduces inventory as no cards/switches/push buttons and spares are required,” says Nishant Gupta, owner, Seven Hills.

Indo PowerSys offers an innovative range of static voltage stabilisers, which are economical, compact, reliable and cost effective. “Our IPS SVS range offers a high level of efficiency, and quick response times in a much smaller footprint. This next generation voltage stabiliser is available with isolated/non-isolated output, having been designed for the most demanding industrial/commercial applications,” says Anoop Agarwal.

Technological advancements

Keeping abreast with technological advancements, domestic manufacturers are currently offering servo stabilisers with several innovations. Today, these stabilisers have an exceptionally high speed of voltage correction to meet the demands of modern voltage sensitive equipment. Modern day stabilisers are completely maintenance free, automatic and have an inbuilt auto bypass with no transition time required (In the conventional method, to achieve the auto bypass feature, excessive switch gears are required, which adds to the cost of the system. It also leads to power interruptions during bypass). Today, manufacturers have replaced the legacy logic control cards with microcontroller based control drivers. The whole circuit has been made compact and put inside a microcontroller, which is programmable. The same microcontroller works in any capacity of servo stabiliser. These are also maintenance free.

Pulse width modulation (PWM) controlled IGBT based technology, used in today’s servo stabilisers, offers the advantage of providing auto bypass. This technology makes stabilisers noiseless, interruption-free and helps in fast operation.

The latest static voltage stabilisers have outsmarted conventional servo stabilisers as well as other static tap changing stabilisers. This system uses IGBT as power switches. A direct AC-AC converter circuit improves the overall system response and helps in fast voltage correction. Voltage regulation with the help of buck and boost topology is achieved electronically without any changes in voltage that occur when the system regulates.

Servo motor type automatic voltage regulators (AVR) bring a new technology to the market, which is an electronic device or circuit that maintains an output voltage and makes it consistent to the load current. There are two types of AVRs—relay type and servo motor type. The latter type of AVR uses a magnetic core with a motorised servo mechanism to regulate the voltage. The servo mechanism is the one responsible for switching connections in order to maintain the acceptable voltage. Durability wise, a servo motor type AVR is better than a relay type of AVR, as it can withstand voltage fluctuations better than the solid state relay type, which may easily get damaged.

Some manufacturers are replacing double wound buck boost transformers with tapped auto transformers (TAT), which improves efficiency and saves more energy. Manufacturers claim that the TAT design has an efficiency of up to 99.9 per cent at certain positions against 97-98 per cent efficiency in buck boost transformer based stabilisers.

Tips for buyers

Since the servo stabiliser industry is unorganised, buyers should be very careful while making a purchase decision. The credibility of the company should be looked into, and it is also essential to have some knowledge about the product.

Before selecting a stabiliser, customers need to know how much power they use. By taking an inventory of all the essential electrical loads and doing a basic electrical load evaluation, one can get a good idea about how much power a system needs. One also needs to know about the range of power fluctuations, that is, the maximum and minimum voltage that one gets from the main AC supply.

Customers should also ensure that the servo voltage stabiliser capacity is 20 per cent more than the maximum load. They should ask for the break down voltage (BDV) test report for the transformer oil being filled in the unit. Also, one should insist on having a complete test done as suggested in the standards. Last but not the least, one must make sure that the manufacturer has used branded products, especially AC synchronous servo motors—one of the prime components of the stabiliser.

The price of a servo stabiliser depends on certain major factors at the customer’s end. These are: maximum load capacity (kVA), supply voltage (both the minimum and maximum), and the type of cooling (air/oil cooled). Hence, buyers should know what their requirements are.

Different applications of servo stabilisers

  • Communication devices: Radio transmitters, televisions, cameras, video recorders, radar navigational devices
  • Computers and calculating machines: Personal computers, workstations, servers, peripherals like tape and disc devices, printers, card punches, unit recording machines
  • General laboratory equipment: Spectrometers, photographic processing equipment, chromatographs, etc
  • Electro medical equipment: X-rays, intensive care units, electro cardioscopes, sterilisers, etc
  • General office equipment: Duplicating machines, photocopiers, telex machines, faxes, teleprinters, phototypesetters, general heating, lighting, production and process control equipment

Electronics Bazaar, South Asia’s No.1 Electronics B2B magazine



Please enter your comment!
Please enter your name here

Are you human? *