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Selection of inverter capacity

Oct 24, 2020

Selection of inverter capacity

The selection of the inverter capacity is an important and complex issue. It is necessary to consider the matching of the inverter capacity and the motor capacity. A small capacity will affect the effective torque output of the motor, affect the normal operation of the system, and even damage the device, while a large capacity The harmonic components of the current will increase, which also increases equipment investment.

     1. Three steps of inverter capacity selection

     (1) Understand the nature of the load and the law of change, calculate the size of the load current or make a load current diagram I=f(t);

     (2) Pre-select the inverter capacity;

     (3) Check the pre-selected inverter, and check the overload capacity and starting capacity when necessary. If all pass, the pre-selected inverter capacity is selected; otherwise, start from (2) again until it passes.

     On the premise of meeting the requirements of production machinery, the smaller the inverter capacity, the more economical it is.

     2. Selection of inverter capacity based on different motor load current

     (1) There are three ways to express the capacity of the inverter

     Generally speaking, there are three ways to express the capacity of the inverter:

     ●Rated current;

     ●The rated power of the adapted motor;

     ●Rated apparent power.

     (2) Overload capacity of the inverter

     Regardless of the method of expression, in the final analysis, the choice of the rated current of the inverter should be determined according to the actual situation according to the current that the motor may absorb to the inverter. Generally, there are two types of inverter overload capacity:

     ●1.2 times the rated current, lasting 1min;

     ●1.5 times the rated current, lasting 1min.

     Moreover, the allowable current of the inverter has an inverse time relationship with the process time. For example, the rated current of 1.2 (1.5) times can last for 1 min; and the rated current of 1.8 (2.0) times can last for 0.5 min. This means that the duration of the allowable overload current provided to the motor at any time must be within a limited range; the overload capacity index, for the motor, is meaningful only during the start (acceleration) process, and it is running In the process, it is actually equivalent to not allowing overload.