During field commissioning of frequency converter, the following items shall be noted:
(1) Pay attention to the setting of the output frequency range
The setting of the output frequency range of the frequency converter is the upper and lower limit value of the output frequency of the frequency converter. The purpose of setting is 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 the mechanical equipment. This setting is generally set by the maximum speed or experience value of the controlled motor.
(2) Pay attention to the setting of acceleration time
Acceleration time refers to the time required for the output frequency to rise from zero to the maximum frequency, while deceleration time refers to the time required for the output frequency to fall from the maximum frequency to zero. The acceleration and deceleration time is usually determined by the rise and fall of frequency setting signal. Limit the rise rate given by the frequency when the motor accelerates to prevent over-current, and set the fall rate to prevent over-voltage when the motor decelerates. During the acceleration time setting, the acceleration current shall be limited below the over-current capacity of the frequency converter to prevent the over-current tripping of the frequency converter. During the deceleration time setting, the voltage of the smooth circuit shall be prevented from being too large to prevent the frequency converter from tripping due to the regeneration over-voltage stall. The acceleration and deceleration time can be calculated according to the load, but it is rather complicated. The simple method is: according to the load size, set a long acceleration and deceleration time according to experience, and then gradually shorten the set time by observing whether there is over-current and over-voltage alarm through operation. Repeat the operation to determine the best value based on the principle of no alarm during operation.
(3) Pay attention to the setting of motor protection function
In practical engineering, the rated current of the motor shall be taken as the setting value, which is the reference value of motor overload. However, it should be noted that this function setting is invalid when multiple motors are controlled by one frequency converter.
(4) Pay attention to the selection of IGBT associated fast fuse
IGBT is the most important device in the frequency converter。 It is a high-power field-effect composite transistor。 The manufacturer uses a semiconductor fast fuse to protect it, and its fusing time is less than the breakdown time of IGBT。 If its performance changes, IGBT will burn down, so it is very important to select the type of fast fuse。
(5) Pay attention to the setting of fault automatic reset times and reset time
This setting is very important。 In actual operation, it is inevitable that there will be some occasional faults, but they can be overcome automatically in an instant, which can ensure the smooth operation of the frequency converter without finding the fault point。