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Factors Affecting Constant Voltage Transformer
Servo Voltage Stebilizer

Factors Affecting Performance / Queries / Notes : 

1.) Selection of CVT : - The CVT power rating should match the maximum power of the load including the initial surge rating. The rating should also take into account the future expansion of the load. Viz. Addition of extra drive in a computer, extra lines on an epabx exchange etc. As there are a large variety of machines like Fax/Computers /EPABX available in the market with different features and power ratings it is essential to carefully select the CVT instead of generalizing that "A" rating of CVT is suitable for "B" equipment. Under - Specification of the load may result in collapsing of the CVT voltage under overload conditions (starting inrush) and the consequent "hanging" of computers/ microprocessor systems. In case of doubt it is advisable to select the next rating of CVT.

2.) CVT Voltages: - all specifications of the CVT are referred to the true RMS voltage, hence all measurements (in case of testing by user) must be made by using a True RMS meters. PUREVOLT CVT has a specially designed shielded and calibrated voltmeter.

3.) No load Operation Heating: - these ferroresonant transformer function at very high level of flux density and the resonating tank circuit is working all the time whether the load is connected or not. The no load current of the CVT are as high as 40% and therefore it heats up under no load conditions. It is therefore recommended that at least 25% of the rated load be connected at all times or , as with most equipment, The CVT switched off when not in use. Purevolt CVT is designed to work under the worst condition, that if from no load to full load and from minimum to max. voltage. Continuously at ambient up till 50 deg. C. the CVT should be kept in a manner so that heat dissipation is possible. (Do not keep it in an enclosed cabinet).

4.) Monitor Screen Shaking:- CVT is a frequency dependent system. At frequencies other than the specified range (49.5 to 50.5 Hz) the CVT's resonance circuit always tries to lock on the basic frequency. Monitors which have the scan frequency locked to the line frequency, may result in the continuous shaking of the raster. This phenomenon shall not be observed in monitors which have their raster scan frequency locked to the internal crystal. Monitor shaking may also observed in case where the CVT is kept in close proximity of the monitor. This is because the leakage flux from the CVT interferes with the electro magnetic deflection of the CRT. The CVT must therefore be kept approximately 1 meter away from the CRT and so oriented that the effect of leakage flux is minimum.

Caution:- because of the high leakage it is recommended that magnetic storage media/component/display devices be kept away from the CVT.

5.) Computer Keyboard "Hanging" :- In some computers, after connecting it to the CVT, during switch-on of heavy loads like Printers etc. the computer "Hangs". This is due to the malfunctioning of the SMPS of the computer. SMPS have a preset threshold on the 5 volts DC bus for "Power Good" signal. If the SMPS units are marginal in their power rating then a normal heavy load switch on will "Disable" the "Power Goods"

signal, which causes the computer to hang. to overcome this problem - the "Power Good "threshold of the SMPS needs readjustments. Even after this if the problem persists the SMPS rating needs to be looked into.

6.) Audible Noise:- all CVT's produce audible noise because of the fact that its secondary section is in resonance while in operation and hence the core(lamination) also tend to vibrate at the basic resonance frequency. The intensity and the frequency of this noise depends on the geometry of the core and its mass. The intensity of this noise is also directly proportional to the power rating of the CVT. The audible noise also increases for CVT's having a very close regulation tolerance and vice versa. PUREVOLT's CVT not only has a very good regulation under extreme load and voltage conditions but also ensures that this noise does not interfere with the normal working environment.

7.) Wider Input Line Voltage Range:- In order to control a wide line voltage fluctuations (beyond the specified range), a CVT of higher rating may be used.

8.) Operation with Motor Loads:- because of the current limiting effect special attention should be given when used with motor applications. In general the CVT must have a load rating nearly equal to the maximum power drawn during the starting cycle. In case of very high inductive motors the starting currents may vary from two to eight times the normal running rating of the motors.

9.) Effect of Temperature:- the output voltage may show a small change as the unit warms up to stable operating temperature. The change is approximately 1% for each 40 deg.C of temperature range.

10.)Output Voltage Setting:- because of the fact that the normal incoming frequency commonly prevalent is around 49.5 Hz and because of the change in voltage as the CVT reaches its stable operating temperature the CVT is adjusted at the factory to within plus 2% , minus 0% of the rated value, with rated nominal voltage at 50 Hz applied at the input and the full rated load at unity power factor applied at the output at room temperature.

11.)Neutral to Ground Bonding:- this is factory provided and is optional. The user may remove this bond and create his own neutral or use it in the floating output mode. In the floating output mode the CVT output also becomes shock proof.

12.) Effect of Load Power Factor:- the output voltage may vary from the name plate values at different power factors.

13.) Applications:- Telemetry equipment and systems, Supervisory Control & Data Acquisition systems, CNC Machines, Computers, Data Processing machines ,Colour Photography Labs, P A Systems, Telecommunications, Telex, TV ,VCR, Electronic ,Typewriter , Fax, EPABX Systems ,Desktop Publishing & Pre print systems. Bio-medical equipment like ultra sound machines, Centralized Monitoring systems, Computerized Medical Equipment ,etc.

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How does it Operates?      Maintenance CVT?

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Products Offered :
Industrial Servo Voltage Stabilizers SVS, Automatic Voltage Regulators / Stabilizers, IGBT based Online UPS   (Single/Three Phase), Sine Wave Online Ups (Single / Three Phase), Automatic and Manual Voltage Stabilizers/Regulators, Constant Voltage Transformers – CVT, Ferro Resonant Transformers, Isolation Transformers, Auto Transformers, Step Up Down Transformers, Line Interactive – Offline UPS, Ups with External Battery, Power Inverters, DC – AC Converters, Telecom Transformers, Sine Wave Inverters, Solar Products, Dimmerstat / Variable Test Panel, Variable Auto Transformers (Variacs)

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