2024-05-31
When choosing a soft starter, you often hear about the rated current of the motor and the starting current. What do these two currents mean? Today, the soft starter factory, Axwell, will learn with you.
Rated current refers to the current at which an electrical device operates at rated voltage and rated power. It can also be defined as the current that electrical equipment can operate continuously for a long time under rated environmental conditions (ambient temperature, sunlight, altitude, installation conditions, etc.). The current during normal electrical operation should not exceed its rated current.
Starting current refers to the impulse current of electrical equipment at the beginning of startup, which is the change in current from the moment the motor or inductive load is energized to a brief period of stable operation. This current is generally 4-7 times the rated current. After using a soft starter, the starting current is generally 2-3 times the rated current, which can be estimated at 2.5 times.
The soft starter only assists in the entire motor starting process, reducing the motor starting current and alleviating the impact on the power grid during high-power motor starting.
The Axwell motor soft starter uses three-phase anti parallel thyristors as voltage regulators, which are connected to the stator. This type of circuit, such as a three-phase fully controlled bridge rectifier circuit, uses a soft starter to start the motor. The output voltage of the thyristor gradually increases, and the motor gradually accelerates until the thyristor is fully conductive. The motor operates on the mechanical characteristics of the rated voltage, achieving smooth starting, reducing the starting current, and avoiding overcurrent tripping during starting. When the motor reaches the rated speed, the starting process is completed, and the soft starter automatically replaces the completed thyristor with a bypass to provide the rated voltage for the normal operation of the motor, reducing the thermal loss of the thyristor, extending the service life of the soft starter, improving its work efficiency, and avoiding harmonic pollution in the power grid. The soft starter also provides a soft stop function, which is the opposite of the soft start process. The voltage gradually decreases and the speed gradually drops to zero, avoiding torque impact caused by free parking.
