Description of POWER Make Automatic Voltage Controller (Range: 30 KVA TO 8000 KVA)

Power make Servo Stabilizer / Servo Voltage Controller primarily consists of the following

1. Linear, Plus / Minus Type Vertical Rolling Contact Voltage Regulator
In our voltage regulator we are using heavy section of electrolytic grade rectangular copper strip instead of copper wire to minimize the losses & increase the efficiency of equipment. We are also using self lubricating carbon roller assemblies instead of ordinary carbon brushes which offer more reliability and trouble free performance of the equipment.

2. Double Wound Buck / Boost Type Series Transformer
In our Buck / Boost transformer we are using CRGO lamination to minimize iron losses. Coils of Buck / Boost transformer are wound with heavy section of multi strips electrolytic copper to minimize copper losses for getting better efficiency of the equipment.

3. Electronic Control Circuit and Meter Panel
Automatic Servo Voltage Controller consists of very simple electronic control voltage circuit for monitoring and controlling voltage, repair & maintenance of which is very easy. The regulator and Buck / Boost transformer are oil cooled, housed in same or separate sheet steel tanks. Radiators are provided for effective cooling. The coils of voltage regulator & Buck / Boost Transformers are vacuum impregnated and oven dried as per IS.

Inner View of Stabilizer
(Balanced Type)

Effect of Unbalanced Input Voltage between Phase to Phase:
Industrial units situated in residential / commercial areas and not having their own distribution transformer, have the problem of unbalance input voltage between phase to phase and many have the problem of frequent failure of three phase motors. Normally unbalanced input voltage problem persists for few hours a day and will have the following effects on the three phase motors:

1.With 5% Unbalanced Input Voltage between phase to phase – the LOAD will be unbalanced and the capacity of the motor reduces by 40%.
2.Consumption of the three phase motor will increase by 20 – 25%.

To avoid frequent tripping of the overload relays and to continue production, setting of motor relay is kept higher than actual required. The motor (particularly smaller motors upto 7.5 H.P.) cannot withstand this high current for long time and in most cases the motor burns out and this high current flows through the relays, contactors, cables etc. resulting in failure of the same and in some of the cases may cause fire also.The best option for such Units having Unbalanced input voltage, is to install servo voltage stabilizers and servo voltage controller with individual phase control.

Inner view of 3500 KVA AVC


Inner view Automatic Voltage Controller
(Unbalanced type) Export

Close view of Regulator & Carbon Roller Asembly

Basic Circut

Types of POWER Make Servo Voltage Stabilizer

Automatic Voltage Controller (Balance Type) with Special Export Control Circuit

Automatic Voltage Controller
(Balance Type) Standard Type

Automatic Voltage Controller
(Unbalance Type) Standard Type

Automatic Voltage Controller
(Unbalance Type) with Special Export
Control Circuit

Automatic Voltage Controller
(Unbalanced Type)
With special Control Circuit + Phase Shifter +
Complete Bypass Arrangement

Automatic Voltage Controller
(Balanced Type) With special Control Circuit
+ Complete Bypass Arrangement

1000 Automatic Voltage Controller AVC
(Unbalanced Type Complete Bypass Arrangement)

750 KVA Automatic Voltage Controller
(Balanced Type With special Controller Moudules)

500 KVA Automatic Voltage Controller
(Unbalanced type with special control Moudules)

150 KVA Automatic Voltage Controller
(Unbalanced complete Bypass Arrangement)

50 KVA Automatic Voltage Controller
(Unbalance Type) Special Control Modules
+ Bye Pass + Tripping with Protection Circuit

40 KVA Automatic Voltage Controller
(Unbalanced Type + Complete
ByePass Arrangement) Standard Type


Servo Stabilizer are available in wide range and various models.The standard three phase are suitable for balanced & unbalanced supply and loads.The standard models confirm to the following specification:

Input Voltage 360-450 V 350-460 V 340-460 V 340-480 V 320-480 V 300-500 V
Efficiency (as per calculation) 99.5% 99.3% 99.10% 99% 98.7% 98.10%
Output Voltage 400 V±1%,3Phase,50 Hz STANDARD ACCESSORIES
Output Voltage Adjustent ±5% 1. Voltmeter with Selector Switch for I/P & O/P
Output Voltage Regulation ±1% (at no load / full load) 2. Ammeter with Selector Switch
Corection Rate 10V -15V/second(or as per requirment) 3. MCBs for control circuit
Temperature Rise(Max) 35° C- 40° C above ambient 4. Lifting Lugs
Cooling Naturally Oil Cooled 5. Drain Valve
Insulation Class ‘A’ 6. Oil Lever Gauge
Type Indoor 7. Earthing Terminal
Mode of System Fully Automatic/Semi Automatic/Mannual 8. Rating Plate
Mounting On Uni-directional Wheel 9. Junction Box
Wave form distortion Nil 10. Thermometer Pocket
Duty Cycle 100% Continuous

* All specification / calculations are subjected to change due to regular improvement in products without prior notice

  • Reduction in Breakdown of Electrical Equipments
  • Improvement in power Factor (only in case of High Voltage)
  • Power Saving (reduction in Power Bills)
  • Depreciation as per Income Tax Act. in India
  • Uniform Quality of end Products
  • Better Efficiency in Plant
  • Reduction in MDI

Features of Automatic Voltage Stabilizer

The efficiency of power make stabilizers is more than 98-99% in comparison to 93-97% of conventional make available in the market depending upon the input voltage range. Thus, a 500 KVA conventional type stabilizer or conventional servo voltage stabilizers will consume additional power itself minimum Rs. 80,000 p.a. (even when running at 60% load and 20 hours a day) on account of its lower efficiency by 2%

The life of make servo voltage stabilizers is more than 10/15 years at full load in comparison to 2/3 years of conventional make.

