# how many long vfd can lasts?



## scotch (Oct 17, 2013)

Must have had good capacitors in the build ! But you've probably " jinxs it " now....it'll fail soon !


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## micromind (Aug 11, 2007)

I've seen a few of the old Saftronics VFDs still working. I bet they're 20 years old. 

One of the keys to making a VFD last is to have the power supply clean. Spikes and other garbage (often from other VFDs) will cause trouble with the input diodes and capacitors.

Installing it in a clean cool room goes a long way too.


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## JRaef (Mar 23, 2009)

The power capacitors have an expected life of between 7 and 10 years. That's not to say that they will not last longer, they often do. But after 10 years it's a safer bet that you are on borrowed time. Other than the caps though, 20+ years is not unheard of. A-B stopped making the 1336 drives in 1998 and the components used in them went obsolete about 5 years ago so you can't even fix them any more. But I know people who have dozens of them running their facilities every day.

Manufacturers have a rating system referred to as "Mean Time Between Failures" (MTBF) and most decent quality VFDs come in at about 110,000 hours MTBF, so about 12.5 years if running 24/7/365. But there are plenty of people out there who will tell you that MTBF values are marketing fairy tales...


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## Mike_kilroy (Sep 2, 2016)

I second Jraef's reply. Besides a lot of 1336 drives still in use, we service Kollmorgen drives still in operation from the 1970's.


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## glen1971 (Oct 10, 2012)

JRaef said:


> The power capacitors have an expected life of between 7 and 10 years. That's not to say that they will not last longer, they often do. But after 10 years it's a safer bet that you are on borrowed time. Other than the caps though, 20+ years is not unheard of. A-B stopped making the 1336 drives in 1998 and the components used in them went obsolete about 5 years ago so you can't even fix them any more. But I know people who have dozens of them running their facilities every day.
> 
> Manufacturers have a rating system referred to as "Mean Time Between Failures" (MTBF) and most decent quality VFDs come in at about 110,000 hours MTBF, so about 12.5 years if running 24/7/365. But there are plenty of people out there who will tell you that MTBF values are marketing fairy tales...


There's about a dozen 1336's, 2 - 1557's and a couple of Toshiba Tosverts in the area I'm working in. And they typically run 24/7..


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## JRaef (Mar 23, 2009)

glen1971 said:


> There's about a dozen 1336's, 2 - 1557's and a couple of Toshiba Tosverts in the area I'm working in. And they typically run 24/7..


Those 1557s can't be repaired any more either, someone should think about upgrading, because typically when anything is run by an MV drive, it's important to your livelihood...

I have a refinery client with two of them as well and although they too are still running, the operations people are increasingly nervous. Management won't cut loose of the cash though, they insist on limping along, "just one more year"... for 5 years now. Yet if one of them goes down unexpectedly, the losses and fines will add up to millions in a matter of hours. It's so foolish it hurts.


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## Mike_kilroy (Sep 2, 2016)

JRaef said:


> Those 1557s can't be repaired any more either,


You might temper your replies stating "these cannot be repaired anymore" as may 3rd party repair houses are doing it on daily basis. 

PLC Center for one will repair any 1336 in short order and warranty it for a year... It is not the OEM but some of these places are decent - when they specialize on a brand or two: In my experience, those who say they can repair ANY drive typically do bad job on most.


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## scotch (Oct 17, 2013)

Mike_kilroy said:


> You might temper your replies stating "these cannot be repaired anymore" as may 3rd party repair houses are doing it on daily basis.
> 
> PLC Center for one will repair any 1336 in short order and warranty it for a year... It is not the OEM but some of these places are decent - when they specialize on a brand or two: In my experience, those who say they can repair ANY drive typically do bad job on most.


Myself , I'd just go with "can't be repaired "....I've had the experience of pulling a so called " fixed "drive after a couple of weeks.... I just feel more comfortable with a factory new drive....and I don't have to explain now useless ..."it'll save you money"...repair to the customer . You know how well that goes when it's more downtime now happening . The customer starts to loose faith .


