PTO versus analog reference.

Hi everybody.

I was wondering what are the advantages of PTO control of a drive over analog control.

Up till now we are using only 0-10V as speed reference for the drive, however I noticed that some micrologixes come equipped with PTO , also some drives with pulse train input so I might use them.

How long can last an FET output? I know they are saying a lifetime, but what's a lifetime? for 1Khz reference and let's say 20 hrs/day, 360 day/year 10 years we have about 260 bilion cycles.
Any thoughts?

Thanks
Marian

From what I found up till now a solid state output have

"higher life time then mechanical relay"
20x more, 50x more , some 100000 hours or 11.4 years.
Still waiting for AB guys with their answer on ML1200 high speed output.

also that PowerFlex700 can get input up to 420Hz and F7 Yaskawa up to 32KHz ( quite a difference).

So nobody has an opinion about pulse train agains analog speed reference?( not for positioning,just feed material into a loop)

I guess I can't see why not to use the analog speed reference. Especially if it is not for positioning.

One reason is some Mlogix PLC's have a PTO on the main unit but if you want Analog you might have to buy an expansion module. With the PTO, you could save that cost.

For the moment I do not intend to use PTO.
However as Tackdriver pointed out ML1200 BXB for example has one output suitable for PTO/PWM, so no need to buy an extra analog card.
Other consideration could be noise issues. I guess PTO is better than analog about noise, but other people may say otherwise.

For me except life expectancy of the FET output i do not see another reason why I would not use PTO, but again is good to know before some pitfalls of a method before finding out on your own skin.