国内工控行业发展迅猛，现如今，大功率的电机启动，都采用了变频控制柜。星三角降压起动控制线路在以前变频器、软启动器等电子设备价格比较贵，技术比较落后的时候是一个最常用的的电工电路，随着科技的发展，这种启动方式有逐步被淘汰的趋势，但是该启动电路中应用的基本电路中的互锁、自锁、延时继电器，电机的绕组接法等，对于刚刚接触电路的朋友是一个很好的教材。
对于一些刚刚入门工控行业的新手来说，拿到了电机的功率表，对着功率进行接触器与热过载继电器的选型配置是一个比较头疼的事情，下面我们就以施耐德为例，介绍功率对应接触器与热过载继电器的选型。
| 电动机功率（KW） | In(A) | IrD(A) | 直线接法KM2型号 | 三角形接法KM3型号 | 星型接法KM1型号 | 热过载继电器型号 | 整定范围（A） |
| 1.5 | 3.5 | 2 | LC1-D09 | LC1-D09 | LC1-D09 | LRD-07C | 1.6-2.5 |
| 2.2 | 5 | 3 | LC1-D09 | LC1-D09 | LC1-D09 | LRD-08C | 2.5-4 |
| 3 | 6.6 | 4 | LC1-D09 | LC1-D09 | LC1-D09 | LRD-10C | 4-6 |
| 4 | 8.5 | 5 | LC1-D09 | LC1-D09 | LC1-D09 | LRD-12C | 5.5-8 |
| 5.5 | 11.5 | 6 | LC1-D09 | LC1-D09 | LC1-D09 | LRD-12C | 5.5-8 |
| 7.5 | 15.5 | 9 | LC1-D12 | LC1-D12 | LC1-D09 | LRD-14C | 7-10 |
| 9 | 18.5 | 11 | LC1-D18 | LC1-D18 | LC1-D09 | LRD-16C | 9-10 |
| 11 | 22 | 13 | LC1-D18 | LC1-D18 | LC1-D09 | LRD-16C | 9-13 |
| 15 | 30 | 16 | LC1-D25 | LC1-D25 | LC1-D12 | LRD-21C | 12-18 |
| 18.5 | 37 | 22 | LC1-D25 | LC1-D25 | LC1-D18 | LRD-22C | 17-25 |
| 22 | 44 | 26 | LC1-D32 | LC1-D32 | LC1-D18 | LRD-32C | 23-32 |
| 30 | 60 | 35 | LC1-D38 | LC1-D38 | LC1-D25 | LRD-35C | 30-40 |
| 37 | 72 | 40 | LC1-D50 | LC1-D50 | LC1-D32 | LRD-3357C | 37-50 |
| 45 | 85 | 47 | LC1-D65 | LC1-D65 | LC1-D40 | LRD-3359C | 48-65 |
| 55 | 105 | 58 | LC1-D65 | LC1-D65 | LC1-D40 | LRD-3359C | 48-65 |
| 75 | 138 | 78 | LC1-D95 | LC1-D95 | LC1-D50 | LRD-3363C | 63-80 |
| 90 | 170 | 99 | LC1-D115 | LC1-D115 | LC1-D65 | LRD-4365C | 80-104 |
| 110 | 205 | 118 | LC1-D150 | LC1-D150 | LC1-D80 | LRD-4367C | 95-120
|