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华巨电子大功率NTC热敏电阻在电机软启动中的应用-华巨电子
1、概述 直流马达的工作等效电路如图1所示。稳态运行时，电枢回路方程为：
式中，U为直流马达供电电源电压；E为马达绕组上的反电动势；IR为绕组上的压降。起动瞬间，n=0，E=0，而R 很小，因此
式中，Ist为启动电流，将达到很大数值，通常为额定电枢电流的十几倍甚至更大，造成电网电压突然降低，影响电网。供电直流电源的规格要更大，以满足瞬间大电流冲击，同时也使马达本身遭受很大的电磁力冲击，严重时会损坏马达。因此，适当限制马达的启动电流是必要的。针对此问题，本研究提出了三种马达软启动方案：NTC(Negative Temperature Coefi—cient)热敏电阻软启动电路、MOSFET线性放大软启动电路、继电器延时软启动电路。三种方案的原理：启动瞬间，降低马达两端的启动电压，以较小的电流启动马达，使电机电流逐步上升到额定值，从而限制启动瞬问的大电流冲击。
2．1 NTC软启动电路 NTC thermistor是负温度系数热敏电阻，其电阻值随着温度的升高而降低，可有效抑制瞬间大电流冲击。由其组成的直流马达软启动电路如图2所示。把合适功率、阻值与温度系数的NTC串人马达的供电回路。当马达启动时，由于NTC以一定的阻值串人马达的供电回路，可以有效地把启动电流限制在规定范围之内。随着大电流的流过，NTC热敏电阻逐渐发热，阻值减小。当马达顺利起动后，NTC发热后，阻值很小，电能损耗较小。 3、实验分析 为了验证效果，马达回路串接NTC电阻和不接NTC电阻在同一负载(测试时电机的扭矩为63 kg·cm)下进行了实验，图5、图6分别为不接NTC、接NTC时马达绕组的冲击电流波形。从图中可以看出，启动瞬间，加了软启动电路的电流仅为未加软启动电路的1／4，可以有效抑制启动电流。这个电路的特点是简单、价廉，但当马达频繁起动时，限流效果较差，因为此时NTC温度较高，阻值较小，达不到很好的限流效果，所以频繁启动的马达不宜采用此软启动电路。 
华巨电子推出的大功率NTC热敏电阻已经在电机软启动中开始广泛的应用主要型号有： 5.主要技术参数
型号 | R25 | 最大稳态电流 | 25℃下最大电流时近似电阻值 | 片径Φ | 耗散系数 | 热时间常数 | 工作温度 | （Ω） | （A） | （Ω） | （mm） | （mW/℃） | （S） | （℃） | 芯片直径：(13-35)mm | -55～+250 | | SCD-10R01.7 | 10 | 1.7 | 0.031 | 5 | 8 | 60 | SCD-20R01 | 20 | 1 | 0.47 | 5 | 8 | 60 | | SCD-1R09 | 1 | 9 | 0.032 | 13 | 13 | 63 | | SCD-1R39 | 1.3 | 9 | 0.042 | 13 | 13 | 63 | | SCD-1R59 | 1.5 | 9 | 0.043 | 13 | 13 | 63 | | SCD-2R58-13 | 2.5 | 8 | 0.048 | 13 | 13 | 63 | | SCD-3R08 | 3 | 8 | 0.052 | 13 | 13 | 63 | | SCD-4R07 | 4 | 7 | 0.068 | 13 | 13 | 63 | | SCD-5R07 | 5 | 7 | 0.078 | 13 | 13 | 63 | | SCD-6R06 | 6 | 6 | 0.090 | 13 | 13 | 63 | | SCD-7R06 | 7 | 6 | 0.098 | 13 | 13 | 63 | | SCD-8R06 | 8 | 6 | 0.104 | 13 | 13 | 63 | | SCD-10R06 | 10 | 6 | 0.126 | 13 | 13 | 63 | | SCD-12R05 | 12 | 5 | 0.146 | 13 | 13 | 63 | | SCD-15R04 | 15 | 4 | 0.155 | 13 | 13 | 63 | | SCD-16R04 | 16 | 4 | 0.158 | 13 | 13 | 63 | | SCD-20R04 | 20 | 4 | 0.192 | 13 | 13 | 63 | | SCD-30R3.5 | 30 | 3.5 | 0.237 | 13 | 13 | 63 | | SCD-47R03 | 47 | 3 | 0.340 | 13 | 13 | 63 | | SCD-60R2.5 | 60 | 2.5 | 0.420 | 13 | 13 | 63 | | SCD-121R2.5 | 120 | 1.8 | 0.994 | 13 | 13 | 63 | | SCD-2R58-15 | 2.5 | 8 | 0.086 | 15 | 21 | 75 | | SCD-1R310 | 1.3 | 10 | 0.034 | 15 | 22 | 75 | | SCD-1R510 | 1.5 | 10 | 0.036 | 15 | 22 | 75 | | SCD-2R59.5 | 2.5 | 9.5 | 0.044 | 15 | 22 | 75 | | SCD-3R09 | 3.0 | 9.0 | 0.046 | 15 | 22 | 75 | | SCD-5R08 | 5.0 | 8.0 | 0.058 | 15 | 22 | 75 | | SCD-6R07 | 6.0 | 7.0 | 0.069 | 15 | 22 | 75 | | SCD-7R07 | 7.0 | 7.0 | 0.078 | 15 | 22 | 75 | | SCD-8R07 | 8.0 | 7.0 | 0.084 | 15 | 22 | 75 | | SCD-10R07 | 10.0 | 7.0 | 0.098 | 15 | 22 | 75 | | SCD-12R06 | 12.0 | 6.0 | 0.116 | 15 | 22 | 75 | | SCD-15R06 | 15.0 | 6.0 | 0.125 | 15 | 22 | 75 | | SCD-16R06 | 16.0 | 6.0 | 0.129 | 15 | 22 | 75 | | SCD-20R06 | 20.0 | 6.0 | 0.136 | 15 | 22 | 75 | | SCD-30R05 | 30.0 | 5.0 | 0.165 | 15 | 22 | 75 | | SCD-47R04 | 47.0 | 4.0 | 0.357 | 15 | 22 | 75 | | SCD-121R2.5 | 120 | 2.5 | 0.652 | 15 | 22 | 75 | SCD-0R716 | 0.7 | 16 | 0.026 | 20 | 29 | 110 | SCD-1R016 | 1.0 | 16 | 0.027 | 20 | 29 | 110 | SCD-1R020-20 | 1.0 | 20 | 0.020 | 20 | 29 | 113 | SCD-1R515 | 1.5 | 15 | 0.030 | 20 | 29 | 110 | SCD-2R014 | 2.0 | 14 | 0.035 | 20 | 29 | 110 | SCD-2R512 | 2.5 | 12 | 0.060 | 20 | 29 | 110 | SCD-2R513 | 2.5 | 13 | 0.055 | 20 | 29 | 110 | SCD-2R515 | 2.5 | 15 | 0.046 | 20 | 29 | 110 | SCD-3R012 | 3.0 | 12 | 0.040 | 20 | 28 | 110 | SCD-4R012 | 4.0 | 12 | 0.043 | 20 | 28 | 110 | SCD-4R712 | 4.7 | 12 | 0.046 | 20 | 28 | 110 | SCD-5R010 | 5.0 | 10 | 0.049 | 20 | 29 | 110 | SCD-5R012 | 5.0 | 12 | 0.047 | 20 | 29 | 110 | SCD-6R011 | 6.0 | 11 | 0.052 | 20 | 29 | 110 | SCD-6R810 | 6.8 | 10 | 0.055 | 20 | 29 | 110 | SCD-7R010 | 7.0 | 10 | 0.075 | 20 | 28 | 110 | | SCD-8R09 | 8.0 | 9 | 0.058 | 20 | 28 | 110 | SCD-10R08 | 10.0 | 8 | 0.085 | 20 | 29 | 110 | SCD-12R07.5 | 12.0 | 7.5 | 0.112 | 20 | 29 | 110 | SCD-15R07 | 15.0 | 7 | 0.123 | 20 | 29 | 110 | SCD-18R07 | 18.0 | 7 | 0.122 | 20 | 29 | 110 | SCD-20R06 | 20.0 | 6 | 0.132 | 20 | 29 | 110 | SCD-20R07 | 20.0 | 7 | 0.122 | 20 | 29 | 110 | | SCD-25R06 | 25.0 | 6 | 0.168 | 20 | 29 | 110 | | SCD-30R06 | 30.0 | 6 | 0.195 | 20 | 29 | 110 | | SCD-47R05 | 47.0 | 5 | 0.325 | 20 | 29 | 110 | | SCD-120R03 | 120.0 | 3 | 0.658 | 20 | 29 | 110 | SCD-0R522 | 0.5 | 22 | 0.017 | 25 | 30 | 130 | SCD-0R722 | 0.7 | 22 | 0.018 | 25 | 30 | 130 | | SCD-1R020-25 | 1.0 | 20 | 0.021 | 25 | 30 | 130 | SCD-1R519 | 1.5 | 19 | 0.024 | 25 | 30 | 130 | SCD-2R018 | 2.0 | 18 | 0.026 | 25 | 30 | 130 | SCD-2R516 | 2.5 | 16 | 0.029 | 25 | 30 | 130 | SCD-3R015.5 | 3.0 | 15.5 | 0.032 | 25 | 30 | 130 | SCD-4R015 | 4.0 | 15 | 