# VFD lifespan



## V-Dough (Jul 22, 2014)

Is there a recommended time after a VFD should be changed out?
Years or hours of power on or run?
I had one out of 4 Powerflex 70 VFDs go bad with all 3 phases short on the input. There are parameters that give power up hours as well as runtime hours. 
Theyre all about 15 years old with 125,000 hours power on and 15,500 hours runtime. The VFDs drive lifter motors and are oversized quite a bit for the application.


----------



## Sblk55 (Sep 8, 2017)

V-Dough, do not know of recommended time, but when we started getting failures we contacted AB and was told pretty common after 10 years to stare having DC buss issues.

Steve


----------



## JRaef (Mar 23, 2009)

DC bus capacitors are typically going to last 7-10 years with power applied continuously*. After 10 years you often get lucky, but you are living on borrowed time. Bus caps can be replaced of course, but as a general rule after 10 years, the components change and buying ones that fit and the time to replace them will likely cost more than a new drive (depending on size).

Another factor is how many times a VFD has been powered down and back up, because each power-up stresses the "pre-charge" resistor (depending on design) and once that resistor fails, the caps fail shortly thereafter. So for example most drives that use a pre-charge resistor will rate them at 1,000 power cycles. Once per week (1,000 weeks) is pushing 20 years, but once per day equates to around 3 years.

I'd say that if you got 15 years out of your PF70s, that's pretty good. If the line side appears shorted, that probably indicates that the caps failed and shorted the diode bridge. Wouldn't be worth repairing in my opinion, just buy a new one. PF70s are still a valid product.

*Leaving a VFD un-powered for over a year means the caps may fail the next time you just energize them (even with no load applied yet). If a drive has been on the shelf or otherwise idle for over a year, you need to perform a "reforming procedure" on them before fully energizing them again. most VFD mfrs will give you instructions on how to do that.


----------



## varmit (Apr 19, 2009)

From my experience, I would say that 7 years are about an average life for a VFD. I agree with the conditions and variables that JReaf noted having an effect on VFD lifespan.

That said, I once encountered an old Baldor SP-500 on a 2 HP motor on a bag filling machine that someone had wired the incoming line power, to the drive, through a contactor. The VFD was powered down and back up on each bag fill- thousands of times a day for 3-4 years. I wired it correctly and it then lasted another 6 years. I was impressed with this drives toughness.


----------



## Peewee0413 (Oct 18, 2012)

Totally agree on the repeated charging of the dc bus. I've seen gs2 drives fail after a year repeatedly because people hit the Estop to stop the line. The estop dropped the mains via a contactor. After some circuit changes the drives quit failing.

Sent from my VS995 using Tapatalk


----------



## paulengr (Oct 8, 2017)

Here you go.

https://www.linkedin.com/pulse/life-span-vfds-paul-campbell

I’ve seen threats of 2 years about bus caps but not less than that. In practice I’ve never seen them fail unpowered in under 3 years. A little tantalum pretty much makes it go away long enough to pass 3-4 year extended warranties.

Typically I’m seeing most VFDs are dead on arrival at around 12-15 years.

In wastewater, sulfuric acid, and paper plants I don’t know what Rockwell is doing different but 18 months is not unusual compared to 8-10 years with the old 1990s vintage ones. Same places the Altivar 61s are 5-10 years. Too soon to tell on the 750s or 525s or Altivar 600 series. Current generation Tecos (EQ7, F5xx series, N3s) are cheaper and hold up better over time but the most feature rich drives currently on the market are Altivar 600 and 900 series.

You can beat these odds and some traction drives based on the upper end of Semikron modules can hit 200,000+ (20+ years) availability based on 90% survival rate and the modules are interchangeable. Of course they are about 3 times the price and infant mortality is high with the sintered construction process (no solder). Using oil filled, polymer, or metal film capacitors gets past the first age limit but eventually thermal cycling on solder joints is the limit, made far worse when hydrogen sulfide is around even with conformal coating.

I’m a certified drive technician but we distribute 3 drive lines, are the authorized service center for 5 lines, and I work on pretty much all of them. I’m going by what I actually see every week on the job, not sales.


Sent from my iPhone using Tapatalk


----------

