R-RATED MEDIUM VOLTAGE FUSES FOR MOTOR CIRCUITS Medium Voltage “R” Rated Fuses for 2.4 and 4.8 kV Motors List of Ratings 2.4 kV System Voltage Catalog Symbol 2.75 VFRHA 2R 2.75 VFRHA 3R 2.75 VFRHA 4R 2.75 VFRHA 6R 2.75 VKRHA 9R 2.75 VKRHA 12R 2.75 VKRHK 18R 2.75 VKRHK 24R 4.8 kV System Voltage Current Rating Amperes at 40°C 70 100 130 170 200 230 390 450 Figure Number Catalog Symbol 5.5 VFNHA 2R 70 5.5 VFNHA 3R 100 5.5 VFNHA 4R 130 5.5 VFNHA 6R 170 5.5 VKNHA 9R 200 5.5 VKNHA 12R 5.5 VKNHK 18R 5.5 VKNHK 24R 5.5 VKNHK 30R 5.5 VKNHK 36R 5.5 VKNHK 40R 5.5 VKNHK 48R 1 2 Current Rating Amperes at 40°C Figure Number 3 230 390 450 450 500 600 650 4 Notes: 1. Interrupting rating - 80,000 amperes asymmetrical 60Hz. 2. These fuses are dimensionally interchangeable with corresponding R-Rated fuses produced by other leading North American manufacturers. Dimensions 3" 76.2mm 10.88" 276.0mm .63" max. 16.0mm 3" 76.2mm Figure 1 3" 76.2mm 10.88" 276.0mm 15.88" 403.0mm .63" max. 16.0mm Figures 1 & 3 Figure 3 .63" max. 16.0mm 3" 76.2mm 15.88" 403.0mm 3" 76.2mm .63" max. 16.0mm 3" 76.2mm 6.31" 160.0mm Figure 2 114 Figure 4 Figures 2 & 4 R-RATED MEDIUM VOLTAGE FUSES FOR MOTOR CIRCUITS Medium voltage fuses for motor circuits offer the following user benefits: • Performance complies with latest ANSI Standards • Dramatic reduction in energy let-thru • Lower power dissipation • Low arc voltage during operation • Low minimum breaker current values • Includes heavy duty striker to IEC 282-1 ADVANTAGES OF EDISON MOTOR FUSES During the full voltage starting of motors the fuse elements reach a considerably higher temperature than normally occurs under continuous operation. The resulting expansion and contraction of the fuse element can cause premature operation. The Edison motor circuit fuse incorporates provisions in the design of the element to minimize this effect and hence avoid the necessity of having to use a much larger size of fuse. Edison fuses operate very quickly on heavy fault currents. This results from the steepness of the time/current characteristic, which also facilitates co-ordination with the other components of the circuit. Lower power dissipation helps to ensure low temperature rise of, for example, multi-tier starters. MOTOR STARTING APPLICATION Application Procedure For any motor the fuse current rating is determined by magnitude and duration of starting current, except in a few situations where the starting conditions are very light. The fuse current rating should be selected as follows. Direct On-Line Starting In the absence of specific information the starting current can usually be taken to be six times the motor full load current. The starting time will depend on the type of drive but will be approximately as follows: Pump Motors - 6 seconds Mill Motors - 10 to 15 seconds Fan Motors - 60 seconds These are average values and the appropriate figures for starting current and starting time for the actual installation should be obtained wherever possible. Multiply the starting current by 1.6 and using this value of current and the starting time (it is recommended that a minimum time of 8 seconds be adopted) plot this point on the minimum melting time-current characteristics of the fuses. The correct current rating of fuse is then chosen as being the one immediately to the right of the point so plotted. The chosen fuse must also have a current rating of at least 1.3 times the full-load current of the associated motor. Switching (arc) voltages are appreciably less than permitted values and fall with lower values of system voltage. Thus the 5.5kV fuses are equally suitable for use in 4.8kV, 4.16kV and 2.4kV circuits. The rating thus chosen will be adequate for normal applications where the associated motor is not started more than twice in any given period of one hour. For applications involving more frequent starting duties, a greater derating factor must be applied as shown in the following table. The superior low-overcurrent breaking performance is of advantage whether or not the striker is used to open the contactor. DERATING FACTOR “R” RATING The “R” rated motor circuit fuses should be selected to coordinate with the motor and controller to provide short circuit protection. The actual “R” rating signifies a 20 second blow point at 100 times the “R” rating of the fuse. For example: 2R fuse opens in 20 seconds at 200 amperes. 