Let's first look at the common faults of Emerson, the mainstream inverter brand in the United States. After repairing nearly 100 inverters of this brand, I found a typical fault phenomenon: after connecting the power, the "POWER" power indicator on the inverter display panel lights up normally, but the display (early BCD seven segment digital tube, and now there is also an LCD display), but everything is gone after it is instantly lit! And in this process, when each function key is pressed, the inverter does not have any response action, just like "crash"!

In response to this situation, some peers tend to overhaul from two aspects: one is that the voltage supplied by the switching power supply to the main control board is abnormal; the other is that the main control board or display panel circuit has problems such as incomplete reset, display driver IC damage, etc.

But after some tossing, the result is often nothing! So what is the reason for the failure phenomenon of Emerson inverter? In this regard, you may wish to remove the power cord of the cooling fan in the inverter from the circuit first - in 95% of cases, after the cooling fan is removed, the inverter will often return to normal! The conclusion is self-evident that the common problem that causes this kind of failure of Emerson inverters is the damage of the cooling fan!

Next, let's take a look at the typical faults of the Danish brand Danfoss inverter that entered my country's industrial control market earlier. After repairing nearly 200 inverters of this brand, I found that "alarm 29" overheating faults often occurred in such inverters!

After comparative analysis of its structure and circuit, I found that Danfoss inverters have two major characteristics in the treatment of heat dissipation measures: First, the inverters of this brand are rarely equipped with heat dissipation backplanes, and their heat dissipation is highly dependent on cooling fans. And the cleanliness requirements for heat dissipation holes and air ducts are also very high (because the quality of the electronic components used is relatively good, so the "fried machine" failure caused by this is very rare)!

The cooling fan control method of the two inverters of this brand is also different from that of most products. It does not have the common "automatic opening" and "always running" modes to choose from, but is measured according to the temperature sensor (thermistor). The temperature value is controlled by PWM to drive the cooling fan to automatically adjust the speed to complete the cooling task.

Referring to the two major features of the Danfoss inverter cooling system above, once the brand inverter reports an overheating fault code, we should clean it first. If the fault remains the same, we should focus on the PWM control circuit of the cooling fan (because the quality of the cooling fan used by this brand of inverter is quite good, at least I have not seen a single case of damage in the actual maintenance work), after all, this is the cause of The common problem of Danfoss inverter reporting "alarm 29" fault code!

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