Soft starter starting method

Soft starter is a novel motor control device that integrates motor soft start, soft stop, light load energy saving and multiple protection functions. It is called Soft Starter abroad. The most famous domestic soft starter is the Heping hps2 series soft starter. Its main components are three-phase reverse parallel thyristor and its electronic control circuit connected in series between the power supply and the controlled motor.

The starting modes of soft starters can be divided into the following categories:

1. Timing start mode: Set the start time on the soft starter controller. The soft starter starts working after the preset time, gradually increasing the output voltage and current to start the motor smoothly.

2. Manual starting mode: The soft starter controller is equipped with a manual control button. By pressing the button, the soft starter begins to gradually increase the output voltage and current, so that the motor starts smoothly.

3. Automatic start mode: The soft starter can be set to automatically start when it detects that the motor current rises to a certain level, or the motor load factor reaches a certain value, thereby realizing automatic control of the starting process.

It should be noted that after the soft starter is started, when the motor current reaches the rated current, it will automatically output voltage to the motor, allowing the motor to run directly.

During the entire starting process, the soft starter will gradually increase the voltage and current according to the set acceleration curve to avoid the situation where the motor current and voltage are instantly too high during the starting process, thereby ensuring the normal operation of the equipment and extending the service life of the equipment.

Starting method of soft starter:

1. Slope boost soft start: This starting method is simple and does not have current closed-loop control. It only adjusts the thyristor conduction angle to increase it in a certain functional relationship with time. Its disadvantage is that due to the lack of current limiting, a large impact current may sometimes be generated during the motor starting process, causing damage to the thyristor and having a greater impact on the power grid. It is rarely used in practice.

2. Ramp constant current soft start: This starting method is that the starting current gradually increases in the initial stage of the motor starting. When the current reaches the preset value, it remains constant until the starting is completed. During the starting process, the rate of current rise can be adjusted and set according to the motor load. The larger the current rise rate, the larger the starting torque and the shorter the starting time. This starting method is a widely used starting method, especially suitable for starting fans and pumps.

3. Step start: When the machine is turned on, the starting current quickly reaches the set value in a very short time, which is called step start.

4. Pulse impact starting: At the beginning of starting, let the thyristor conduct with a large current for a very short time, then fall back, and then rise linearly according to the original set value, and connect to constant current starting. This starting method is rarely used in general loads, and is suitable for starting occasions with heavy loads and large static friction. The traditional decompression starting methods of cage motors include Yq starting, auto-coupling decompression starting, reactor starting, etc. These starting methods are all step-down starting, which has obvious disadvantages, that is, secondary impact current appears during the starting process.