Using a soft starter to misconception - Delixi

In the use of soft starters, some users often have some faulty concepts such as:

1. It is thought that whether the motor can start successfully is related to the function of the soft starter, and a good brand or even a foreign brand should be selected under heavy load.

2. When the motor cannot start the load, it is thought that the capacity of the soft starter is not enough, and the capacity of the soft starter should be increased.

3. I think that a certain starting method is particularly suitable for "heavy-load" starting.

4. The soft-starter with the smaller the starting current and the less voltage reduction in the power grid, the better the function.

Using a soft starter to misconception - Delixi

Using a soft starter to misconception - Delixi

The recognition of these faults is due to the lack of knowledge and awareness of the principle of the soft starter of the motor. Let's analyze the above problems one by one.

The first fault concept: whether the motor can be started successfully is related to the function of the soft starter. This problem should be analyzed in two aspects, first of all, it is necessary to see that the corresponding quality of a good brand is relatively good, so in terms of reliability, the probability of a good brand having a problem will be relatively small. However, in terms of the nature of the load of the starting motor, it is the starting torque of the motor that plays a decisive role, and as far as the motor torque is concerned, it is related to many factors. As a kind of voltage regulator, the motor soft starter can only change the control quantity of the motor stator voltage, and the motor torque is proportional to the square of the stator voltage, and the stator voltage is also changed to change the motor torque, this fundamental principle can not be changed, and the soft starters of various brands are designed according to this principle, and their product function or quality has nothing to do. Therefore, whether it is a domestic brand or a foreign brand, in the starting torque, it is fundamentally the same, as long as it is not a soft starter, if the motor can not start the load, it is useless to replace it with other better brand products.

The second fault concept: whether the motor can be started successfully is related to the capacity of the soft starter. In practice, the capacity of the soft starter and the capacity of the motor are mixed, or perhaps the capacity and drive torque are mixed, which are two different concepts in practice. As far as the motor is concerned, the capacity and the driving torque are necessarily the same, and the large capacity of the motor also reflects its ability to output a larger driving torque. The same cannot be said about soft starters, the capacity of soft starters only represents the maximum starting capacity that it can accept, and the actual output torque depends entirely on the motor itself. Qualitatively speaking, the soft starter is only a power supply, not a drive organization, and does not supply drive torque. No matter how large the capacity of the soft starter is, the motor capacity is too small and still cannot be started successfully. The demand is that the soft starter, as a step-down starting equipment, will inevitably reduce the starting torque and cannot reach the additional torque, which is determined by the principle of the motor, and has nothing to do with the soft start brand and its own control function. Generally speaking, for loads with torque less than 60%, soft starters should be used, and for loads with soft starting torque greater than 60%, other starting equipment should be used.

The third concept of fault: a certain starting method is particularly suitable for heavy load starting. It should be said that the ability to act as a "heavy load" has nothing to do with the soft-start method. "Heavy load" requires the motor to produce a large starting torque at low speed, so it is necessary to be able to make the stator windings of the motor flow a large enough current, which has nothing to do with the choice of soft starting method. If the current of the motor is not large enough, the soft start will be unsuccessful, no matter what soft start method is chosen. On the contrary, as long as the current is large enough, after other control methods, after giving it a better shape of the reference input time curve, it can also achieve successful starting, and has better starting characteristics.

The fourth fault concept: the smaller the starting current, the lower the voltage drop in the grid, the better the function of the starter. This question is in practice the same thing as the second one. The size of the starting current of the motor depends on the load, and the starting current of the motor must be greater than the motor current determined by the driving torque of the load demand in order to start successfully. Under the premise that the power grid condition remains unchanged, the size of the power grid voltage drop completely depends on the size of the starting current of the motor. It can be seen that the above two indicators have nothing to do with the soft starter itself.

Using a soft starter to misconception - Delixi

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