How to solve the problem of inverter capacity

    Match the power and load of the motor. The capacity of the inverter with the same capacity to drive the motor varies with the nature of the load carried by the motor, and the capacity of the inverter required by the motor with the same power varies with the nature of the load. The capacity of frequency converter required by square torque load (fan) is lower than that of constant torque load. Generally, the frequency converter has directly given the rated power or its apparent power suitable for driving the motor. In the chemical industry, for square torque loads such as fans and pumps, the corresponding frequency converter can be selected according to the motor power. In the following cases, the capacity of frequency converter must be increased:

    ① The motor starts the load with large mechanical inertia in a short time;

    ② The motor is required to accelerate and decelerate frequently;

    ③ Within the desired acceleration and deceleration time, the maximum current of the motor is greater than the overload capacity of the frequency converter (when it reaches 1.5 times of the rated current within 1 min). Under the above circumstances, the frequency converter cannot be simply selected according to the motor power.

    The motor with light load cannot be equipped with small capacity inverter at will. The motor pulls the trolley with a large horse, and the power output is insufficient. Although the motor is allowed to be equipped with a frequency converter with a slightly smaller nominal power than the motor, the larger the motor capacity is, the smaller its inductance is, and the pulsating current component caused by harmonics will increase. Therefore, when the load of the asynchronous motor is small and you want to use a frequency converter with smaller capacity, on the one hand, you should consider that the no-load current of the large capacity motor is large, and once loaded, whether the total load current exceeds the rated current of the frequency converter, on the other hand, you must note that the pulsating current will increase.

    Correct selection of inverter V/f graphics. For 50Hz, 380V AC asynchronous motor, appropriate Vif figure shall be selected according to actual needs and allowable working range of motor during actual operation. In the chemical industry, the frequency converter is mainly used for speed regulation of pumps. Therefore, when selecting Vif graphics, the condition that the output frequency and the maximum output frequency are 50Hz when the rated voltage is 380V should be met. The selection of Vif graphics of frequency converter used for speed regulation of pump in our factory is based on the above principles.

    Selection of torque lifting curve. The output torque of the motor can be effectively improved by torque lifting. If the curve is too small, the output torque of the motor will be insufficient and it is difficult to start; If it is too large, the saturation loss of motor magnetic flux will increase accordingly, and the increase of motor temperature rise is not conducive to energy conservation. Therefore, when choosing the torque lifting curve, we should choose it according to the nature of the load.