In daily work, there are many devices that need to be matched to the inverter system. Form an energy-efficient and accurate closed-loop system. So how big is the load of the motor with a large inverter?
First, the choice of the motor should first be based on the average power and maximum power required for the load to be converted to the motor shaft side to select the power of the motor, and also consider the overload capacity of the motor. First select the motor 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 is greater than the rated current of the motor. But the emergence of extreme conditions must be considered. How to choose the inverter - Xinxiang Hengtong Motor Co., Ltd. Therefore, the inverter also needs to provide a short time overload current. For example, the lifting industry will consider adding one model when selecting the inverter. The frequency converter has an overcurrent curve, which is an inverse time curve that describes the relationship between 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 gear (such as lifting applications, the starting current is much larger), sometimes the small power inverter can still drive high-power motors (such as conveyor belts. The current is very stable) )s reason. 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. 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, 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 a common asynchronous motor is controlled by a frequency converter, it should be noted that:
1. At low frequencies (generally less than 25hz), since the motor uses a coaxial fan, the heat dissipation effect will be poor at low speeds. After the motor is heated, the torque characteristics become soft, resulting in problems such as unstable speed and large current.
2, high frequency (generally greater than 70hz), depending on whether the motor can withstand high speed, such as bearing heat, poor dynamic balance and other issues.
3, the real frequency conversion motor F-class insulation starts, 30° higher than the ordinary motor temperature resistance
To control an ordinary asynchronous motor with a frequency converter depends on the working requirements of the motor. If the motor does not run at low or high frequencies for a long time, it is okay to use inverter control, and this application can be seen everywhere.
