Analysis and treatment of common fault phenomena of Siemens inverter

1. Features of Siemens general-purpose inverters

Siemens inverters are mainly divided into three categories: general-purpose, engineering and special-purpose. New products are constantly launched to meet the special requirements of different users.

2. Analysis and treatment of common fault phenomena

When we encounter a faulty inverter, before powering on, we must first use a multimeter to check whether the rectifier bridge and IGBT module are burned, and whether there are obvious signs of burning on the circuit board.

The specific method is: use the resistance 1K range of the multimeter (preferably an analog meter), connect the black test rod to the DC terminal (-) of the inverter, and use the red test rod to measure the resistance of the three-phase input terminal and the three-phase output terminal of the inverter. The resistance should be between 5K-10K, the three-phase resistance should be the same, the output resistance should be slightly smaller than the input resistance, and there should be no charging and discharging phenomenon. Then, connect the red test rod to the DC terminal (+) of the inverter, and the black test rod to measure the resistance of the three-phase input terminal and the three-phase output terminal of the inverter. The resistance should be between 5K-10K, the three-phase resistance should be the same, the output resistance should be slightly smaller than the input resistance, and there should be no charging and discharging phenomenon. Otherwise, it means that the module is damaged. At this time, you cannot blindly power on, especially when the rectifier bridge is damaged or there are obvious signs of burning on the circuit board, so as not to cause greater losses.

If the above measurement results indicate that the module is basically fine, you can power it on and observe.

(1) After power-on, the panel displays [F231] or [F002] (MM3 inverter). There are two possible reasons for this fault. The most common one is due to a problem with the power driver board, and a small number of cases are caused by the main control board. You can try replacing the main control board first. Otherwise, the problem must be in the power driver board.

(2) After power-on, there is no display on the panel (MM4 inverter), and the indicator light under the panel [green light is off, yellow light flashes quickly], this phenomenon indicates that the rectifier and switching power supply are basically working normally, and the problem lies in one of the switching power supply circuits (rectifier diode breakdown or open circuit). You can use a multimeter to measure several rectifier diodes of the switching power supply, and it is easy to find the problem. Replace a corresponding rectifier diode and the problem will be solved. This problem is generally caused by the low withstand voltage of the diode and the pulsation impact of the power supply.

(3) Sometimes the display [F0022, F0001, A0501] is uncertain (MM4), and it can be normal when you knock on the case or move the panel and motherboard. This is generally a connector problem. Check the connectors in various parts. It is also found that some machines are caused by quality problems of resistors and capacitors on the circuit board or poor welding.

(4) After power-on, the display shows [-----](MM4), which is usually a problem with the main control board. In most cases, the problem can be solved by replacing the main control board. This is usually caused by strong electrical interference in the peripheral control circuit, which causes damage to certain components of the main control board (such as chip capacitors, resistors, etc.). I analyzed that this is also related to poor heat dissipation of the main control board. However, some individual problems may lie on the power supply board.

(5) The display is normal after power-on, but overcurrent is displayed as soon as it is running. [F0001](MM4)[F002](MM3) Even if it is unloaded, this phenomenon generally indicates that the IGBT module is damaged or there is a problem with the driver board. It is necessary to replace the IGBT module and carefully check the driver part before powering on again. Otherwise, the IGBT module may be damaged again due to the problem of the driver board! This problem usually occurs because the inverter is overloaded multiple times or the power supply voltage fluctuates greatly (especially low), causing the inverter pulsating current to be too large, and the main control board CPU has no time to respond and take protective measures.

There are also some special faults (not common but with some general significance, which can be used as a reference, hoping to achieve the effect of inspiring others), for example:

(1) There is a frequency converter (MM3-30KW) that often stops "for no reason" during use. It may be normal when it is turned on again. After the machine was brought to me, I did not find the problem at first. After a long period of observation, it was found that the main contactor was not normally attracted after power was turned on - sometimes the power would be lost and it would jump randomly. The cause of the fault was found to be due to the leakage of the filter capacitor of the power supply from the switch power supply to the contactor coil, causing the voltage to be low. At this time, if the power supply voltage is high, it is not a big problem. If the power supply voltage is low, it will cause the contactor to be abnormally attracted and cause an unexplained shutdown.

(2) There is another inverter (MM4-22KW). When it is powered on, the display is normal. When the running signal is given, [P----] or [-----] appears. After careful observation, it is found that the fan speed is a bit abnormal. When the fan is unplugged, it will display [F0030]. During the maintenance process, the alarm is sometimes chaotic, and [F0021F0001A0501] and so on have appeared. When I first give the running signal and then connect the fan, [P----] will not appear. However, when a fan is connected, the fan speed is normal, and the output three-phase is also normal. When the second fan is connected, the fan speed is obviously abnormal. So I analyzed that the problem is on the power supply board. It turned out that the power supply filter capacitor from the switching power supply is leaking. The problem was solved by replacing the same capacitor.

(3) There is a 75kW MM440 inverter in a steel plant. After installation, it started to run normally. After more than half an hour, the motor stopped, but the inverter's operating signal was not lost but was still maintained. The panel displayed the alarm message [A0922] (the inverter has no load). The three-phase output terminal of the inverter was measured to have no voltage output. The inverter was manually stopped and ran again and returned to normal. Under normal circumstances, the output current displayed on the panel is 40A-60A. After more than 20 minutes, the same fault phenomenon occurred. At this time, the output current displayed on the panel was only about 0.6A. After analysis, it was determined that there was a problem with the current detection unit on the driver board. The problem was solved after replacing the driver board.

To sum up, the proportion of problems with large components such as IGBT power modules is not high. As I mentioned earlier in the characteristics of Siemens general inverters, the proportion of failures caused by some low-end simple component problems and assembly problems is relatively high. If you have drawings and parts, these problems are not difficult to solve and the cost is not high. Otherwise, it is still not easy to solve these problems. The simplest way is to replace the entire circuit board!