First, the choice of the motor should first be based on the average power and maximum power required for the load movement, converted to the motor shaft side (may have reducer, pulley and other speed reducer) to select the power of the motor, but also consider the overload capacity of the motor. The motor manufacturer can provide the torque characteristic curve of the motor, and the motor characteristics will change at different temperatures.
By the way: the order of selection is of course to select the motor first and then select the inverter according to the motor, because the ultimate purpose of the control is not the inverter or the motor, but the mechanical load.
Second, the selection of the inverter should be emphasized that it should be selected according to the current. For general load, the inverter can be selected according to the rated current of the motor, that is, the rated current of the inverter (ie the maximum continuous working current under normal environment) is greater than the rated current of the motor. But the emergence of extreme conditions must be considered. Therefore, the inverter also needs to be able to provide a short-time overload current.
(Note: The motor current is determined by the mechanical load.) The inverter has an overcurrent curve, which is an inverse time curve that describes the relationship between the overload current and time. This is the inverter manufacturer often said that the overload capacity can reach 150% of rated current for 2 seconds, 180% of rated current for 2 seconds, which is actually a curve. Therefore, as long as the current curve of the motor is within the overload current curve of the inverter, it is the correct selection. This is why sometimes the inverter power is greater than the motor power 1 or 2 (such as lifting applications), sometimes small power inverters can still drive high-power motors (such as conveyor belts).
Another must pay attention to: in abnormal environments, such as high altitude, high ambient temperature (such as greater than 50 degrees less than 60 degrees environment), side-by-side installation (some inverters are installed side by side without derating, some are derating, according to frequency conversion In case of design decision, etc., consider the derating of the inverter. Information on this aspect of the inverter manufacturers can provide.
The result is: the rated power of the inverter may be greater than the motor power, or less than the motor power. In fact, the selection of the inverter is also determined according to the mechanical load.
Conclusion: The final basis for the selection of the inverter is that the current curve of the inverter includes the current curve of the mechanical load.
Third, Y-type motor and variable-frequency motor Y-type motor, should be ordinary asynchronous motor (Impression is not sure).
The fundamental function of the inverter is to change the power frequency to change the motor speed. Therefore, in theory, no matter what kind of motor, as long as you can change the frequency to adjust the speed, you can use the inverter.
The variable frequency motor has a special design and is more suitable for frequency conversion. Therefore, there is no independent fan or so-called variable frequency motor.
When the ordinary asynchronous motor is controlled by the inverter, it should be noted that: 1. When the inverter is low frequency (generally less than 25hz), since the motor uses a coaxial fan, the heat dissipation effect will be poor at low speed, and the torque characteristic will become soft after the motor is heated. Unstable speed, high current and other issues.
2, high frequency (generally greater than 50hz), depending on whether the motor can withstand high speed, such as bearing heat, poor dynamic balance and other issues.
3. There are still many problems that I can't think of.
In this way, the inverter controls the ordinary asynchronous motor, depending on the working requirements of the motor. Of course, if the motor does not run at low or high frequencies for a long time, it is no problem to use the inverter control. This kind of application can be seen everywhere.