0.039 | 25 | 30 | 130 | SCD-4R714 | 4.7 | 14 | 0.044 | 25 | 30 | 130 | SCD-5R014 | 5.0 | 14 | 0.047 | 25 | 30 | 130 | SCD-6R812 | 6.8 | 12 | 0.061 | 25 | 30 | 130 | SCD-7R011 | 7.0 | 11 | 0.064 | 25 | 30 | 130 | SCD-8R010 | 8.0 | 10 | 0.079 | 25 | 30 | 130 | SCD-10R010 | 10.0 | 10 | 0.084 | 25 | 30 | 130 | SCD-12R09 | 12.0 | 9 | 0.102 | 25 | 30 | 130 | SCD-15R08 | 15.0 | 8 | 0.117 | 25 | 30 | 130 | SCD-18R08 | 18.0 | 8 | 0.125 | 25 | 30 | 130 | SCD-20R08 | 20.0 | 8 | 0.132 | 25 | 30 | 130 | SCD-0R530 | 0.5 | 30 | 0.013 | 30 | 40 | 190 | SCD-1R030 | 1.0 | 30 | 0.014 | 30 | 40 | 190 | SCD-1R525 | 1.5 | 25 | 0.016 | 30 | 40 | 190 | SCD-2R023 | 2.0 | 23 | 0.019 | 30 | 40 | 190 | SCD-2R520 | 2.5 | 20 | 0.023 | 30 | 40 | 190 | SCD-3R019.5 | 3.0 | 19.5 | 0.026 | 30 | 40 | 190 | SCD-4R019 | 4.0 | 19 | 0.031 | 30 | 40 | 190 | SCD-4R718 | 4.7 | 18 | 0.035 | 30 | 40 | 190 | SCD-5R017 | 5.0 | 17 | 0.037 | 30 | 40 | 190 | | SCD-6R017 | 6.0 | 17 | 0.042 | 30 | 40 | 190 | SCD-6R816 | 6.8 | 16 | 0.043 | 30 | 40 | 190 | SCD-7R015 | 7.0 | 15 | 0.044 | 30 | 40 | 190 | SCD-8R014 | 8.0 | 14 | 0.049 | 30 | 40 | 190 | SCD-10R013 | 10.0 | 13 | 0.056 | 30 | 40 | 190 | SCD-12R012 | 12.0 | 12 | 0.067 | 30 | 40 | 190 | SCD-15R011 | 15.0 | 11 | 0.078 | 30 | 40 | 190 | SCD-18R010 | 18.0 | 10 | 0.092 | 30 | 40 | 190 | SCD-20R09 | 20.0 | 9 | 0.113 | 30 | 40 | 190 | SCD-0R532 | 0.5 | 32 | 0.010 | 35 | 55 | 280 | SCD-1R032 | 1.0 | 32 | 0.011 | 35 | 55 | 280 | SCD-1R528 | 1.5 | 28 | 0.013 | 35 | 55 | 280 | SCD-2R025 | 2.0 | 25 | 0.017 | 35 | 55 | 280 | SCD-2R523 | 2.5 | 23 | 0.020 | 35 | 55 | 280 | SCD-3R022 | 3.0 | 22 | 0.023 | 35 | 55 | 280 | SCD-4R021 | 4.0 | 21 | 0.026 | 35 | 55 | 280 | SCD-4R720 | 4.7 | 20 | 0.029 | 35 | 55 | 280 | SCD-5R019 | 5.0 | 19 | 0.030 | 35 | 55 | 280 | SCD-6R818 | 6.8 | 18 | 0.035 | 35 | 55 | 280 | SCD-7R017 | 7.0 | 17 | 0.037 | 35 | 55 | 280 | SCD-8R016 | 8.0 | 16 | 0.041 | 35 | 55 | 280 | SCD-10R015 | 10.0 | 15 | 0.045 | 35 | 55 | 280 | SCD-12R014 | 12.0 | 14 | 0.051 | 35 | 55 | 280 | SCD-15R013 | 15.0 | 13 | 0.060 | 35 | 55 | 280 | SCD-18R011 | 18.0 | 11 | 0.072 | 35 | 55 | 280 | SCD-20R010 | 20.0 | 10 | 0.089 | 35 | 55 | 280 |
注：若非特别指出,R25的允许偏差为±20%。 华巨电子热敏电阻厂家：www.sinochip.net
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