Kaifeng Hengda Motor Co., Ltd.
Address: Kaifeng Economic and Technological Development Zone
Sales Office: 0371-69382277
Mobile phone: 18103712151
Introduction to the main starting methods of three-phase asynchronous motor soft start
A soft starter connected in series between the power supply and the controlled three-phase asynchronous motor is used to control the conduction angle of the internal thyristor, so that the input voltage of the three-phase asynchronous motor gradually rises from zero in a preset function relationship until the end of the start. The full voltage of the three-phase asynchronous motor is a soft start. During the soft start process, the starting torque of the three-phase asynchronous motor gradually increases and the speed also gradually increases. Soft start generally has the following starting methods:
This starting method is the simplest. It does not have current closed-loop control. It only adjusts the thyristor conduction angle to increase it as a function of time. The disadvantage is that, due to the unrestricted current, during the starting process of the three-phase asynchronous motor, sometimes a large inrush current is generated to damage the thyristor, which has a large impact on the power grid, and is rarely used in practice. GB motor .
2. Ramp constant current soft start
This starting method is that in the initial phase of starting a three-phase asynchronous motor, the starting current gradually increases, and when the current reaches a preset value, it remains constant (t2 phase) until the start is completed. During starting, the rate of current change can be adjusted according to the load of the three-phase asynchronous motor. If the current rise rate is large, the starting torque is large and the starting time is short. This starting method is the most widely used starting method, and is especially suitable for starting fans and pumps. GB motor.
3. Step start
Start up, that is, the shortest time to make the starting current quickly reach the set value, that is, step start. By adjusting the setting value of the starting current, a fast starting effect can be achieved. GB motor.
4. Pulse shock start.
In the start-up phase, let the thyristor fall back after being turned on for a period of time with a large current for a short period of time, then linearly rise according to the original set value, and connect to the constant current start. This starting method is less commonly used in general loads, and is suitable for heavy-load starting situations that need to overcome large static friction.