1. The first-level hazard caused by the bad drive circuit is caused by the power supply mode of the drive circuit. Generally, it is powered by two positive and negative power supplies. The +15V voltage provides the excitation voltage of the IGBT tube to turn it on. The -5V provides the cut-off voltage of the IGBT tube for a reliable and fast cutoff. When the +15V voltage is insufficient or lost, the corresponding IGBT tube cannot be turned on. If the module fault detection circuit of the drive circuit can also detect the IGBT tube, the OC signal can be reported by the module fault detection circuit when the inverter inputs the operation signal. The inverter implements a protection shutdown action, which is almost harmless to the module.
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In case the -5V cut-off negative pressure is insufficient or lost (like the three-phase rectifier bridge, we can first regard the inverter output circuit as an inverter bridge, then the IGBT tube consists of three upper arms and three lower The bridge arm, such as the U-phase upper arm and the U-phase lower arm IGBT tube.), when the upper (lower) bridge arm of any phase is energized and turned on, the corresponding lower (upper) bridge arm IGBT tube is The loss of the negative voltage is formed, and the collector-gate junction capacitance of the IGBT tube is charged to the gate-emitter capacitance, which causes the tube to be mis-conducted. The two tubes are commonly short-circuited to the DC power supply! The consequence is that the modules are flying!
The loss of the cut-off negative voltage is caused by the damage of the driver IC; it may also be caused by the damage of the lower tube of the power boost stage of the driver IC (usually composed of two-stage complementary voltage follower power amplifier); the trigger terminal lead connection Bad; then the negative power supply branch of the drive circuit or the power supply filter capacitor fails. Once one of the above phenomena occurs, it will definitely form a fatal blow to the module! It is irreparable.
2, the pulse transmission path is not good, it will also form a 6-channel PWM inverter pulse that is threatened by the CPU. It is often sent through the six-inverting (in-phase) buffer, and then sent to the input pin of the driver IC, from the CPU to the driver IC. To the trigger terminal of the inverter module, as long as there is one interrupt in the 6 signals (1), the inverter may report an OC fault. The lower three-arm IGBT tube of the inverter bridge is tested and processed by the module fault detection circuit, and the IGBT tube of the upper three bridge arm has a tube voltage drop detection in a small part of the inverter. In most inverters, the tube voltage drop detection circuit is omitted. When the IGBT tube with the excitation pulse is lost, it happens to have the tube voltage drop detection circuit, after the excitation pulse is lost, the detection circuit will report the OC fault, and the inverter stops the protection;
(2) The inverter may run out of phase. The IGBT tube that loses the excitation pulse is the tube without the tube voltage drop detection circuit, and only the cut-off negative pressure exists, which can make it reliably cut off. The phase bridge arm only has a half-wave output, which causes the inverter to run out of phase. The consequence is that a DC component is generated in the motor winding, and a large inrush current is also formed, thereby causing damage to the module and being damaged! However, the probability of damage is lower than that of the first one.
If the pulse transmission path of this circuit is always broken, even if the module failure circuit can not function, the current detection circuit such as the transformer can play a role and can also play a protective role, but it is feared that the transmission path is poorly contacted. When the cause of the fault occurs, the time is interrupted, and even the random breaking phenomenon occurs. The current detecting circuit is inexplicable, so there is no time to react, and the inverter causes the "discontinuous phase-off" output to form a large inrush current and damage the module.
In this output state, the motor will “bounce†and make a “squeaky†sound. The heat and loss will increase greatly and it will be easily damaged.
3. The current detection circuit and the module temperature detection circuit fail or fail, and the module does not effectively protect against overcurrent and overheating, thus causing damage to the module.
4. After the capacity of the storage capacitor of the main DC circuit decreases or loses capacity, the ripple component of the DC link voltage increases. After the inverter is started, the no-load and no-load fashion is not obvious, but during the load start process, the loop The voltage surges, the inverter module bursts and damages, and the protection circuit is also at a loss.
For inverters that have been running for many years, after the module is damaged, the storage capacitor capacity of the DC circuit cannot be ignored. The complete loss of capacitance is rarely encountered, but once it is hit, it will cause damage to the inverter module during the load start process, which is also certain!