Conventional type stabilizers are suitable for 30-40% load on continuous duty cycle. Our automatic voltage stabilizers are Heavy Duty & Industrial type and are suitable for 100% load continuous duty cycle. For running load of 200 KVA, generally 400 KVA / 500 KVA conventional type stabilizer is installed while make 200 / 250 KVA is suitable.

Our automatic voltage stabilizers are guaranteed unconditionally for 5 years in INDIA as compared to 1 year of conventional make.

Owing to its high efficiency and associated benefits, the payback period for the cost of POWER’S Servo Voltage Stabilizers is from 6-12 months depending upon the input voltage variation and number of working hours of the plant. The HIGHER the input voltage the SHORTER will be the payback period.

We have all India servicing network to provide immediate service to our customers. The Service Engineers also visit monthly in their respective areas for routine check-ups. Also, servo controlled voltage stabilizers are categorized under ENERGY SAVING. The servo controlled voltage stabilizers should be such that its own consumption is minimum otherwise the basic concept of Energy conservation will be lost. Therefore while deciding for a stabilizer it becomes necessary to invest the capital over a period of time to ensure that its running cost is minimum and payback period is quickest. From the above facts, you will find that our automatic voltage stabilizers will cost much lesser in long run to conventional type stabilizers.

Automatic Voltage Controllers and Automatic Servo Voltage Controllers are designed for max. 35-40 degree temperature rise at top of oil whereas allowed limit is 50° C.

Inner View of Automatic Voltage
Controller Unbalanced Type with
Ultra Isolation Transformer

The core is constructed from low loss, cold rolled, grain oriented, annealed laminations of electrical sheet steel conforming to the latest international standards. Special frame is built in-house for clamping the core to reduce the magnetic noise as well as making the whole structure rigid and robust.

Coils are wound with paper covered electrolytic grade copper strip or synthetic enameled copper conductors. Cooling ducts are provided to keep the hot spot temperature as low as possible. Coils are dried in electric ovens. Rigid connection support and coil clamping is provided to ensure high short circuit strength.

Pre-compressed board PARMALI board and JAPANEESE insulation paper of best quality is used.

11. OIL
Oil tested for resistivity, dielectric and acidic characteristic conforming to IS 335. Before topping up oil is filtered throughly.

The tanks are made of M.S. steel plated / sheets with adequate bracing & stiffness. All the external surfaces are given a primary coat of Epoxy and finishing coat of Epoxy paint for better life.

AE meters and quality products for controls are used.

The table below gives approximate quantitative advantage of Automatic Voltage Controller at various fluctuation levels

% Reduction in Breakdown Possible Approx. Power Saving Possible
Input Voltage Variation Motor load below 10 Hp Lighting load Motor load below 10 Hp Lighting load
380 – 400 volts Nil Nil Nil Nil
380 – 420 volts 5% 10% 3% 5%
380 – 440 volts 10% 20% 5% 10%
380 – 460 volts 40% 40% 7% 20%
380 – 480 volts 60% 60% 10 30%

Comparison Between Power Make & Conventional Make Automatic Voltage Controller

  1. Power consumption is 0.5 to 1.5% depending upon the model and input voltage variation.
  2. Sutable for continuous 100% duty cycle.
  3. The carbon (graphite) Roller roll, while moving on the coil track, so contact Point of the roller goes on changing which prolongs the life of the rollers.
  4. Life at full load is 15-20 years.
  5. Negligible losses in full Buck / Boost Condition.
  6. Five years Unconditional warrantee in India

  1. Power consumption is 2 to 7% depending upon the model and input voltage variation.
  2. Sutable for continuous 30% to 40% duty cycle.
  3. Since the contact is by brush having flat surface, wear & tear of the brush is more and requires frequent replacement
  4. Maximum Life is 2-3 years at full load.
  5. Max losses in full Buck / Boost Condition.
  6. Normal warrantee for one year
Capacity Power make Roller type regulator losses Conventional make Carbon Brush type Dimmerstat losses
60 A 575 W 1050 W
75 A 730 W 2055 W
100 A 900 W 3105 W

Customized Automatic Voltage Controller for Various Industrial Use

750 KVA Automatic Voltage Controller
(Unbalanced Type + Isolation Transformer +
Complete ByePass Arrangement

3500 KVA Automatic Voltage Controller (Balance Type)

900 KVA Automatic Voltage Controller (Balance Type)

Complete Bye Pass Panel of
Automatic Voltage Controller
Capacity 1000 KVA