Introduction
Unistar medium voltage All Polypropylene capacitors are proven products of Universal Cables Ltd. Low operating stresses, lower temperature rise and losses make them superior to any other type of capacitors. Absence of paper reduces the chances of gas formation, bulging and bursting.
This makes All PP capacitors almost fire proof. These capacitors are best suited for systems which have high and frequent voltage fluctuations and harmonics caused on account of diodes, thyristors and other non-linear loads. Seperate aluminium foil used as electrode, enhances it;'s capacity to withstand high inrush current, associated with parallel switching, likes of which we come across in automatic power factor correction schemes. That is why in industrial applications All PP capacitors are fast replacing Mixed Dielectric and other types of capacitors.
Technology
UCL has been making All PP capacitors as per the technology provided by General Electric Co. of U.S.A. So far, these capacitors were made in high voltage range. Now Universal Cables Limited has extended this technology to medium voltage range. Further improvements have been achieved by introducing extended foil design which gives firm internal connection, lower internal resistance and inductance, and high inrush current withstanding capabilities. All the sophistication and care required for high voltage capacitors gets passed on to these capacitors as well, which makes them the most superior capacitors in the medium voltage range.
Manufacturing Process
Unistar All PP dielectric capacitors consists of number of basic elements which are constructed by winding layers of aluminium foil, interleaved by bi-axially oriented polypropylene film. Internal fuses are provided with each element. The winding is carried out in an air conditioned room equipped with special filters to provide dust- free atmosphere, which is very vital for capacitors. Elements thus formed are connected in parallel and then in delta. the complete pack is inserted in a steel case and 3 terminals are brought out through suitable bushings. Capacitors are put under vacuum drying and then impregnated with non-PCB non-toxic oil. After removing from the vacuum tank, units are sealed and then sent for routine electrical testing, painting and assembly. Periodically, few units are taken out from manufacturing process and are subjected to rigorious type testts to ensure quality standards.
Accessories
Capacitor Units are provided with terminal cover to enclose live parts. Entry hole is provided for the bottom entry of the cable. In case of banks, base channel to mount the capacitors, common terminal cover and a set of aluminium busbars are provided. Cable glands are provided on request.
Mechanical Configuration
Non Standard Kvar and Voltage ratings can be provided on request
Detailed Specifications
Reference Standard :
IS 2834 - 1986
Upper Limit of Temperature Category
50 C . As per IS which means
Mean over 1 hour ... 50 C
Mean over 24 hours... 45 C
Mean over 1 year ... 35 C.
Location : Indoor
No. of Phases, frequency
3, 50 Hz
Connection internal delta
Tolerance -5% to +10 %
a) Unit 0% to +10%
b) Bank
Discharge
resistors across terminals to discharge to 50 V in less than 60 seconds .
Overload Capacity
110% of the rated voltage or
130% of the rated current or
130% of the rated output.
Protection
Internal element fuses.
Finish
Light grey enamel paint of shade 631 of IS 5
Maximum allowable temperature
15 C above ambient.
