Fuse Ratings in Amps
High Voltage HRC Fuse links suitable for distribution circuits and motor protection circuits. These are backup fuse links for protection of transformers, cables, capacitors and motors. The fuse finks are available in Various current ratings upto 12kV. Fuse links are also available for much higher voltages upto 36kV depending on the application. Megawin fuse links are available in i15 & DIN versions for application In Mr and Oil switches. Following features ensure quality protection In the distribution circuits :
• Superior performance from the highest breaking current down to Iow over current.
• Low Mc voltages permits usage In lower voltage levels.
• Striker pin provision for indication as well as Hip bar operation in witch fuses.
• Low cutoff and let through energy offers protection against the thermal and dynamic effects of high short circuit current.
• Special tag versions are available to suit customer needs and special applications.
• Fuse links conform to IEC-282, BS-2692, DIN43625 & IS-938S specifications.
FOR TRANSFORMER PROTECTION
Transformers draw very large currents when they are energised. In practice, the value of inrush current as a ratio of transformer rated current tends to fall with the increase of the kb rating. It is assumed that the transformer inrush current is equivalent to either 10 or to times the transformer full-load current for duration of 100 cosec. To withstand high In-rush current and for protection against short circuits, fuse elements have been rigidly mounted on an Insulating former Inside the fuse bads The fuse links have built-In features which are very useful during low over-current regions to cut off the supply when associated with switchfuse assembly having tripbar arrangements. Depending on the application of the fuse link whether in air or oil, different versions are available to suit customer requirement A table for selection of fuse links for different transformer ratings acts as a guideline.
FOR MOTOR PROTECTION
High voltage current limiting fuse links are used in conjunction with either air-break or vacuum contactors to protect three phase AC induction motors at line voltages up to 7.2 kV. These fuse links are subjected to onerous duties as the motors are switched ON and OFF repeatedly depending on the end application. Consequently the fuse elements undergo severe mechanical and thermal stresses. Special element design is adapted which has better thermal withstand and cyclic stresses. Extensive pulse tests have been carried out to ensure no nuisance operations occur. These fuselinks have built-in features which are useful during low overcurrent regions when fitted in avitchfuse assemblies. To achieve higher current ratings for large motors, fuse links are mounted in-groups of two or three and supplied as factory built integral design. During direct-on-line starting of motors, the surge current would typically be of the order of four to six times the full load current of the motor. In the case of other methods of starling, the surge current magnitude is not so high. Normally a factor of 1.9 Is used as a guide while selecting a fuse link rating. A selection chart shown in the subsequent page enables correct selection of motor fuse link.
FOR CAPACITOR PROTECTION
High voltage capacitors are used with large motors for improving the power factor and in the case of distribution circuits, capacitors are used for Improving the system power factor. As the cost of the system installation increases with the KVAR rating of the bank, It is necessary to protect the high voltage capacitors with the correct fuse link. Whenever the capacitors are switched on, high in-rush current flows for a short time. The fuse links must withstand this surge and offer protection against internal faults. Knowing the unit rating of the capacitor, the fuse.* rating can be selected from the graph provided here as a guideline. However in the event of large capacitor banks and multiple units, care should be taken during fuse selection, as adjacent units will try to discharge during switching. It Is advised to refer to the manufacturer with complete network details.
FOR VOLTAGE TRANSFORMER PROTECTION
Fuse links are available for various voltage ratings from 3.6 to 36kV upto 3.15 Amps. These fuse links are able to withstand high inrush current during VT switching ON. In the event of an internal fault inside VT, the fuse links limit the fault energy by acting as a switch. They are available for application both In Air as well as in Oil. Special sealing technique has been adapted on the metallic capping to prevent oil entry inside the fuse link.
Megawin fuse links are available in BS & DIN version for application in Air and Oil switches. Following features ensure quality protection in the distribution circuit.
Superior performance from the highest braking current down to low over current
Low Arc voltages permits usage in lower voltage levels
Striker pin provision for indication as well as trip bar operation in switch fuses
Low cutoff and let through energy offers protection against the thermal and dynamic effects of high short circuit current
Special tag versions are available to suit customer needs and special applications.
Voltage transformer protection
Fuse links conform to IEC-282, BS-2692, DIN43625 & IS-9385 specifications