Motor Protection Guide MOTOR PROTECTION TABLES Selection of Class RK5 Fuses (FLNR_ID / FLSR_ID / IDSR Series) or POWR-PRO® Class RK1 Fuses (LLNRK / LLSRK / LLSRK_ID Series) Based on Motor Full Load Amps Using AC Motor Protection Tables to Select Fuse Ratings MOTOR RUNNING PROTECTION (USED WITHOUT PROPERLY SIZED OVERLOAD RELAYS) MOTOR FULL-LOAD AMPS Time-delay RK1 and RK5 fuse ratings selected in accordance with the following recommendations also meet NEC® requirements for Motor Branch circuit and Short-Circuit Protection. TIME DELAY UL CLASS RK1 MOTOR SERVICE MOTOR SERVICE MOTOR SERVICE MOTOR SERVICE OR RK5 FUSE FACTOR LESS FACTOR LESS FACTOR OF 1.15 OR AMPERE RATING FACTOR OF 1.15 OR THAN 1.15 OR THAN 1.15 OR GREATER OR WITH GREATER OR WITH WITH TEMP. RISE WITH TEMP. RISE TEMP. RISE NOT TEMP. RISE NOT GREATER GREATER OVER 40°C. OVER 40°C. THAN 40°C. THAN 40°C Selecting Fuses for Motor Running Protection Based on Motor Horsepower ⁄ ⁄ ⁄ ⁄ 14 ⁄ 3 10 ⁄ 4 10 ⁄ 12 ⁄ 6 10 ⁄ 8 10 ⁄ 1 10 18 15 100 2 10 Motor horsepower and motor Full Load Amperes (FLA) shown are taken from NEC® Tables 430.248 through 430.250 covering standard speed AC motors with normal torque characteristics. Fuse ratings for motors with special characteristics may need to vary from given values. 1 11⁄ 8 11⁄ 4 14 ⁄ 10 11⁄ 2 1 6 ⁄ 10 1 8 ⁄ 10 2 2 1⁄ 4 21⁄ 2 2 8 ⁄ 10 3 3 2 ⁄ 10 3 1⁄ 2 4 4 1⁄ 2 5 5 6 ⁄ 10 6 6 1⁄ 4 7 71⁄ 2 8 9 10 12 15 17 1⁄ 2 20 25 30 35 40 45 50 60 70 75 80 90 100 110 125 150 175 200 225 250 300 350 400 450 500 600 If motor running protection will be provided by the fuses, select fuse ratings for correct type of motor from Motor Protection Table Columns headed, “Without Overload Relays.” If overload relays will provide principal motor running protection, select fuse ratings for correct type of motor from Motor Protection Table Columns headed, “Back-up Running Protection” or “With Overload Relays.” Fuse ratings selected from these columns coordinate with most UL Class 10 and 20 overload relays which covers over 90% of motor applications. Selecting Fuses for Motor Running Protection Based on Motor Actual Full Load Currents Better protection is achieved when fuse ratings are based on motor actual FLA obtained from motor nameplates. Locate motor nameplate FLA in the column appropriate for the type of motor and type of protection required. Then select the corresponding ampere rating of the fuse from the first column of that line. Motor Protection White Paper Download our white paper on motor protection at