Frequency converter auxiliary control circuit failure - Solutions - Huaqiang Electronic Network

Control circuits such as inverter drive circuit, protection signal detection and processing circuit, pulse generation and signal processing circuit are called auxiliary circuits. After the auxiliary circuit fails, the cause of the fault is more complicated. Except for the loss of the curing program or the damage of the integrated block (such fault handling methods can only be replaced by the control board or the block replacement), other faults are easier to judge and deal with.

(1) Drive circuit The fault drive circuit is used to drive the inverter IGTR and is also prone to failure. Generally, there are obvious signs of damage, such as abnormal phenomena such as bursting, discoloration, and disconnection of devices (capacitors, resistors, triodes, and printed boards), but there is no damage to the drive circuit. The processing method is generally based on the schematic diagram, each group of driving circuits is inversely checked, measured, replaced, compared, etc. step by step; or compared with another genuine (new) driver board, and the fault point is searched step by step. Troubleshooting steps: First, the entire circuit board is cleaned and decontaminated. If the printed circuit is found to be broken, the line is processed; if the damaged device is detected, it is replaced; according to the author's practical experience analysis, the suspected components are measured, compared, replaced, etc., and some devices need to be measured offline. After the drive circuit is repaired, the oscilloscope should also be used to observe the output waveform of each group of drive circuit signals. If the three-phase pulse size and phase are not equal, the drive circuit still has an abnormality (the replacement component parameters do not match, and this type of Phenomenon) should be checked and processed repeatedly. Damage to the drive circuit in which the high power transistor operates is also one of the causes of the overcurrent protection function. The most common phenomenon that the drive circuit is damaged is the lack of phase, or the three-phase output voltage is not equal, and the three-phase current is unbalanced. (2) Switching power supply damage A more obvious feature of switching power supply damage is that there is no display after the inverter is powered. For example, Fuji G5S inverter adopts two-stage switching power supply. The principle is that the DC voltage of the main DC circuit is reduced from 500V to 300V, and then the voltage is reduced by the first-level switch, and the power output is 5V, 24V and other multi-channel power supply. Switching power supply damage is common with switch tube breakdown, pulse transformer burnout, and secondary output rectifier diode damage. Filter capacitors are used for too long, resulting in changes in capacitance characteristics (capacity reduction or leakage current), and reduced voltage regulation capability. It is also easy to cause damage to the switching power supply. Fuji G9S uses a waveform-generating chip dedicated to switching power supplies. Due to the high voltage of the main circuit, it often causes damage to the chip. Since this chip market is rarely available, the damage is more difficult to repair. In addition, there is no display after the inverter is powered on, which is also one of the more common fault phenomena. The cause of such faults is mostly caused by the damage of the switching power supply. For example, the switching power supply of MF series inverter adopts the more common flyback switching power supply control mode. The short circuit of the output stage circuit of the switching power supply will also cause the switching power supply to be damaged, resulting in no display of the inverter. (3) Feedback, detection circuit failure In the process of using the inverter, it often encounters no output phenomenon of the inverter. Damage to the drive circuit and damage to the inverter module may cause the inverter to have no output. In addition, failure of the output feedback circuit can cause such a malfunction. Sometimes in the actual encounter the inverter has an output frequency, no output voltage (the actual output voltage is very small, can be considered no output), then you should consider whether the feedback circuit is faulty. The feedback resistor used for bucking in the feedback circuit is one of the components that are more prone to failure; the damage of the detection circuit also causes the inverter to display the OC (+pA or +pd or +pn) protection function, detecting the current. Hall sensors are susceptible to drift due to environmental factors such as temperature and humidity, resulting in OC alarms.