1. Online type:

All the Soft Starter Controllers have motor overload protection. When the soft starter runs online, the soft starter controller can overload the motor and do not install the thermal overload relay. Because the current harmonic current after the SCR is very large, the electronic thermal overload relay can not be installed, otherwise the system can not work properly. Because SCR is more expensive and difficult to replace, in order to protect SCR, fast fuse must be used to prevent the short circuit of the soft starter from burning down the thyristor.

2. Bypass type:

The bypass operation soft starter can not run off the bypass electrical ac contactor, so there are two main connection schemes. The function of the electrical ac contactor on the soft starter is the same as that under the online operation mode. The emphasis is on the thermal relay, which is located in the lower port of the bypass electrical ac contactor, not through the starting current, especially the electronic thermal relay. The electric current harmonics after the soft starter can greatly disturb the electronic thermal relay and make the motor stop. In addition, because there is no need to install fast fuse in the short time operation of silicon controlled rectifier, no fast fuse is installed in the main wiring scheme.

3. Built-in bypass type:

Its main wiring is approximately the same as that on line. The advantage is that there is no need to install fast fuse for short time operation of SCR. The overload protection of the motor is realized by a soft starter controller. It not only exceeds the electronic thermal relay in function and performance, but also does not misoperate due to the harmonic current of the main circuit and the interference from the outside.