Frequency drives

No, but if stored for a long time UN-powered, the capacitors can degrade and blow on re-energization.

But any piece of electronics, if left connected (load or no load) for a long time is subject to the normal ravages of electrical grids such as spikes that happen as a natural consequences of modern life; grid switches, utility line capacitors coming on and off, distant lightning strikes etc. Line reactors can provide some benefit in avoiding some of these things but without them, it's entirely possible for a VFD to become damaged to the point of causing fuses to blow.

Many VFDs had a design life of 5 to 10 years mtbf for the electrolytic caps.

I am expecting a whole raft of VFDs failures in the near future. Built in obsolescence!

Correct replys

It is indeed a DC bus capacitor "Dry out" as we call it in our jargon.

There are two remedies avaiable.

for this particuoar drive, replace the capacitors. if drive is under 10HP it is not worth it. If over, maybe, check your cost.

For future, we tipically use a 3 phase variac to gradually (very slow) power the dc bus in no load conditions up to the max voltage allowed for this VFD. Than remove it and rewire to normal fused grid.

semi conductor fuse is recommended on the DC bus before the 6pack transisitors. not all VFD has it installed.

Have a nice day

Joe