littelfuse.com/technicalcenter © 2014 Littelfuse POWR-GARD® Products BACK-UP MOTOR RUNNING PROTECTION (USED WITH PROPERLY SIZED OVERLOAD RELAYS) MOTOR FULL-LOAD AMPS 1 0.08-0.09 0.10-0.11 0.12-0.15 0.16-0.19 0.20-0.23 0.24-0.30 0.32-0.39 0.40-0.47 0.48-0.60 0.64-0.79 0.80-0.89 0.90-0.99 1.00-1.11 1.12-1.19 1.20-1.27 1.28-1.43 1.44-1.59 1.60-1.79 1.80-1.99 2.00-2.23 2.24-2.39 2.40-2.55 2.56-2.79 2.80-3.19 3.20-3.59 3.60-3.99 4.00-4.47 4.48-4.79 4.80-4.99 5.00-5.59 5.60-5.99 6.00-6.39 6.40-7.19 7.20-7.99 8.00-9.59 9.60-11.99 12.00-13.99 14.00-15.99 16.00-19.99 20.00-23.99 24.00-27.99 28.00-31.99 32.00-35.99 36.00-39.99 40.00-47.99 48.00-55.99 56.00-59.99 60.00-63.99 64.00-71.99 72.00-79.99 80.00-87.99 88.00-99.99 100.00-119.99 120.00-139.99 140.00-159.99 160.00-179.99 180.00-199.99 200.00-239.99 240.00-279.99 280.00-319.99 320.00-359.99 360.00-399.99 400.00-479.99 480.00-600.00 0.09-0.10 0.11-0.125 0.14-0.15 0.18-0.20 0.22-0.25 0.27-0.30 0.35-0.40 0.44-0.50 0.53-0.60 0.70-0.80 0.87-0.97 0.98-1.08 1.09-1.21 1.22-1.30 1.31-1.39 1.40-1.56 1.57-1.73 1.74-1.95 1.96-2.17 2.18-2.43 2.44-2.60 2.61-2.78 2.79-3.04 3.05-3.47 3.48-3.91 3.92-4.34 4.35-4.86 4.87-5.21 5.22-5.43 5.44-6.08 6.09-6.52 6.53-6.95 6.96-7.82 7.83-8.69 8.70-10.00 10.44-12.00 13.05-15.00 15.22-17.39 17.40-20.00 21.74-25.00 26.09-30.00 30.44-34.78 34.79-39.12 39.13-43.47 43.48-50.00 52.17-60.00 60.87-65.21 65.22-69.56 69.57-78.25 78.26-86.95 86.96-95.64 95.65-108.69 108.70-125.00 131.30-150.00 152.17-173.90 173.91-195.64 195.65-217.38 217.39-250.00 260.87-300.00 304.35-347.82 347.83-391.29 391.30-434.77 434.78-500.00 521.74-600.00 0-0.08 0.09-0.10 0.11-0.12 0.13-0.16 0.17-0.20 0.21-0.24 0.25-0.32 0.33-0.40 0.41-0.48 0.49-0.64 0.65-0.80 0.81-0.90 0.91-1.00 1.01-1.12 1.13-1.20 1.21-1.28 1.29-1.44 1.45-1.60 1.61-1.80 1.81-2.00 2.01-2.24 2.25-2.40 2.41-2.56 2.57-2.80 2.81-3.20 3.21-3.60 3.61-4.00 4.01-4.48 4.49-4.80 4.81-5.00 5.01-5.60 5.61-6.00 6.01-6.40 6.41-7.20 7.21-8.00 8.01-9.60 9.61-12.00 12.01-14.00 14.01-16.00 16.01-20.00 20.01-24.00 24.01-28.00 28.01-32.00 32.01-36.00 36.01-40.00 40.01-48.00 48.01-56.00 56.01-60.00 60.01-64.00 64.01-72.00 72.01-80.00 80.01-88.00 88.01-100.00 100.01-120.00 120.01-140.00 140.01-160.00 160.01-180.00 180.01-200.00 200.01-240.00 240.01-280.00 280.01-320.00 320.01-360.00 360.01-400.00 400.01-480.00 0-0.09 0.10-0.11 0.12-0.13 0.14-0.17 0.18-0.22 0.23-0.26 0.27-0.35 0.36-0.43 0.44-0.52 0.53-0.70 0.71-0.87 0.88-0.98 0.99-1.09 1.10-1.22 1.23-1.30 1.31-1.39 1.40-1.57 1.58-1.74 1.75-1.96 1.97-2.17 