VSD Failure

[Dairyspark]

Hi everyone

Fitted some big agricultural fans this week and one of the guys when back to adjust the louvres to direct the air. Both fans are controlled by VSD’s and one controller, instead of turning them off at the controller he just switch them off whilst running, which to me is always a bad idea…anyway…the vsd’s are now dead, breaker trips as soon as you try and start the fans.

This has happened a couple of times before on other pieces of equipment running of different types of VSD’s where they’ve been running and then turned off at the isolator or breaker and then they’re just dead.

Why does this happen and will the same thing occur during a power cut?

Thanks

 

[Marvo]

20 years ago power fail regularly damaged VFD's, nowadays nearly all drives are designed to survive a complete unexpected power outage. Usually somewhere in the 600 page, 14 language manual it will state a limit to the frequency of power outages the drive is capable of handing and where I am we have an unstable power grid with planned and scheduled 'loadshedding' several times a day so we need to be mindful of this when specifying VFD's. I recently installed a Danfoss drive that was rated to handle 'occasional' complete power outages and they didnt define exactly what occasional meant. Another drive I recently installed was a small Yasakawa (maybe 18kw) and it was rated to withstand no more than 1 power failure per hour.

Far more likely to cause failure would be rapid cycling of power supply either where the isolation isn't fast and clean or where isolation was followed closely by reapplication of power. Also I'd check for the usual suspects for drive failure such as poor wiring terminations.

I'd be interested to know what the suppliers find when you hand it in for warranty claim.

 

[Dairyspark]

Spoke to the fan supplier today and they’re coming out Monday to find out what’s happened. I’ll see if there’s any info in said 14 language manual I wouldn’t like to think that they were switched off and on several times but it might have been.

Our other guy who turned them off has been told now to shut them down properly in future

 

[Andy™]

maybe better labels / warnings on the isolators that they are for emergency / isolation only

 

[Marvo]

Did your suppliers have any definative answers on why the drive went tits up?

 

[Dairyspark]

Did your suppliers have any definative answers on why the drive went tits up?

Sadly not, so I ended up at the job and learned that the drives were in built to the motors which I’d never seen before. The motor/drives were sat on a pallet and the guy came a few days later to collect. I’ll see if I can find out anything as it would be good to know

 

[Marvo]

Probably EC motors I'm guessing. It's the way it's going nowadays with electronically commutated motors built into the fan blade hub. All in the name of efficiency but they're basically disposable, you can't separate the motor so even if just a bearing fails the entire fan unit is trash.


It's what I call the LED principal where you achieve a gain in efficiency but you end up with land-fill dumps full of items that lasted a quarter of the lifespan they used to and there's no ability to repair or replace components.

 

[binky]

Probably EC motors I'm guessing. It's the way it's going nowadays with electronically commutated motors built into the fan blade hub. All in the name of efficiency but they're basically disposable, you can't separate the motor so even if just a bearing fails the entire fan unit is trash.


It's what I call the LED principal where you achieve a gain in efficiency but you end up with land-fill dumps full of items that lasted a quarter of the lifespan they used to and there's no ability to repair or replace components.

A lot of Leds certainly don't seem to have the lifespan they should have, yet some of the ones I have are over 12years old. I'm of the opinion voltage spikes on the mains are to blame, but have no proof of that.

 

[Geoff1946]

A lot of Leds certainly don't seem to have the lifespan they should have, yet some of the ones I have are over 12years old. I'm of the opinion voltage spikes on the mains are to blame, but have no proof of that.

I don't believe it's the LED chips that are unreliable. The supporting electronics are under-rated and over stressed, just as the CFLs of a couple of decades ago were.
Many have a bridge rectifier on the input which is vulnerable to voltage spikes, or a capacitor dropper which is also in line of fire of any spikes.
I also have suspicions that some imported lamps are designed with 220 volts in mind. Our declared 230 volt standard is misleading when most areas regularly see 240 volts resulting in equipment being operated at he high end of its capability.

 

[Dairyspark]

I don't believe it's the LED chips that are unreliable. The supporting electronics are under-rated and over stressed, just as the CFLs of a couple of decades ago were.
Many have a bridge rectifier on the input which is vulnerable to voltage spikes, or a capacitor dropper which is also in line of fire of any spikes.
I also have suspicions that some imported lamps are designed with 220 volts in mind. Our declared 230 volt standard is misleading when most areas regularly see 240 volts resulting in equipment being operated at he high end of its capability.

We had this issue before, customer was convinced she had a wiring problem in her upstairs lighting, couldn’t find anything wrong but her LED lamps were failing after a day, or flickering off and on. Tested the voltage, 248V (Farm fed off its own pole mounted transformer). Checked the lamps that were working in the other upstairs bedrooms and they were rated 250V and the failing ones were rated 220-230V

 

[Marvo]

There's no reason LED lamps shouldn't be 'universal voltage' ie 100v-250v and there's no reason they shouldn't have built in surge protection or be designed in such a way as to mitigate surges. There's no reason for lots of things in fact, there's no reason for them to have shyte power factor, there's no reason an LED lamp shouldn't last 5 years or considerably more in most applications...christ I've got CFL lamps still in my house that are over 10 years old yet most of the LED lamps I now have to replace them with have about a year life expectancy. There should be legislation demanding the performance of LED lamps because unfortunately the bunch of halfwit money-grabbing tossers otherwise known as the importers and the wholesalers can't be relied on to give a flying frigaroo about quality and the poor tradesman having to bear the brunt of the expense when the rebranded, far east tat they sell doesn't even make it out of warranty period. Unfortunately the wholesaler and the importer is only on the hook for a replacement item which is usually a fraction of what it costs the installer to return to site...probably once to diagnose the faulty unit and again to replace the damn thing with something equally as shyte. I think it's about time the supply chain became liable for all those costs as well and if that were the case I guarantee you they won't be selling half the unfit for purpose, landfill destined garbage that's on their shelves at the moment.

Most of the early lamp failures I've encountered are due to to poor design, corner cutting to save costs and LED COB chips being driven so hard and hot it can only be down to built-in obselesance.

 

[binky]

UK grid voltages can be 253V by law, and if you have solar, the inverter can push upto around 260V under those conditions. So good LEDs need to be rated for 260V