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## JRaef (Mar 23, 2009)

Mike_kilroy said:


> You might temper your replies stating "these cannot be repaired anymore" as may 3rd party repair houses are doing it on daily basis.
> 
> PLC Center for one will repair any 1336 in short order and warranty it for a year... It is not the OEM but some of these places are decent - when they specialize on a brand or two: In my experience, those who say they can repair ANY drive typically do bad job on most.


The reason A-B stopped supporting the 1336s is that many of the components used to make the boards are no longer made themselves. So many repairs done by 3rd parties are now done with, at best, NOS (New Old Stock) components and at worst, used parts scavenged off of other bad drives. So sure, they give a warranty, but you are still living on borrowed time because you may fix one part, but another one was just as old.

1557 drives are Medium Voltage. PLC Center and Electrical South don't repair boards for Medium Voltage drives last I checked, too much liability.


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## Mike_kilroy (Sep 2, 2016)

DON'T GET ME WRONG! I AGREE WITH YOU GUYS!

Heck over 1/2 my business is retrofits of all kinds and brands of obsolete old motors, drives, VFDs, and spindles.

But another large percentage is repairing our old drives. Back when the 1336 was going obsolete, so were our Kollmorgen servostar drives. Over a number of years we bought over 500 uproc control cards so we could repair these. Our stock is running low, but fortunately we almost have our patentable electronic geared resolver unit ready. About 1/3 of our aerospace customers have drives they cannot replace without this gadget I am making. So repairs are their only choice - other than a full CNC controls retrofit also - @ approx. $ 400,000.00 per machine! 

But some customer sometimes also have good reasons to keep their old obsolete drives, or insist on repairing them. My point was just that there ARE 3rd party places who repair even the 1336's.


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## glen1971 (Oct 10, 2012)

JRaef said:


> Those 1557s can't be repaired any more either, someone should think about upgrading, because typically when anything is run by an MV drive, it's important to your livelihood...
> 
> I have a refinery client with two of them as well and although they too are still running, the operations people are increasingly nervous. Management won't cut loose of the cash though, they insist on limping along, "just one more year"... for 5 years now. Yet if one of them goes down unexpectedly, the losses and fines will add up to millions in a matter of hours. It's so foolish it hurts.


I've been on that band wagon for about 8 years now.. They got one 1557 replaced with a 7000.. Unfortunately they kinda dropped the ball on it, and undersized it so it changes the start-up on it now.. They figure that with the one replaced they'd have all kinds of parts. I said great but there's two problems with that.. Of the three drives, one is a 6 pulse and 2 are 12, so all the parts aren't interchangeable. And you can have all the spare parts you want, but if no one knows how to put them in and properly set them up, they are useless..


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## paulengr (Oct 8, 2017)

There are three weak spots in a VFD. The first is the power semiconductors themselves. We're on third and some fourth generation IGBTs now. The device first came out in the early 1990s. Consistently devices change generations every 10 years more or less. So the manufacturers get supply contracts for 10-15 years and generally support a sale for at least ten years after you buy it. If you are at the beginning of a "generation" maybe you get a full 20 years. Either way then the manufacturers usually design the board for 100,000 hours if operating life. I know one that purposely oversized their drives to push 20 years but that was a special case.

Second issue is as mentioned bus capacitors. Usually these are electrolytic types because that is the cheapest and smallest for a given capacitance. The electrolyte inside (glycol) saturates a paper layer that separates the layers. The end is crimped shut. Over time the glycol dries out and eventually you get leakage and then damage around the ends. This happens in 8-10 years. Metal film capacitors are dry and have indefinite lives. Oil filled is similar despite needing seals. But since these are physically larger the only place I know they are used is in traction (locomotive) drives such as modules from Semikron, one of the 3-4 actual component manufacturers.

Finally the solder joints are another weakness in the power side. There are some compression connections and even sintered joints in use in some equipment but its not common (again...traction drives). Otherwise the limit on soldered joints seems to be around 14-15 years or about 150,000 hours. Its sort if a holy grail to find a way to beat the thermal cycle limit on soldered joints as this affects virtually all electronic devices.

