What is the correct way to install and use the soft starter?

The soft starter is an important device that is used to start and control the speed of AC motors. Proper installation and use of the soft starter is crucial to ensure its efficient and safe operation. In this article, we will discuss the correct way to install and use the soft starter, including important safety precautions that must be followed. Additionally, we will explore the different starting methods of the soft starter, such as ramp boost soft start, step start, ramp constant current soft start, pulse shock start, voltage double-slope starting, and current limiting start. By understanding these different starting methods, you will be able to choose the most appropriate one for your specific application.

What is the correct way to install and use the soft starter?

1. The soft starter should be installed indoors according to the enclosure protection level (generally IP20).
2. It should be installed vertically, and a space of more than 200MM should be left above and below the soft starter to facilitate heat dissipation.
3. If a thermal relay is installed in the control cabinet, an isolation board should be used to prevent cold or hot flow from blowing to the thermal relay, so as to avoid affecting the action setting value of the relay. .
5. Usually, it is not necessary to test the phase-to-phase and phase-to-ground insulation resistance of the soft starter with a megohmmeter. If it is necessary to test, the three-phase input and output must be short-circuited first, and all plugs on the control board must be unplugged before proceeding.
6. When the input terminal of the soft starter is powered on, the output terminal will have a high induced voltage when the load is open circuit or phase failure, so it is forbidden to touch the output terminal of the soft starter during installation, debugging, maintenance and use to avoid cause electric shock.
7. If a compensation capacitor is connected to improve the power factor, the capacitor must be connected to the input terminal of the soft starter, not the output terminal, otherwise the soft starter will be damaged.
8. The input terminal and output terminal of the soft starter cannot be reversed, otherwise the soft starter and the motor may be damaged.
9. If the inverter has a bypass contactor, be careful when wiring (connecting the main contacts of the contactor) to avoid short circuit accidents.
10. When measuring the insulation resistance of the motor, the three wires between it and the soft starter must be disconnected before proceeding.

What are the starting methods of the soft starter?

1. Ramp boost soft start
The simplest starting method does not have current closed-loop control, and can only adjust the conduction angle of the thyristor so that it increases as a function of time. Disadvantages: Due to the unlimited current, during the starting process of the motor, sometimes a large inrush current is generated to damage the crystal tube, which has a great impact on the power grid and has less practical application.

2. Step start
Starting the machine means taking the shortest time to make the starting current quickly reach the set value, which is a step start. By adjusting the starting current setting value, the effect of quick start can be achieved.

3. Ramp constant current soft start
This starting method is to gradually increase the starting current at the initial stage of motor starting, and keep it constant when the current reaches a preset value until the starting is completed. This starting method is the most widely used starting method, especially suitable for starting fan and pump loads.

4. Pulse shock start
In the initial stage of starting, let the transistor be turned on with a large current for a period of time in a very short period of time and then fall back, then rise linearly according to the original set value, and then connect to a constant current start. This starting method is rarely used in general loads, and is suitable for starting occasions where heavy loads need to overcome large static friction.

5. Voltage double-slope starting
In the starting process, the output torque of the motor increases with the voltage, and an initial starting voltage US is provided during starting. Us is adjustable according to the load. Adjust U to be greater than the static friction torque of the load. When the output voltage reaches When the speed-up voltage Ur is reached, the motor basically reaches the rated speed. The soft starter automatically detects the speed-up voltage during the starting process. When the motor reaches the rated speed, the output voltage reaches the rated voltage.

6. Current limiting start
Current-limited starting is a soft-starting method in which the starting current of the motor is limited not to exceed a certain set value during the starting process. The output voltage increases rapidly from zero until the output current reaches the preset current limit value lm, and then maintains the output current. 1. Advantages: The starting current is small and can be adjusted as required.