12R fuse opens in 20 seconds at 1200 amperes. Maximum of 2 starts per hour Derating factor 1.6 Maximum of 4 starts per hour Derating factor 1.7 Maximum of 8 starts per hour Derating factor 2.0 Maximum of 16 starts per hour Derating factor 2.2 The figures in the above table apply only when the Minimum Melting Time Current Characteristic Curve is used. For applications involving more frequent starting duty than 16 times per hour or where unusual duty cycles are involved consult Edison Fusegear for advice. Assisted Starting A similar method of fuse selection may be used as for direct-on-line starting (see above) but it must be noted that the normal running current of the motor is likely to be closer in value to the nominal current rating of the fuse than for direct-on-line applications. The rating of fuse chosen will need to be appreciably greater than the motor running current to allow for restricted cooling inside control gear cubicles, particularly where multitier starters are involved. In case of doubt refer to Edison Fusegear for further guidance. 115 R-RATED MEDIUM VOLTAGE FUSES FOR MOTOR CIRCUITS Time-Current Characteristics for 5.5 kV and 2.75 kV Fuses. TIME IN SECONDS 100 10 1 .1 .01 100 2 Total Clear 6 9 12 1,000 18 24 30 36 40 48 10,000 "R" RATING G8690D 100,000 100 10 1 .1 .01 TIME IN SECONDS 100 3 4 6 9 12 1,000 18 24 30 36 40 48 10,000 100,000 "R" RATING G8691D Minimum Melt 2 RMS SYMMETRICAL CURRENT IN AMPERES 116 RMS SYMMETRICAL CURRENT IN AMPERES Time-Current Characteristics 3 4 R-RATED MEDIUM VOLTAGE FUSES FOR MOTOR CIRCUITS Peak Let-Through Current Curve (5.5kV and 2.75kV Fuses) 48 40 36 30 24 18 12 9 6 4 3 2 10 "R" RATING PEAK CURRENT (KA) 100 10 1 .1 .1 1 PROSPECTIVE CURRENT (SYM. RMS KA) Application for HV Motor Circuit Fuses The following table is a general guide only based on a number of assumptions regarding the motor duty application which are listed below. Contact Edison Fusegear for specific application information. 2.4 KV FLC FUSE HP Amps “R” Amps 75 17 2R 70 100 22 2R 70 125 28 3R 70 150 33 3R 100 200 44 4R 130 250 55 6R 170 300 67 6R 170 350 78 9R 170 400 89 9R 200 500 111 12R 230 600 133 18R 390 700 155 18R 390 800 177 17R 390 900 200 18R 390 1000 222 24 450 1100 244 24R 450 1200 266 24R 450 1400 311 30R 450 1600 355 36R 500 1800 399 40R 600 1900 422 40R 600 2000 444 40R 600 2200 488 48R 650 2400 – – – 2600 – – – 2800 – – – 3000 – – – 3500 – – – 4000 – – – 4500 – – – Contact Edison for applications regarding other operating conditions. 4.16 KV FLC Amps – – 16 19 26 32 38 45 45 64 77 90 102 115 128 141 154 179 205 230 243 256 282 307 333 358 384 448 – – The application tables are based on the following assumptions: Motor Efficiency ---------Motor Power Factor ----Starting Current ---------Starts/Hour ---------------- FUSE “R” – – 2R 2R 3R 3R 4R 4R 4R 6R 9R 9R 9R 12R 18R 18R 18R 18R 18R 24R 24R 24R 30R 30R 36R 36R 36R 40R – – Amps – – 70 70 100 100 130 130 130 170 200 200 230 230 390 390 390 390 390 450 450 450 450 450 500 500 500 600 – – 90% Run Up Time ------ 10 Secs. 0.9 Starting Method -- Full Voltage 6 x FLC Min. Fuse Size---- 1.3 x FLC Max of 2/Hour 4.8 KV FLC Amps – – – 17 22 28 33 39 44 55 67 78 89 100 111 122 133 155 177 200 211 222 244 266 288 311 333 388 444 500 FUSE “R” – – – 2R 2R 3R 3R 4R 4R 6R 6R 9R 9R 9R 12R 12R 18R 18R 18R 18R 18R 24R 24R 24R 30R 30R 36R 36R 40R 48R Amps – – – 70 70 100 100 130 130 170 170 200 200 200 230 230 390 390 390 390 390 450 450 450 450 450 500 500 600 650 117

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