Stabilizers

INTRODUCTION

Fluctuating supply voltage is a menace to electrical equipment. The magnitude of a supply voltage should be reasonably constant to ensure life expectancy of the connected equipment and optimum output. Unfortunately, the supply systems due to the various constraints faced by them are subjected to wide fluctuations.
Various types of stabilizers are manufactured for different industries to combat the menace of supply voltage fluctuations. Undoubtedly the most popular among these are the stabilizers which work on the principle of servo control. They are designed to meet the requirements of a majority of voltage control problems.
DONVEY manufacture Type AVR-14 Automatic voltage stabilizers employing servo control principle with unique features.

LIMITATIONS

The application of AVR – 14’s are limited only in cases where an instantaneous correction is a must. The stabilizing action needs a few seconds to cover the entire range.

OPERATING PRINCIPLE

In AVR – 14 the output voltage is monitored and sensed continuously by a control circuitry (7). This circuitry controls the movement of a low speed high torque bi-directional stepper-synchronous motor (3,4,5 & 6) operating to step-down or step up the input voltage as per requirement (to maintain to fairly constant output voltage) by using a series buck /boost transformer (2) and a continuously variable voltage auto transformer (1) combination.

EXCLUSIVE FEATURES

Servo controlled voltage stabilizers are extremely popular for their many outstanding features. DONVEY make stabilizers have some additional features which are very useful to the user. Some of them are mentioned below:

• faster rate of correction upto 105V per second.
• Quick response time of 10 m /sec.
• isolated servo drive without relays. Hence no noise generation.
• no wave form distortion is introduced by the stabilizer. The output wave form is a virtual replica of input wave form
  
• low internal impedance.
• negligible phase shift ensuring no change in system power factor.
• the stabilization characteristic is independent of load magnitude.
• the employment of state of art I.C. Technology and solid state control with temperature compensation.
• extremely high efficiency by use of prime CRGO and electrolytic copper of 99.9% purity.
• Conforming to stringent defence standard specification JSS 55555 and IS : 9815 (latest).
• Alarm Annuctiation by LED.
• tailor made to suit customers requirements.
• stringent quality control of raw material and quality check of subassemblies at every stage of manufacture.

OPTIONAL FEATURES

DONVEY offers a wide range of useful features as per customer’s request. They may be for special indications, protective controls, special metering etc. the list below is just to give an ideal of the features offered and is not exhaustive.

A) Special meters

• Ammeter to indicate load current with ph Selector switch for 3 ph units.
• Frequency meter
• Digital meters.

B) Monitoring of faults

Visual and / or audible indication can be had if :

• The output voltage is above or below a specified load.
• Load current exceeds safe limit. This alarm remains even when there is tripping provision.
• One or more phases in a 3 phase input has failed.
• Frequency of supply is not within permissible range.
• Audible alarm acknowledgment facility.
  

C) Tripping on faults

Protection: Suitable contractors may be provided on output side and / or input side, to trip off the supply to the equipment connected to the stabilizer when any of the above fault occurs. Normally a time-delay is provided to avoid nuisance tripping when the fault is of temporary nature.

D) Remote control facility

On special request the stabilizer may be provided with remote control panels. This feature is particularly suitable for use where due to some constraints the voluminous power handling sections are not easy to install.

A SPECIAL OPTION: TYPE AVR – 14 D

In case the customer so desires, DONVEY can supply. Type AVR – 14 A.C. Voltage stabilizers with D.C. motor in place of stepper synchronous motor shown in Figure.

FOR CNC CUSTOMERS DONVEY OFFERS PROVEN DESIGN OF SERVO VOLTAGE STABILIZER AND SERVO TRANSFORMER IN SINGLE CABINET. MAXIMUM CAPACITY : 35KVA.

STANDARD FEATURES

• Voltmeters to indicate both input and output voltages. In case of 3 ph. Unit, provision is made for measuring ph to ph to neutral voltages.
• Facility for auto manual operation. This features enables the users to control the output voltage manually as and when required. This feature is extremely useful at site for checking the automatic operation of the stabilizer.
• Indicating lamp to show that the input voltage is beyond the range of correction for the unit.
• Output voltage may be set within a range of about 20 volts (line to neutral) under proportionate loading conditions and input voltage range shift.
• The output voltage accuracy is set for a stability within + 1% of the nominal value.
• Easily replaceable plug-in control card ensures fast replacement.
• Control card is printed on a glass epoxy board with workmanship of highest degree. Gold plated contacts ensure faultless contact and long life.
• Replacement of the card is easy.

Technical Specification

• Air Cooled Stabilizer
  

  1	Nominal Output voltage	415 Internally settable at 380v to 400v
  2	Input regulation range	310v - 480v or 340v - 480v
  3	Output voltage regulation	1% of nominal voltage
  4	Input frequency range	47Hz - 53Hz
  5	Avrage correction rate	48v/sec(L_L)
  6	Servo motor drive	A.C synchronous stepper motor
  7	Short circuit protection	HRC fuse at input
  8	Single phasing prevention	Individual phase voltage sensing method
  9	Efficiency	Greater than 97%
  10	Electronic cut off Output high cut off Output low cut off Output overload cutoff	+5% above nominal output voltage -10% below nominal output voltage 110% rated current
  11	Annunciation panel LED indication	Input present, output normal, output high, output low and overload.
  12	Overload resetting mode	Manual / automatic after time delay at 2 -3 minutes.
  13	Stabilizer bypass	Manual change over switch
  14	Output voltage indication	Digital voltmeter with selector switch to read RY, YB, BR voltage

  
  

• Oil Cooled Stabilizer
  

  1	Nominal Output voltage	415 Internally settable at 380v to 400v
  2	Input regulation range	360v - 460v or 340v - 480v or 310v - 480v
  3	Output voltage regulation	1% of nominal voltage
  4	Input frequency range	47Hz - 53Hz
  5	Average correction rate	48v/sec(L_L)
  6	Servo motor drive	A.C synchronous stepper motor
  7	Short circuit protection	HRC fuse at input
  8	Single phasing prevention	Individual phase voltage sensing method
  9	Efficiency	Greater than 97%
  10	Electronic cut off Output high cut off Output low cut off Output overload cutoff	+5% above nominal output voltage -10% below nominal output voltage 110% rated current
  11	Annunciation panel LED indication	Input present, output normal, output high, output low and overload.
  12	Resetting indication	Visual for overload
  13	Overload resetting mode	Manual / automatic after time delay at 2 -3 minutes.
  14	Stabilizer bypass	Manual change over switch upto 50KVA
  15	Output voltage indiaction	Digital voltmeter with selector switch to read RY, YB, BR voltage

Field of Application

• Autoconers, textile machines, Knitting machines.
• Information Technology and call centers.
• Computer and Microprocessor Controlled Equipment.
• Sophisticated research instruments used in Scientific, Medical, Agriculture, Educational, And other Research Institutions.
• Offset Printing Presses. Color Scanners, Processors, Phototypesetters, Photographic Equipment, Photo Copiers and Packaging Industries.
• Medical Equipment, X-ray machines, E.C.G Machines/Monitors. MRI, CT Scan etc.
• Defense Installations, LPTs, HPTs, Broadcasting and Telecommunication.
• Lifts, Escalator and Elevators.
• Central, Air-conditioning Plants, Processing Plants, Chemical Industries, Textile Industries.
• CNC Machines, Laser Machines and Moulding Machines etc.
• Commercial Buildings and Complexes.
• Complete Hospitals and Nursing Homes.