three phase ac motor start overload

  • How does the three phase ac motor start overload? Home appliances motor company: Yisenbao introduces to you that the stator current at the moment of starting a high-voltage three-phase motor is the starting current, and this starting current is the short-circuit current under the rated voltage, which is 5-7 times the rated current. Such a large starting current will increase the voltage drop on the power supply and the power supply line, causing voltage fluctuations in the power grid, and at the same time affecting the normal operation of other loads connected in parallel on the same power grid. For example, the brightness of the nearby lighting is weakened, the ac motor voltage and speed are reduced in normal operation, and even the ac motor overheating is caused by the stoppage due to the inability to drag the load. The impact on the smaller capacity power supply transformer or the power grid system is particularly severe. . In this case, for the motor itself, although the starting current is large, it does not last for a long time. The temperature rise of the motor will not overheat, and it will not have a destructive effect (frequent starting, large inertia, and long starting time. Except for the motor). However, the influence of electromagnetic torque formed by excessive electromagnetic force on the motor cannot be ignored.

    three phase ac motor

    The high-voltage three-phase ac motor itself has a relatively large current demand, and its starting current is several times the foundation. This huge starting current will increase the voltage drop on the power supply and the power supply line, and the ac motor voltage will increase, resulting in the grid voltage Fluctuations also affect other loads that work together on the grid. A long duration will have a destructive effect on the high-voltage motor, and the electromagnetic torque formed by excessive electromagnetic force is also harmful to the performance of the high-voltage motor.

    The starting current of the high-voltage motor will have a certain performance impact on the equipment. The country has formulated relevant standards for this. For the safe and normal operation of electrical equipment and lines, the high-power engine must be equipped with additional starting equipment that can reduce the starting current.

    Even if the motor starts with no load, its instantaneous starting current will reach 4 to 6 times the rated current of the motor, and the integrated motor protector will delay this period of time for a few seconds, so that it does not trigger the protection circuit action. After a few seconds, the integrated motor protector starts to operate and performs normal protection. Generally, the short-circuit current of the motor is generally set at 8 to 10 times the rated current of the motor. The protective measure taken for 10 times the excess current is to quickly disconnect without delay. Under normal circumstances, the motor is forbidden to start with load, because the no-load starting current is inherently large. If it is started with load, its current will be far Exceeding the starting current range set by the integrated motor protector, ac motor overheating, reaching the short-circuit current range of the motor, the motor starting current will be too large, and the protection will cause the shutdown.

    The above is the analysis of three-phase motor starting overload introduced by Yisenbao Motor. Yisenbao is a well-known Home appliances motor company in the industry. Our products include three phase ac motor, single phase ac motor, household appliances motor, etc. If you are interested, please contact us!


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