Maintenance and Fault Shielding Tips for the Drive Circuit of Senlan Inverter sb40-s11-11kw

Repair a Senlan SB40-s11-11kw frequency converter. Upon inspection, it was found that the output terminals u and p+of the module were damaged due to breakdown. As usual, after removing the damaged module, power on the circuit board separately to check if the drive circuit is abnormal. Power on and trip the ole fault. According to the manual, it is an external alarm signal. After short circuiting the control terminal Thr to cm, the power on display is normal. However, when the run button is pressed, a fl fault code will jump, indicating module failure. The drive board is a relatively large circuit board, There are over twenty integrated blocks on top, right? I don’t know why it’s so complicated. Observing the six optocouplers on the back, it should be returning a fl fault to the CPU. Check that the outputs of the six optocouplers are parallel. So short circuit all the input sides, power on, and start running. Sure enough, there is no fl fault code jumping. But when measuring the voltage on the trigger terminal of the module, I was dumbfounded: why is there no voltage! Take a closer look at the driving power supply of the three arm IGBT tubes on u, v, and w, which is output by the switching power supply on the motherboard at 12V, then oscillated and inverted by NE555. Then, a cylindrical sealed transformer is used to extract the voltage from the secondary three windings and rectify it to form three independent driving power supplies. Measure that all three power supplies are available. Then observe that the three driving signals are output by two pairs of tube push pull, which drives the module, The power supply added to the push-pull tube is also available. However, there is no voltage on the trigger terminal of the module, which not only does not have the conventional static negative pressure, but also does not have the excitation positive voltage during operation. Where did this trigger voltage go? Is it possible that the damage to the module was caused by the loss of this voltage? Is it due to a common problem that all six channels have no voltage? Where can I find this large circuit? And users from other places are in a hurry to use the machine and require it to be repaired immediately! I don’t have time to survey the circuit.

Suddenly, it occurred to me that this large circuit, in addition to processing the six pulse signals sent from the CPU, was probably implementing protection for the module. Six optocouplers were short circuited to return the FL signals to the CPU. Although the CPU believed that the module was no longer faulty and sent the six pulses normally, the large protection circuit on the input side of the optocoupler detected an abnormally large “IGBT conduction voltage drop” during the arrival of the six pulses due to the removal of the module, And it was determined that the module was damaged. While sending this fault signal back to the CPU through the six optocouplers, a protective action was also taken. The signal on the module trigger terminal was cut off! It is necessary to artificially create a false image of IGBT tube conduction, deceive the conscientious protection circuit, and release its protection state, in order to check whether the driving circuit can output six qualified excitation pulses, and then determine whether a new module can be replaced for repair
How clever, clever, quick witted! Following this approach, (as the circuit board is powered on separately, the voltage of the 550V DC circuit introduced by p+and n – has been disconnected from the driving circuit. In fact, the purpose of introducing these two terminals into the driving circuit is to form a triggering circuit for the u, v, and w lower three arm IGBT tubes, and to detect the voltage drop of the six IGBT tubes during conduction. In case of abnormalities, the circuit will be protected to protect the safety of the module.) Connect the upper three channels of the triggering terminal with the three terminals that are directly connected to u, v, and w, Connect the n-point, which means that the tubes of the lower three arms were artificially short circuited. At the same time, the short circuiting of the corresponding three optocouplers (those reporting fl faults) was released. After powering on, and starting operation, the fl fault was indeed no longer reported. The triggering terminal of the lower three arms of the measurement module had a positive pulse voltage output. The DC voltage was 4V and the AC voltage was 15V, normal! Follow this procedure again, connect the upper three circuits of the trigger terminal with the three terminals that are directly connected to u, v, and w, and connect them to point p+. That is, artificially short circuit the pipes of the upper three arms. After powering on, start the operation, and measure the trigger terminals of the upper three arms of the module, which also have normal pulse voltage output. This indicates that the entire drive circuit and operation control are normal, and the module can be replaced and repaired

The frequency converter has no cut-off negative pressure. In the shutdown state, the triggering terminal voltage is zero
After replacing the module, the machine is repaired
Ideas determine the way out