2.18-2.43 2.44-2.60 2.61-2.78 2.79-3.04 3.05-3.48 3.49-3.91 3.92-4.35 4.36-4.87 4.88-5.22 5.23-5.43 5.44-6.09 6.10-6.52 6.53-6.96 6.97-7.83 7.84-8.70 8.71-10.43 10.44-13.04 13.05- 15.21 15.22-17.39 17.40-21.74 21.75-26.09 26.10-30.43 30.44-37.78 37.79-39.13 39.14-43.48 43.49-52.17 52.18-60.87 60.88-65.22 65.23-69.57 69.58-78.26 78.27-86.96 86.97-95.65 95.66-108.70 108.71-130.43 130.44-152.17 152.18-173.91 173.92-195.62 195.63-217.39 217.40-260.87 260.88-304.35 304.36-347.83 347.84-391.30 391.31-434.78 434.79-521.74 littelfuse.com Motor Protection Guide MOTOR PROTECTION TABLES Selection of Class RK5 Fuses (FLNR_ID / FLSR_ID / IDSR Series) or POWR-PRO® Class RK1 Fuses (LLNRK / LLSRK / LLSRK_ID Series) Based on Motor Horsepower MOTOR HP FULL LOAD AMPS ⁄ ⁄ 13 ⁄ 12 ⁄ 3 4 ⁄ 1 11⁄2 2 4.4 5.8 7.2 9.8 13.8 16 20 24 ⁄ ⁄ 13 ⁄ 12 ⁄ 3 4 ⁄ 1 12 1⁄ 2 3 5 71⁄2 10 2.2 2.9 3.6 4.9 6.9 8 10 12 17 28 40 50 ⁄ ⁄ 1 11⁄ 2 2 3 5 7 1⁄2 10 15 20 25 30 40 50 60 75 100 125 150 2.5 3.7 4.8 6.9 7.8 11 17.5 25.3 32.2 48.3 62.1 78.2 92 120 150 177 221 285 359 414 ⁄ ⁄ 1 11⁄ 2 2 3 5 7 1⁄2 10 15 20 25 30 40 50 60 75 100 125 150 200 2.2 3.2 4.2 6.0 6.8 9.6 15.2 22 28 42 54 68 80 104 130 154 192 248 312 360 480 16 14 16 14 12 3 4 12 3 4 WITHOUT OVERLOAD WITH OVERLOAD RELAYS RELAYS S.F. = LESS S.F. = LESS SWITCH OR S.F. = 1.15 OR S.F. = 1.15 OR THAN 1.15 OR THAN 1.15 OR FUSE CLIP MORE, TEMP MORE, TEMP TEMP RISE TEMP RISE RATING RISE NOT RISE NOT MORE THAN MORE THAN OVER 40°C OVER 40°C 40°C 40°C 120 VOLT 1-PHASE MOTORS (120V CIRCUIT) 5 5 5 6 ⁄ 10 7 6 1⁄4 7 1⁄2 9 8 9 12 10 15 15 15 17 1⁄2 20 171⁄2 20 25 20 25 30 25 30 230 VOLT 1-PHASE MOTORS (240V CIRCUIT) 2 1⁄2 2 1⁄2 2 8 ⁄ 10 3 1⁄2 3 2 ⁄ 10 4 4 1⁄2 4 4 1⁄2 5 6 ⁄ 10 5 6 ⁄ 10 6 1⁄4 8 7 1⁄2 9 10 9 10 12 10 15 15 12 15 12 20 17 ⁄ 25 35 30* 35 50 45 50 60 50 70 200 VOLT 3-PHASE MOTORS (208V CIRCUIT) 3 2 8 ⁄ 10 3 2 ⁄ 10 4 1⁄2 4 5 6 5 6 ⁄ 10 6 1⁄4 8 7 1⁄2 7 1⁄2 9 8 10 12 12 15 20 20 25 30* 25* 35 40 35 45 60 50 70† 75 70 80 90 80 100 110 100* 125 150 125 150 175 150 200 200* 200* 225 250 250 300 350 300 400 400* 400* 450 500 450 600 230 VOLT 3-PHASE MOTORS (240V CIRCUIT) 2 8 ⁄ 10 2 1⁄ 2 2 8 ⁄ 10 4 3 1⁄2 4 5 4 1⁄2 5 6 ⁄ 10 7 1⁄ 2 6 1⁄4 7 1⁄2 8 7 1⁄2 9 12 10 12 12 12 17 ⁄ 17 ⁄ 20 25 25 30 35 30* 35 50 45 60 60* 60* 70 80 75 90 100 90 100 125 110 150 150 150 175 175 175 200 225 200* 250 300 250 350 350 350 400 450 400* 450 600 500 600 © 2014 Littelfuse POWR-GARD® Products 5 6 ⁄ 10 7 9 12 17 1⁄2 20 25 30 30 30 30 30 30 30 30 30 2 8 ⁄ 10 3 1⁄2 41⁄2 6 8 10 12 15 20 35 50 60 