Why can the motor start only when the soft starter is reset?

- Oct 09, 2019-

The first thing to understand is "reset."In the electronic circuit, in order to make the microcomputer or microcontroller can work normally (including sequential digital circuit, clock signal circuit), when there are other problems in the process of operation, to restore its original state (or called initialization state), there is a manual reset on key.It works, on the RST pin of integrated circuit and integrated circuit of power supply between Vcc access a normally open button, when the fault occurs later generations to press a button, the voltage Vcc voltage directly to the RST side, the digital circuit caused by failure to release before stop vibration phenomenon, restores the initialization state to start work again.

The next step is to understand the construction of the soft starter.Soft starter is a 16-bit microcontroller as the core, plus a lot of signal acquisition sensors to intelligent control the motor.It can conduct stepless voltage regulation to the starting current required by the optimal motor.Simply put, it is a replacement for the traditional Y/ delta depression-actuating device.

Soft starter with the help of single-chip microcomputer for all-round control, it usually has the following functions;(1) self-check function.After the soft starter is powered on, the internal system will carry out self-inspection, and it will give an alarm immediately if there is any fault.(2) rated current setting.Once the rated current of the soft starter is determined, the tripping level of the electronic overload protector is also determined.(3) soft start function.When it receives the start command, it will automatically enter the start program and output a linearly rising voltage to the motor within a specified time (generally it can be set between 0.5 and 60s).The initial starting voltage is 10%~60% of the rated voltage of the motor, and the voltage after starting is the rated voltage of the motor.The starting voltage can be set on the operation panel before starting the operation, including the starting time.

Medium and large motors need energy saving start, and considering the initial investment, the power of the motor below 75KW using auto-buck Y/ delta start is more economical.It is more economical to use a soft starter for a motor with a power of 75~250KW.Under the condition of capricious economic conditions, the frequency converter can be directly selected to conduct the comprehensive start of frequency conversion and voltage reduction of the motor.The soft starter has strict requirements on the grid voltage. In general, the voltage drop is less than 10%Ue, which must be noted in the use process.

Because the soft starter set a lot of protection functions, including energy saving function, overheating protection function, two-way thyristor damage protection function, phase loss protection function and so on.Any link after a problem, its corresponding sensor will be timely feedback to the microcontroller chip, the chip issued instructions to automatically stop the circuit work.In general, the alarm signal sent by it has a corresponding fault code, so as to enable the operator to timely remove the fault and restart the work according to the instructions of the fault code.Failure is not eliminated, not reset, it will always be in the state of stop to ensure the safety of the motor.