Analysis: Reasons for Damage of Inverter's Inverter Output Module

Damage to the module caused by a defective circuit in the inverter itself:

1, caused by the poor drive circuit will cause a class of damage to the module

It can be seen from the power supply mode of the drive circuit that it is generally powered by two positive and negative power supplies. The +15V voltage provides the excitation voltage of the IGBT tube to make it turn on. -5V provides the cut-off voltage of the IGBT tube, making it reliable and fast cut-off. When the +15V voltage is insufficient or missing, the corresponding IGBT tube cannot be turned on. If the module failure detection circuit of the drive circuit can also detect the IGBT tube, the inverter can be used to report the OC signal when the signal is put into operation. Inverter protection shutdown action, almost no harm to the module.

And if the -5V cut-off negative pressure is insufficient or is lost (like the three-phase rectifier bridge, we can first think of the inverter output circuit as an inverter bridge, then the IGBT tube is composed of three upper arms and three lower arms. Bridge arms, such as U-phase upper arms and U-phase lower-arm IGBT tubes. When the upper (lower) arm of any phase is energized and turned on, the corresponding lower (upper) arm IGBT tube is When the negative pressure is lost, the collector-gate capacitance of the IGBT tube charges the gate-to-emitter capacitance, causing the tube to be turned on. The two tubes share a short circuit to the DC power supply. The consequence is that the modules are all blown up. !

The loss of the negative voltage, one of which is caused by the damage of the driver IC, may be caused by the damage to the lower tube of the driver stage of the driver IC (usually composed of two stages of complementary voltage follower power amplifiers); Bad; then the negative power supply branch of the driver circuit or the power filter capacitor fails. Once one of the above phenomena occurs, it will certainly be a fatal blow to the module! It is irretrievable.

Bad pulse transmission path will also pose a threat to the module

The 6 PWM inverter pulses output by the CPU are often subjected to six inverting (non-inverting) snubbers and then sent to the input pins of the driver IC. The CPU then drives the IC and then to the trigger terminal of the inverter module. All the way down -

(1) The inverter may report an OC fault. In the lower three-arm IGBT of the inverter bridge, the pressure drop of the pipe during the conduction is detected and processed by the module fault detection circuit, while the IGBT of the upper third leg has a pressure drop detection in a small part of the inverter. In most frequency converters, the pressure drop detection circuit is omitted. When the IGBT tube with the missing excitation pulse happens to be a tube voltage drop detection circuit, the detection circuit will report an OC fault and the inverter will be shutdown after the excitation pulse is lost.

(2) The inverter may run in a wrong phase. The IGBT tube with the missing excitation pulse is the tube without the pressure drop detection circuit. Only the negative pressure exists, which can make it cut off reliably. The phase leg of the phase leg only has half wave output, which causes the inverter to operate in an off-phase mode. The consequence is that a direct current component is generated in the motor winding, and a large inrush current is also formed, resulting in damage to the module due to impact. However, the probability of damage is higher than that of the inverter. An original reason is low.

If this way the pulse transmission path has been broken, even if the module failure circuit can not play a role, but the transformer current detection circuit can play a role, but also can play a protective role, but afraid of this transmission path due to poor contact Such as the cause of failure, when the time-off, and even a random phenomenon of breaking, the current detection circuit is inexplicably, too late to respond, but the inverter caused by "discontinuous polarization" output, the formation of a larger inrush current damage to the module. Content from the Electrical Automation Technology Network

The motor will "joggle" in this output state, and it will produce a "creaky" sound. The heat and loss will be greatly increased, and it will be easily damaged.

3, current detection circuit and module temperature detection circuit failure or failure, the module does not achieve effective over-current and thermal protection, resulting in damage to the module.

4. After the capacity of the main DC circuit's energy storage capacity is reduced or dis- abled, the pulsating component of the DC circuit voltage increases. After the inverter is started, it is not obvious in no-load and no-load fashion, but in the process of loading and starting, the circuit The surge of voltage surges, and the inverter module bursts and damages, and the protection circuit is also indifferent to this.

For inverters that have been operating for many years, after the module is damaged, the inspection of the capacity of the DC storage capacitor can not be ignored. Capacitance's complete inconsistency is rarely encountered, but once it is bumped, it will cause damage to the inverter module during the start-up process with the load, which is also certain!