Publish Time: 2022-08-01 Origin: Site
1. Whether the motor can start successfully is related to the performance of the soft starter
This problem needs to be analyzed in two aspects. First of all, we must see that the quality of products corresponding to good brands is relatively good, so in terms of reliability, the probability of failure of good brands will be relatively small. However, as far as the nature of the starting motor load is concerned, the starting torque of the motor plays a decisive role, and for the motor torque, it is related to many factors. Secondly, as a 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. Changing the stator voltage also changes the motor torque. This basic The principle cannot be changed. All brands of soft starters are designed based on this principle, which has nothing to do with their product performance or quality. Therefore, whether it is a domestic brand or a foreign brand, the starting torque is basically the same. As long as the soft starter is not faulty, if the motor cannot start the load, use another better brand. Product is useless.
2. Whether the motor can start successfully is related to the capacity of the soft starter
This problem actually confuses the capacity of the soft starter with the capacity of the motor, or confuses the capacity with the driving torque, which are actually two different concepts. For the motor, the capacity and the driving torque are of the same nature. The large capacity of the motor also reflects that it can output a larger driving torque. For the soft starter, this is not the case. The capacity of the soft starter only represents the maximum starting capacity that it can withstand. As for the actual output torque, it depends entirely on the motor itself.
Qualitatively speaking, a soft starter is just a power source, not a drive mechanism, and cannot provide drive torque. No matter how large the soft starter capacity is, but the motor capacity is too small, it still cannot start successfully. It should be noted that the soft starter, as a kind of step-down starting equipment, will inevitably reduce the starting torque and fail to reach the rated torque. This is determined by the principle of the motor, and has nothing to do with the soft starter brand and its own control performance. Generally speaking, for loads with torque less than 60%, a soft starter should be used, and for loads with soft starting torque greater than 60%, other starting equipment should be used.
3. A certain starting method is especially suitable for heavy-load starting
This problem actually confuses the capacity of the soft starter with the capacity of the motor, or confuses the capacity with the driving torque, which are actually two different concepts. For the motor, the capacity and the driving torque are of the same nature. The large capacity of the motor also reflects that it can output a larger driving torque. For the soft starter, this is not the case. The capacity of the soft starter only represents the maximum starting capacity that it can withstand. As for the actual output torque, it depends entirely on the motor itself.
Qualitatively speaking, a soft starter is just a power source, not a drive mechanism, and cannot provide drive torque. No matter how large the soft starter capacity is, but the motor capacity is too small, it still cannot start successfully. It should be noted that the soft starter, as a kind of step-down starting equipment, will inevitably reduce the starting torque and fail to reach the rated torque. This is determined by the principle of the motor, and has nothing to do with the soft starter brand and its own control performance. Generally speaking, for loads with torque less than 60%, a soft starter should be used, and for loads with soft starting torque greater than 60%, other starting equipment should be used.
4. The smaller the starting current and the lower the grid voltage drop, the better the performance of the starter
This question is actually the same as the second question. The size of the motor starting current depends entirely on the load. The motor starting current must be greater than the motor current determined by the driving torque required by the load to start successfully. Under the premise that the grid condition remains unchanged, the size of the grid voltage drop depends entirely 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.
There are four types of water pump starting: direct start, step-down start, soft start and variable frequency start. Direct start is generally suitable for low-power motors. We generally only use it on pumps below 15kw, and the price is cheap; step-down start is star-delta conversion start, that is, the start is accelerated twice to reach the rated speed, generally used on pumps above 18.5kw, and the price is moderate; soft start is gradually increased to the rated speed, the impact on the pump is small, the price is relatively high, generally 3 times the step-down start; the most advanced is the variable frequency start. Soft start and variable frequency start have significant effect on energy saving and consumption reduction.
Under the condition that the pump outlet valve is closed, the pump inlet valve is opened, and the pump is "self-priming" (the liquid level is higher than the inlet of the pump), the starting procedure of the pump is: start the motor, and when the motor runs normally, slowly Open the outlet valve to increase the current slowly.
However, in the case of unmanned operation (opening the valve), the pump is automatically started, and the diameter and length of the pipeline are large (the quality of the water in the pipeline will be very large). Accelerate quickly), which will make the motor start-up current very large, causing the motor to trip and damage the machinery and motor. Using soft start (adding a soft starter in the circuit)----that is, the motor slowly increases the speed to overcome the above situation. This kind of soft starter that specially controls the slow speed and speed of the motor is the soft start of the water pump.
When starting directly, the current may reach 6-7 times the rated current, which will cause problems to other electrical equipment in the factory. When using a soft starter, the starting current is about 2-3 times the rated current. For the water pump, there is also a soft stop, which allows the water to slowly fall back and eliminates the water hammer effect. Simply put, it starts slowly and stops slowly. This slow time can be adjusted, about 1-60 seconds.