Other faults of the inverter

by:Sure     2021-08-11
In addition to the above faults displayed by the inverter fault code, the inverter has some non-display faults. The analysis is as follows for your reference. 3.1 Main circuit tripping This kind of fault is manifested by a loud noise (commonly known as firing) during the operation of the inverter, or failure to power on when the inverter is turned on, and the circuit breaker or air switch used for inverter control has tripped. This situation is generally due to the main circuit (including the above-mentioned faults with the inverter fault code display, the inverter also has some non-display faults, the analysis is as follows for your reference. 3.1 The main circuit trip This fault is manifested as a frequency conversion There is a loud noise (commonly known as 'fire shot') during the operation of the inverter, or the circuit breaker or air switch used for inverter control has tripped. This situation is generally due to the main circuit (including rectifier modules, electrolytic capacitors, etc.). Or the inverter bridge) is directly broken down and short-circuited. At the moment of breakdown, the strong high current causes the module to burst and produce a huge noise. There are many reasons for the damage of the module, and it is not easy to generalize. Now only the author has encountered it. Enumerate several types of situations. (1) The damage of the rectifier module is mostly caused by the pollution of the power grid. Because the controllable rectifier (such as thyristor electric welding machine, locomotive charging bottle, etc.) is used in the control circuit of the inverter, it is all controllable. Rectifier), so that the waveform of the power grid is no longer a regular sine wave, and the rectifier module is damaged by the pollution of the power grid. This needs to enhance the power absorption capacity of the input end of the inverter. This circuit is generally designed inside the inverter. But with As the pollution of the power grid deepens, the circuit should also be continuously improved to enhance the ability to absorb the peak voltage of the power grid. (2) The damage of electrolytic capacitors and IGBTs is mainly caused by uneven voltage, which includes dynamic voltage equalization and static voltage equalization. In the frequency converter that has been used for a long time, due to the reduction of the capacity of some capacitors, the uneven voltage of the entire capacitor group is caused, and the capacitors with high sharing voltage must burst. The damage of the IGBT is mainly due to the excessively high bus spike voltage and the buffer circuit Caused by poor absorption. During the IGBT turn-on and turn-off process, there is a very high current rate of change, namely di/dt, and the voltage applied to the IGBT is: Uu003dL×di/dt, where L is Bus inductance. When the bus inductance is too high due to the unreasonable bus design, the voltage on the module will be too high and breakdown. The instantaneous high current of the breakdown will cause the module to burst. Therefore, reducing the bus inductance is a good way to make the inverter. The key. The wide copper bar structure used in our improved circuit is better. The multi-layer bus bar structure used abroad is worth learning. (3) The parameter setting is unreasonable. Especially under large inertia loads, such as centrifugal fans, centrifugal mixers, etc., due to frequency conversion The frequency drop time of the inverter is too short, causing the motor to generate electricity during the shutdown process, which will cause the bus voltage to rise, which exceeds the limit that the module can withstand and burst. In this case, the drop time should be as long as possible, generally not less than 300s, or in the main circuit Add a bleeder circuit and use an energy dissipation resistor to release the energy. R is the energy dissipation resistance. When the bus voltage is too high, the A tube is turned on to make the bus voltage drop, and then it is turned off after normal. The bus voltage tends to It is stable and ensures the safety of the main device. (4) Of course, there are many reasons for module explosion. For example, the main control chip is disordered, signal interference causes the upper and lower bridge arms to pass through, etc., it is easy to cause the module to explode, and the poor absorption circuit is also the direct cause , Should be treated differently according to the situation, in order to make the inverter better. 3.2 The delay resistor is burned out, which is mainly caused by the problem of the delay control circuit. (1) Delay in the inverter In the time circuit, most of the thyristor (SCR) circuits are used. When it is not conductive or has poor performance, it can cause the delay resistor to burn out. This is mainly caused by the moment of booting. (2) During the operation of the inverter, when there is a problem with the control circuit, some of it is caused by the breakdown of the main circuit module, which causes the voltage of the control circuit to drop, causing the delay SCR control circuit to work abnormally, and the SCR cut-off causes the delay resistor to burn. Bad. There are also problems with the power supply loop of the control transformer, causing the main control board to lose voltage instantly, causing the thyristor to work abnormally and causing the delay resistor to burn out. 3.3 Only frequency but no output This kind of failure is generally in a circuit where the IGBT drive circuit is controlled by a switching power supply. This problem will occur when the switching power supply or the power excitation circuit driven by it fails. In the wind and solar inverter, the switching power supply is generally 30~35V, ±15V or ±12V, and the output of the power excitation is a square wave with an amplitude of ±35V and a frequency of about 7kHz. Detect these voltage values u200bu200band use an oscilloscope to measure the output of the power excitation to be judged, as shown in Figure 12. But after replacing this part of the device, it should be adjusted so that the voltage on the drive board meets the specified value (+15V, -10V). 3.4 There is no display on the panel after power-on This is mainly a fault that often occurs in hoist inverters, so the power supply for the main control board of the inverter is switching power supply. When it is damaged, the main control board will be abnormal and no display. This type of power supply is mostly caused by damage to its internal fuse. Because the switching power supply is greatly impacted at the moment of power transmission, causing the fuse to fuse instantaneously, the problem can be solved by replacing a suitable fuse. In some cases, the varistor inside is damaged, so you can replace it with a new switching power supply. 3.5 The frequency does not rise, that is, the inverter only runs at '2.00' Hz after power-on and does not rise. This is mainly due to the abnormal external control voltage. The external control voltage of the inverter is introduced through the 16-pin terminal of the main control board. If the external control voltage is abnormal or there is a problem with the internal operation of the 16-pin, the fault will be caused. At this time, please check the potential for adjusting the frequency. W2 (3.9K), measure whether there is a voltage of 0-5V on pin 16 and then check whether the C point of the operational amplifier circuit is working normally. If the voltage of pin 16 is normal, but there is no output at point C, it is usually caused by abnormal operating voltage of the op amp. Check whether the power supply voltage is normal or whether the op amp is damaged.
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