These are all averages of course and based on 10% failure rates so it is possible to easily beat these numbers or suffer early deaths.

So it is possible to make a 250,000 hour drive but parts support, size, and overall cost make it uneconomical except in utility and locomotive markets willing to pay a lot more for longevity.


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## JRaef (Mar 23, 2009)

You left out another crucial component; the "pre-charge circuit". On small drives and very large drives, the pre-charge circuit is usually a resistor and bypass contact. Failure of either component results in failure of the DC bus caps in short order. Some mid-range drives use an SCR front-end to ramp power into the DC bus and thereby don't need the resistor and contact, but that's not economic in all frame sizes.


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## paulengr (Oct 8, 2017)

JRaef said:


> You left out another crucial component; the "pre-charge circuit". On small drives and very large drives, the pre-charge circuit is usually a resistor and bypass contact. Failure of either component results in failure of the DC bus caps in short order. Some mid-range drives use an SCR front-end to ramp power into the DC bus and thereby don't need the resistor and contact, but that's not economic in all frame sizes.


Its worse than that. Large drives don't even usually have one by default and you have to add one in the design phase. And for whatever reason as stated they are usually a really cheap (as in costs lots of downtime) design. So they are very touchy about transformer sizing too since as stated, its just a contactor, a diode, and a resistor. Often hidden by a door in some obscure place, and often left off the schematic.

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## sparkiez (Aug 1, 2015)

I'm curious on the precharge circuit. Is that resistor in place to limit inrush and protect the electronics in the drive?


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## JRaef (Mar 23, 2009)

sparkiez said:


> I'm curious on the precharge circuit. Is that resistor in place to limit inrush and protect the electronics in the drive?


Yes, if you count the DC bus capacitors as "electronics". Capacitors charge themselves by drawing current at the available fault current level. That can cause such a sharp increase (high DI/Dt) that the capacitors themselves will swell and fail. So the resistor is put in series as a "current limiting resistor" for the first few cycles, then shorted out. Small component class "throw away" drives will often use an NTC thermistor instead of a plain resistor, because an NTC (Negative Thermal Coefficient of resistance) starts out with a high resistance and as it heats up, the resistance drops. So that eliminates the need for the bypass contact, but increases the likelihood of failure over time.


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## Tonedeaf (Nov 26, 2012)

heat is the biggest killer of VFD in my experience....most of the ones i replace are in enclosures with poor ventilation or are jammed in tight space with little ventilation.

In the one plant i work in we replace some drives once or twice a year.


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## glen1971 (Oct 10, 2012)

Tonedeaf said:


> heat is the biggest killer of VFD in my experience....most of the ones i replace are in enclosures with poor ventilation or are jammed in tight space with little ventilation.
> 
> In the one plant i work in we replace some drives once or twice a year.


We did a 1500 hp drive and put a 10 ton AC unit, which was properly sized for the heat loads, in for the MCC Building.  Well some consultant figured you could save some money by running it less and he told the operators to turn it up because he read that electronics were ok to run up to 40C (104F). I think it was 27C (81F), or warmer, in the building the last time I was there.. Way too hot in my opinion. Well low and behold they had to start repairing the drive more often. Someone even added 2 - 10" exhaust fans thinking it would help. If they had only lowered the thermostat setting to 21C (70F) the problem would have been fixed without the fans and without the down time..


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## JRaef (Mar 23, 2009)

Heat x time = failure...

40C is usually the MAXIMUM design limit of the ambient air surrounding a VFD, that's true. But setting a room A/C unit to 104F is nuts, because by the time the thermostat registers the 104F value, the uppermost layer of air is likely ALREADY much higher, and then by the time the A/C unit can pull the average temperature back down, the VFD components have been stressed. That was some brilliant engineer... He obviously missed his class on thermodynamics!


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## paulengr (Oct 8, 2017)

Every 10C or 18F doubles the life of electronics.

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