30 30 30 30 30 30 30 30 30 60 60 60 3 4 1⁄ 2 6 8 9 15 25 30* 40 60 75 90 110 150 175 225 300 350 450 500 30 30 30 30 30 30 30 60 60 60 100 100 200 200 200 400 400 400 600 600 2 8 ⁄ 10 4 5 71⁄2 8 12 17 1⁄2 30 35 50 70 80 100 125 150 200 225 300 400 450 600 30 30 30 30 30 30 30 30 60 60 100 100 100 200 200 200 400 400 400 600 600 MOTOR HP FULL LOAD AMPS ⁄ ⁄ 1 12 1⁄ 2 3 5 71⁄2 10 15 20 25 30 40 50 60 75 100 125 150 200 1.1 1.6 2.1 3.0 3.4 4.8 7.6 11 14 21 27 34 40 54 65 77 96 124 156 180 240 ⁄ ⁄ 1 12 1⁄ 2 3 5 7 1⁄2 10 15 20 25 30 40 50 60 75 100 125 150 200 0.9 1.3 1.7 2.4 2.7 3.9 6.1 9 11 17 22 27 32 41 52 62 77 99 125 144 192 12 3 4 12 3 4 WITHOUT OVERLOAD WITH OVERLOAD RELAYS RELAYS S.F. = LESS S.F. = LESS SWITCH OR S.F. = 1.15 OR S.F. = 1.15 OR THAN 1.15 OR THAN 1.15 OR FUSE CLIP MORE, TEMP MORE, TEMP TEMP RISE TEMP RISE RATING RISE NOT RISE NOT MORE THAN MORE THAN OVER 40°C OVER 40°C 40°C 40°C 460 VOLT 3-PHASE MOTORS (480V CIRCUIT) 14 ⁄ 10 11⁄4 14 ⁄ 10 2 18 ⁄ 10 2 2 1⁄2 21⁄4 2 8 ⁄ 10 12 2 10 3⁄ 3 ⁄ 4 4 3 1⁄2 4 1⁄2 6 10 5 ⁄ 5 6 9 8 10 12 12 15 171⁄2 15 17 1⁄2 25 20 30 30* 30* 35 40 35 45 50 45 50 60* 60* 70 80 70 90 90 80 100 110 110 125 150 125 175 175 175 200 225 200* 225 300 250 300 575 VOLT 3-PHASE MOTORS (600V CIRCUIT) 11⁄8 1 11⁄8 16 ⁄ 10 14 ⁄ 10 16 ⁄ 10 8 10 2 1⁄ 2 1⁄4 3 2 1⁄2 3 3 2 ⁄ 10 2 8 ⁄ 10 31⁄2 12 4⁄ 4 5 7 1⁄2 7 8 10 10 12 12 12 15 20 17 1⁄2 25 25 25 30 30* 30* 35 40 35 40 50 45 60 60 60 70† 75 70 80 90 80 100 110 110 125 150 125 175 175 150 200 225 200* 250 14 ⁄ 10 2 2 1⁄2 3 1⁄2 4 5 6 ⁄ 10 9 15 17 1⁄2 25 35 40 50 60* 75 90 125 150 200 225 300 30 30 30 30 30 30 30 30 30 30 60 60 60 100 100 100 200 200 200 400 400 11⁄8 16 ⁄ 10 2 3 2 10 3 ⁄ 41⁄2 7 1⁄2 12 15 20 30 35 40 50 60 75 90 125 150 175 225 30 30 30 30 30 30 30 30 30 30 30 60 60 60 60 100 100 200 200 200 400 NOTES S.F. = Motor Service Factor * Fuse Reducers Required † 100 Amp Switch Required Motor Protection White Paper Download our white paper on motor protection at littelfuse.com/technicalcenter 2 littelfuse.com Motor Protection Guide MOTOR PROTECTION TABLES Selection of POWR-PRO® Class J Fuses (JTD_ID / JTD Series) Based on Motor Full Load Amps MOTOR F.L.A. JTD_ID / JTD AMPERE RATING 0.00 – 0.60 0.61 – 0.80 0.81 – 1.00 1.01 – 1.20 1.21 – 1.65 1.66 – 2.00 2.01 – 2.40 2.41 – 3.30 3.31 – 4.10 4.11 – 4.90 4.91 – 6.40 6.41 – 8.00 8.01 – 9.80 9.81 – 12.0 8 ⁄ 10 1 11⁄4 1 1⁄2 2 2 1⁄2 3 4 5 6 8 10 12 15 MOTOR F.L.A. JTD_ID / JTD AMPERE RATING MOTOR F.L.A. JTD_ID / JTD AMPERE RATING 12.1 – 14.5 14.6 – 17.0 17.1 – 21.0 