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General
An Issue of Voltage Transformation
Power Solution

SERVO CONTROLLED AC VOLTAGE STABILIZERS

The problem of fluctuations in supply voltage is a menace to electrical and electronic equipment. The magnitude of a supply voltage should be reasonably constant to ensure long life of electrical equipments and optimum utilisation of production system.

'POWERTRON' Servo Controlled Voltage Stabilizers are high-speed electro-mechanical regulators that provide constant output voltage at pre-determined level. They yield an accurate and constant voltage. Stability in the output is achieved by means of closed loop system in which a fixed portion of the output is achieved by means of compared with a stable reference voltage. Any charge in the output voltage will generate an error voltage, which is amplified suitably and fed for corrective action (i.e. to lower or raise the output voltage as required). A solid state IC based electronic circuit in modular form assembled on glass apoxy PCB is used for this purpose.

The outstanding advantages offered by these stabilizers are:-

1. Extremely high efficiency.

2. Virtually zero waveform distortion.

3. Very low internal impedance.

4. Negligible phase shift.

5. No-effect on system power factor.

6. Insensitive to load magnitude & power factor.

7. A close accuracy of the output voltage for all variations of line voltage or load current within the specified range of the stabilizer.

8. Fast correction rate.

The stabilizer operates on the servo-driven, buck boost principle. Each of them essentially consists of a continuously variable autotransformer, a servo motor and a solid state electronic control unit. Depending upon the rating in KVA, the input voltage range and the nominal output voltage etc. the buck/boost transformer and auto-variable transformer are made in natural air-cooled or oil cooled construction.

CHOICE AVAILABLE

SINGLE PHASE : Designed for single phase A.C. Supply.

THREE PHASE (BALANCED UNIT): Designed of 3 phase applications where the input supply voltage and load is balanced. The system uses three variable transformers driven by a common servo-motor and sensing circuit. A selector switch selects any one of the 3 phases for sensing and correction. The two other phases follow the correction offered by the selected phase.

THREE PHASE (UNBALANCED UNIT): Designed for 3 phase unbalanced AC supply and load whereby three single phase units are connected in star configuration. Each unit individually takes care of its supply voltage and load fluctuations.

Non-standard voltage stabilizers to suit individual customer requirement can also be manufactured against specific requirements. For this following information is required with the enquiry.

No. of phases in the supply system.
Range of input voltage variation.
Nominal output voltage.
Capacity in KVA.
Max. current in any phase.
Speed of correction desired in volts/sec.
Size limitation, if any.
Desired optional features.
Any other features.

STANDARD FRONT PANEL CONDITIONS/INDICATORS
A voltmeter with switch to indicate both input & output voltage.
Indicating lamps to show what the input voltage is beyond the correction range of the unit.
Supply 'ON' indicator.
Control Switch-toggle switch with manual & automatic positions.
Raise/lower push buttons for manual adjustments of output voltage when the control switch is in manual positions.
Output level adjustment-knob control adjustable with the help of a screwdriver.

OPTIONAL FEATURES
Over voltage & under voltage protection, with this feature the unit will automatically switch off when the output voltage remains for certain time above or below a certain pre-set voltage limit.
Over-load protection to switch off the unit when the load current remains at a value higher than the rated one.
Remote control facility.
Single phase preventor (for 3 phase units).
Miniature/moulded case circuit breaker.
Switch fuse assembly at the input.
By-pass switch facility.
R.F. Interference filter.
Isolation transformer.
Separate voltmeters for input & output.
Ammeter for measurement of load current.
Digital panel meter.
Electronic audio alarm.
Earth leakage relay.

APPLICATIONS:

COMPUTERS: Data processing equipment, Micro processor based systems, peripherals like tape & disc devices, printers, card pushes, data terminals, word processor, calculating machines etc.

MACHINE TOOLS: NC/CNC/DNC/ Machine tools with sophisticated electronic control systems.

LABORATORY EQUIPMENTS: Spectrometers, electron microscopes, spectro photometers, chromatographs, photographic processing equipment etc.

MEDICAL ELECTRONIC EQUIPMENTS: CAT scanners, body scanners, X-ray machines, electro cardio-scopes, intensive care units sterilizers.

COMMUNICATION DEVICES: Radio transmitters, television cameras, video recorders, radar and navigational equipment.

GENERAL OFFICE EQUIPMENT: Duplicating machines photo copiers, telex machines, teleprinters, plain paper copiers etc.

PROCESS CONTROL SYSTEM : For chemical & pharmaceutical industries.

GENERAL: General heating, lighting, production & process control equipment, air-conditioning plants etc.



SPECIFICATIONS OF STANDARD MODELS
SYSTEM INPUT VOLTAGE RATING OUTPUT VOLTAGE
(STANDARD)
REGULATION
SINGLE PHASE 180 - 250V
OR
170 - 270V
1KVA TO 100 KVA 230V

230V
+/-1% OR +/- 0.5%

+/-1% OR +/- 0.5%
THREE PHASE
(BALANCED)
360 - 440V
OR
315 - 440V
OR
340 - 480V
1.5 KVA TO 800KVA

1.5 KVA TO 500KVA
415V

415V
+/-1% OR +/- 0.5%

+/-1% OR +/- 0.5%
THREE PHASE
(UNBALANCED)
360 - 440V
OR
315 - 440V
OR
340 - 480V
OR
300 - 470V
1.5 KVA TO 800KVA

1.5 KVA TO500KVA

1.5 KVA TO 800KVA
415V

415V

415V
+/-1% OR +/- 0.5%

+/-1% OR +/- 0.5%

+/-1% OR +/- 0.5%

An Issue of Voltage Transformation

The quality of incoming power has deteriorated to such an extent that today it is impossible to work without one form of power conditioning or other. Inexpensive and rugged, the CVT has proved to be a reliable device for power conditioning.

All modern day electronic equipment including telemetry equipment and system, computerised medical equipment, data processing machines, TVs, VCRs, electronic type writers, FAX machines EPABX systems, DTP and pre-print systems, CC machines, colour photography labs, PA systems, telecommunication system, bio-medical Equipment (Ultra sound machines, centralised monitoring system) etc. is designed to operate on a steady sine wave of 220/230V RMS.

But the incoming power is not always suited to the requirement of your machine. Over-voltages, under-voltages, spikes, surges - all these can cause serious damage to electronic equipment. Infact the quality of incoming power has deteriorated to such an extent that today it is impossible to work without one form of power conditioning equipment or the other. With these devices you protect not only your computers but your complete investment. Besides data costs many times more in terms of money, time and frustration. Power protection thus is like insurance - a trade off between risk and cost.

The snag usually arise when impulses generated externally travel through the effective impedance of the copper wire. Although these have a damping effect on the disturbances, the actual problem comes up due to the simultaneous use of other
electrical equipment such as air conditions, motorises machines, heavy equipment, chokes and other such equipments , which draw heavy surge currents. These currents are potential hazards to all microprocessor-based equipment.

A difficulty may also arise from over-loading of the supply. For example the wiring in a particular area may have been designed to handle 'A' watts of power. But the actual power, which is being handled by these wires, is to the tune of 3A watts. The result is low voltage during peak load hours and very high voltage during off load hours. This is extremely harmful to microprocessor-based equipment.

An equipment providing protection against these problems by supplying regulated power to microprocessor based equipment is the CVT. A constant voltage transformer regulates voltage variation, suppresses transients (isolation) and bridges short interruption/dips.

 

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