There are many types of soft initiators, and the soft initiators selected are not the same according to different site conditions and equipment. So how to carry out the selection of #softstarter?
Bypass type: when the motor reaches the rated revolution, the bypass contactor is used to replace the #softstarter which has completed the task, so as to reduce the heat loss of the thyristor and improve its working efficiency. You can also use a soft starter to start more than one motor.
Bypass type: the thyristor is in the full conduction state, the motor works in the full voltage mode, ignoring the voltage harmonic component, often used for short-time repetitive work of the motor.
Energy saving: when the motor load is light, the soft starter automatically reduces the voltage applied to the motor starter, reduces the current excitation component of the motor, and improves the motor power factor.
There are many types of soft starters, and the #softstarters selected according to different site conditions and equipment are also different. So how to choose the soft starter?
First select according to the motor nameplate parameters. First understand the motor model, rated voltage, rated power, rated stator current, rated rotor current, torque, frequency of use, etc. Fully understand the load situation. If it is a light load, you can choose the standard configuration. Mechanical loads such as belt conveyors, ball mills, brick machines, crushers, etc. are all heavy loads. In this case, increasing the capacity of the #softstarter can improve the service life of the product. In the long run, it will reduce maintenance costs. Then look at the quality of the grid.
Due to different working principles, some soft starters have a large starting current when they are working. If the grid voltage is low, only those with a small starting current, such as magnetic control soft starters and variable frequency starters, can be selected. In addition, the quality of power grid power supply and whether the inverter and reactive power compensation device are running in parallel will cause abnormal operation or even damage of the soft starter. Attention should be paid to the design and selection of layout. Next, pay attention to the number of starts. Some operating conditions may require the motor to be started frequently. Then a variable resistance starter, such as a water resistance cabinet that can only start 3 to 5 times in a short time, cannot be selected. If the load is larger or the start-stop frequency increases, a product with a larger rating must be selected.
Finally, fully consider the specific working conditions. The objective factors of the operating environment of the soft starter, such as humidity, temperature, altitude, dust, etc., will affect the capacity of the equipment. For example, in high-altitude areas, it is necessary to increase the capacity of the soft starter. Factors such as strong ultraviolet rays in the plateau area and large temperature difference between day and night will cause the electronic components to age in advance. Therefore, it is also necessary to increase the capacity usage.
The #softstarter has the advantages of small size, adjustable torque, stable start, small impact and soft stop function. #Softstarter has gradually replaced the traditional step-down starting method of asynchronous motor. So what should you pay attention to when choosing a low-voltage soft starter?
1. Selection of overload protection device
Thermal overload relay with overload protection, phase break protection and temperature compensation function shall be selected for the overload protection device of soft start device. Specific selection, to make the working current of the motor within the range of setting current of the thermal element. The rated current value of the motor should be close to the lower limit of the setting current range of the thermal element for equipment that is prone to overload when working.
- 2.Electrical wiring and component arrangement of low-voltage soft starter cabinet
Electrical wiring of low-voltage soft starter cabinet is shown in Figure 2. The electrical components in the cabinet are arranged in the order shown in the diagram, so that the main wiring is short and not crossed, which is convenient for copper bar connection. The soft starter is installed on the right side of the contactor and is not affected by the heating of other components. The distance between the soft starter and the side wall of the control cabinet and other components must be 2100mm to facilitate the heat dissipation of the soft starter
3.Selection of bypass contactor
At the end of #softstart, the motor has been running on the rated voltage, so the ac contactor can meet the requirements according to the rated current of the motor. It should be noted that when wiring the cabinet, the soft starter and the contactor should be connected in the same phase, and not be connected with the wrong phase sequence.
4.Selection of isolator and fuse
The isolator in the soft starter cabinet can choose the isolator switch or the plastic case circuit breaker with isolation function. Small power soft start cabinet should choose the isolation switch fuse combination of knife melt switch. It not only plays an isolation and protection role, but also can reduce the project cost. When the rated current of the disconnecting switch is greater than the rated current of the motor, it can meet the operation requirements.
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