21.1 – 25.0 25.1 – 28.5 28.6 – 34.0 34.1 – 37.0 37.1 – 41.0 41.1 – 48.0 48.1 – 52.0 52.1 – 59.0 59.1 – 66.0 66.1 – 76.0 17 1 /2 20 25 30 35 40 45 50 60 70 80 90 100 76.1 – 84.0 84.1 – 90.0 90.1 – 102 103 – 125 126 – 144 145 – 162 163 – 180 181 – 204 205 – 240 241 – 288 289 – 312 313 – 360 361 – 432 110 125 150 175 200 225 250 300 350 400 450 500 600 NOTE: For severe motor starting conditions, fuses may be sized up to 225% motor F.L.A. (See NEC ® Article 430.52 for Exceptions) Selection of CCMR Time-Delay Fuses Based on Motor Full Load Amps MOTOR FULL LOAD CURRENT (F.L.A.) FOR MOTORS WITH AN ACCELERATION TIME OF 2 SECONDS OR LESS MIN. F.L.A. (1) 0.2 0.3 0.4 0.5 0.6 0.8 0.9 1.1 1.2 1.5 1.8 2.1 2.3 2.6 2.9 3.3 3.5 3.6 4.1 4.3 4.6 5.2 5.8 6.9 8.9 11.5 14.3 20.7 23.7 26.6 30.0 35.5 MAX F.L.A. (3) 0.2 0.4 0.6 0.7 1.0 1.1 1.3 1.4 2.1 2.6 3.0 3.4 3.9 4.3 4.8 5.2 5.4 5.7 5.8 6.2 6.9 7.7 8.9 10.0 13.5 15.8 17.8 23.3 26.7 30.0 33.3 40.0 FOR MOTORS WITH AN ACCELERATION TIME OF 5 SECONDS OR LESS MIN. F.L.A. (1) 0.2 0.3 0.4 0.5 0.6 0.8 0.9 1.1 1.2 1.5 1.8 2.1 2.3 2.6 2.9 3.3 3.5 3.6 4.1 4.3 4.6 5.2 5.8 6.9 8.9 11.2 (2) 13.4 (2) 16.1 18.4 20.7 23.0 27.6 MAX F.L.A. (3) 0.2 0.4 0.5 0.6 0.9 1.0 1.1 1.2 2.1 2.6 3.0 3.2 3.3 3.4 3.7 4.0 4.1 4.2 4.3 4.6 5.2 5.8 6.6 7.7 10.0 11.8 13.4 17.9 20.5 23.1 25.6 30.1 1 Based on NEC ® requirement limiting the rating of time-delay fuses to 175% of motor F.L.A., or next higher rating. 2 Based on NEC ® exception permitting fuse rating to be increased, but not to exceed, 225% motor F.L.A., however per NEC ® Article 430.52 Class CC (0-30) fuses can now be sized up to 400% of motor F.L.A. 3 Based on Littelfuse CCMR time-delay characteristics. FOR MOTORS WITH AN ACCELERATION TIME OF 8 SECONDS OR LESS MIN F.L.A. (2) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.2 1.4 1.6 1.8 2.0 2.3 2.5 2.7 2.8 3.2 3.4 3.6 4.0 4.5 5.4 6.7 6.8 9.0 10.0 15.6 17.8 20.0 22.3 26.7 CCMR AMPERE RATING MAX F.L.A. (3) 0.2 0.3 0.5 0.6 0.8 0.9 1.0 1.1 1.8 2.3 2.6 2.8 2.8 2.8 3.1 3.4 3.5 3.7 3.8 4.2 4.5 4.9 5.5 6.7 9.0 11.0 15.0 15.9 18.2 20.4 22.7 27.3 ⁄ ⁄ ⁄ 3 10 12 8 10 1 11⁄4 1 1⁄2 18 ⁄ 10 2 21⁄2 3 3 1⁄2 4 4 1⁄2 5 5 6 ⁄ 10 6 6 1⁄4 7 71⁄2 8 9 10 12 15 20 25 30 35 40 45 50 60 NOTE: These values were calculated for motors with Locked Rotor Current (LRA), not exceeding the following values: MOTOR F.L.A. 0.00 – 1.00 1.01 – 2.00 2.01 – 10.0 10.1 – 17.8 *LRA 850% 750% 650% 600% *If motor LRA varies from these values, contact Littelfuse. © 2014 Littelfuse POWR-GARD® Products 3 littelfuse.com