電壓由零慢慢提升到額定電壓，這樣電機在啟動過程中的啟動電流，就由過去過載沖擊電流不可控制變成為可控制。并且可根據(jù)需要調(diào)節(jié)啟動電流的大小。電機啟動的全過程都不存在沖擊轉(zhuǎn)矩，而是平滑的啟動運行。這就是軟啟動。 [1] 
簡介編輯
a新穎電機控制裝置，國外稱為Soft Starter。它的主要構(gòu)成是串接于電源與被控電機之間的三相反并聯(lián)晶閘管及其電子控制電路。運用不同的方法，控制三相反并聯(lián)晶閘管的導(dǎo)通角，使被控電機的輸入
電壓按不同的要求而變化，就可實現(xiàn)不同的功能。軟起動器和變頻器是兩種完全不同用途的產(chǎn)品。變頻器是用于需要調(diào)速的地方，其輸出不但改變電壓而且同時改變頻率；軟起動器實際上是個調(diào)壓器，用于電機起動時，輸出只改變電壓并沒有改變頻率。變頻器具備所有軟起動器功能，但它的價格比軟起動器貴得多，結(jié)構(gòu)也復(fù)雜得多。電動機軟起動器是運用串接于電源與被控電機之間的軟啟動器，控制其內(nèi)部晶閘管的導(dǎo)通角，使電機輸入電壓從零以預(yù)設(shè)函數(shù)關(guān)系逐漸上升，直至啟動結(jié)束，賦予電機全電壓，即為軟啟動，在軟起動過程中，電機起動轉(zhuǎn)矩逐漸增加，轉(zhuǎn)速也逐漸增加。

The voltage is slowly increased from zero to the rated voltage, so that the starting current of the motor in the starting process is controllable from the uncontrollable overload impulse current in the past. And the starting current can be adjusted as needed. There is no impact torque in the whole process of motor starting, but smooth starting operation. This is soft start. [1] 
Introduction editor
A novel motor control device, called soft starter abroad. Its main composition is a three-phase anti parallel thyristor and its electronic control circuit connected in series between the power supply and the controlled motor. Different methods are used to control the conduction angle of the three-phase anti parallel thyristor to make the input of the controlled motor
Different functions can be achieved by changing the voltage according to different requirements. Soft starter and frequency converter are two completely different products. The frequency converter is used where speed regulation is required. Its output changes not only the voltage but also the frequency; The soft starter is actually a voltage regulator. When the motor is started, the output only changes the voltage without changing the frequency. The frequency converter has all the functions of soft starter, but its price is much more expensive than the soft starter, and its structure is much more complex. The motor soft starter uses the soft starter connected in series between the power supply and the controlled motor to control the conduction angle of its internal thyristor, so that the motor input voltage gradually rises from zero with a preset functional relationship until the end of starting, and gives the motor full voltage, that is, soft starting. In the process of soft starting, the motor starting torque gradually increases, and the speed also gradually increases.