1. The rated current of the inverter is low

As mentioned above, when the rated current of some inverters is less than the rated current of motors of the same capacity, a larger inverter should be selected according to the load of the motor.

2. The motor may be overloaded for a short time

Because the so-called "short time" of the motor is relative to the heating time constant. At least a few minutes, as many as tens of minutes. The overload capacity of the inverter is usually 150% for 1 min. Compared with the electric motor, it has no overload capacity. Therefore, if the motor may be overloaded within the time of the think tank, the capacity of the frequency converter should be increased.

3. Those who have special requirements for acceleration and deceleration time

The length of the motor acceleration time is a relative concept related to the inertia. For example, the acceleration time is 5s, which may be too short for a load with large inertia (large GD2); but it may be too long for a load with small inertia (small GD2).

Generally speaking, for loads that need to be started and stopped under heavy load, the capacity of the inverter should be increased in the following situations:

(1) Those who are required to be able to start and stop quickly;

(2) Frequent jogs.

4. Those with impact load

For example, the motor and the load are connected through a clutch. Usually when the motor is already rotating, the load also rotates due to the coupling of the clutch. Obviously, at the moment the clutch is just engaged, the speed of the motor will decrease, the slip will increase, and the current will increase, which may cause the overcurrent protection to operate. In view of this situation, the capacity of the inverter should be increased