Precautions for on-site commissioning of frequency converter

The matters needing attention for on-site commissioning of the inverter are as follows:

(1) Pay attention to the setting of the output frequency range

The setting of the inverter output frequency range, that is, the upper and lower limit values ​​of the inverter output frequency, is set to prevent the output frequency from being too high or too low due to misoperation or failure of the external frequency setting signal source, so as to prevent damage to mechanical equipment. This setting is generally set based on the maximum speed of the controlled motor or the empirical value.

(2) Pay attention to the setting of acceleration time

The acceleration time is the time required for the output frequency to rise from zero to the maximum frequency, and the deceleration time is the time required for the maximum frequency to fall to zero. The rise and fall of the common frequency setting signal are used to determine the acceleration and deceleration time. When the motor is accelerating, the given frequency rise rate is limited to prevent overcurrent, and the drop rate is set to prevent overvoltage when decelerating. When setting the acceleration time, it is also necessary to limit the acceleration current to below the overcurrent capacity of the inverter to prevent the inverter from tripping due to overcurrent; when setting the deceleration time, it is also necessary to prevent the voltage of the smoothing circuit from being too large to prevent the inverter from tripping due to regenerative overvoltage stall. The acceleration and deceleration time can be calculated according to the load, but it is relatively cumbersome. The simple method is: according to the load size, set a longer acceleration and deceleration time based on experience, and then observe whether there is an overcurrent or overvoltage alarm through operation, and gradually shorten the set time. The principle is that no alarm is issued during operation, and repeat the operation to determine the best value.

(3) Pay attention to the selection of IGBT-related fast fuses

IGBT is the most important device in the inverter. It is a high-power field effect compound tube. The manufacturer uses semiconductor fast fuse to protect it. Its fusing time is shorter than the breakdown time of IGBT. If its performance changes, it will burn out the IGBT, so the selection of fast fuse model is very important.

(4) Pay attention to the setting of motor protection function

In actual projects, the rated current of the motor should be used as the set value, which is the reference value for motor overload. However, it should be noted that this function setting is invalid when one inverter is used to control multiple motors.

(5) Pay attention to the setting of the number of automatic fault resets and the reset time

This setting is very important. In actual operation, some faults are bound to occur occasionally, but they can be automatically overcome in an instant, ensuring the smooth operation of the inverter without having to find the fault point.