Internal and external methods of soft start

Speaking of electric motors, there are many ways to start them. The most efficient way is to start directly, but direct start will have an impact on the entire power supply network (except when the power supply is sufficient). In order to reduce the impact on the power grid, many methods such as star-delta, soft start, and frequency converter are currently used. The early series resistance and auto-coupling step-down are rarely used. But now more commonly used is the soft start method. Today, the soft start cabinet manufacturer will introduce the internal and external methods of soft start to you.

"External" is to connect the power components of the soft starter to the outside of the delta-connected motor to control the line current returned by the motor. "Internal connection" is to connect the power components of the soft start to the inside of the delta-connected motor, and control the phase current of the delta-connected motor. Answer Since the line current is 1.73 times the phase current, the same soft starter can increase the control current (power) by 1.73 times when it is "internally connected".

To judge whether the soft start is connected internally or externally, the direct way is to observe how many wires are connected to the motor being controlled. 3 wires are connected externally; 6 wires are connected internally. Do not observe the wiring of the soft starter, because it is easy to misread it because the soft starter is equipped with an external bypass contactor. Whether to use internal or external connection depends on the situation on site, as well as cost factors. After all, the motor is connected to the soft starter with six cables. Generally speaking, if the soft-start control cabinet is next to the motor, it can be considered to be connected internally, but in practical applications, it is almost impossible for the soft-start cabinet and the motor to co-exist in the same room. First, the motor vibrates too much; It is not conducive to the centralized management of power distribution cabinets. Fourth, the wiring is too troublesome.