Powerflex 753 VSD

Thank you kindly for your answer, I do understand what coasting is , but when it changes from high speed to low speed it is definitely being controlled by the vsd, it is not coasting. I could not find anywhere on the manual showing how this time is determined.

Coast time relates specifically to the stop command, the time it takes the drive for switching from one speed to a slower speed is dictated by the deceleration parameter and this parameter should be set to a realistic time depending on your load's inertia.

Given its a fan the deceleration should be set to something like a few seconds not a few tens of seconds if it were big heavy load.

Maybe the thrust reverser will need to be deployed?

There is such a thing as TOO much information. KISS and all.

Thank you-We use AI to set speeds, we can set any speed between 400RPM to 1750RPM, we mainly select between two speeds.1750rpm and 1000rpm.

As usual a perfect answer Jraef……your answers are clear, informative and comprehensive…unlike few other gurus here who will first tell you call the manufacturer or read the manual….and give similar wisecrack answers….I am sure everybody is wise enough to do that before posting the question here. Thanks again,..and keep up the good work.

I am sure everybody is wise enough to do that before posting the question here.

<cough>

I almost choked on my morning mug of Disprin.

That's why you should reread post 1 and give it a GA.

How did the phone call with the equipment supplier go? Any joy there?

No need to bother the manufacturer for a simple fan load deceleration setting question answered above, in the manual and application notes and with a simple test in the field.

I believe most of you misunderstood the question. When stop command give it will coast-that is simple. While running say at 50Hz you decide to go to 30Hz. This is the time I am interested in. I was looking at increasing this time, but I cant seem to find any time adjustment unless I select a ramp stop. I don't have a issue with stopping but more so an issue when I change speed.

Again, that's the deceleration speed setting when changing from one set speed to a slower set speed.

Looks like you were right. No matter how much added info I gave in order to educate him as to what was going on, he still didn't get it.

I surrender...

Looks like you were right.

Well I would hope so, I used to sell, test and repair the blessed things AND I consulted a VSD manual before answering just to be sure.

The next best thing would be talking with the specific VSD manufacturer's Engineers, but they would have just said RTFM or ignored such a simple question.

I surrender.

Never surrender. Give up, possibly, but never surrender.

IMHO, I believe the real problem is that you do not understand the very good answers you have received.

Re-read,and re-read,and re-read the answers,especially JRAEF,who gave a very clear and concise, not to mention,simple answer to your question.

If after reading at least 10 times,you still do not understand that your question has been answered,then no explanation is possible.

If that is the case,I can understand why you post anonymously.

I have posted anonymously in the past,in moments of weakness,but eventually I reclaimed the post, and a light was shone upon my island of ignorance,and I was wiser for it.

We are all willing to help those that are willing to help themselves.

There is no shame in not knowing, only in not wanting to dig for the knowledge,and wanting someone else to spoon feed the Pablum to you.

Confucious say:"God makes the apple tree,but you must pick the apples yourself."

Thanks-seen it on Jraefs post, Had to read it a few times.

"I believe most of you misunderstood the question."

Does the aforementioned "we" include subordinates ? You think your job is stressful!

OT , but....

"The acceleration time will determine the speed change from low to high."

What is this supposed to mean?

I'll decode for you.

"The fan coasts when it stops", so it never really stops, it just coasts.

"It is also set to run on high speed or low speed" so when it runs on high speed or low speed it is not coasting. When it does coast, it may be coasting on high speed or low speed. We'll ignore friction, air resistance and logic.

Now, it gets a little complicated here."acceleration time will determine the speed change from low to high". This is brilliant! A classic example of Newton's second law.

"Can someone tell me how the time is determined from high speed to low speed" This will require the application of Dumbo's fourth law of Truboencabutation to determine the rate, over time, divided by the equatorial declination of the earth in relation to the orientation of the fan at rest, if ever.

In short, Anonymous Posters should be banned.

Well, I'd have thought that the equipment manufacturer can and that it was worth a phone call to find out. Then, I'm funny that way.

Doesn't it say so in the manual, then? How strange.

Parameter 537 Decel Time 1 is the time it takes for the Drive to decelerate from NP Speed to 0. i.e. if it's a 50 Hz motor and you want to decel from 50 to 30, that's 40% of the Motor speed and if 537 is set for 10 seconds, it should take 4 seconds to decelerate to that speed.

There are other factors at play here, especially with a fan application, the drive will try not to let it's bus voltage go to high so depending on whether or not there are Dynamic Braking Resistors or not, potentially other fans running in a common plenum, and how the drive is set up, it may extend the decel time on its own to protect against over bus voltage.

Shawn

Interesting question - I can tell you how to know the set ramp down time to stop, and then with the coast option, Lyn's stop watch would be required, but if I read your question correctly, you want to know time between 2 preset speeds. I have never tried timing this in all the PowerFlex installations I've done, but think it is rather rapid. Very interesting question indeed. This should be a known time by Allen Bradley Tech Support, or calculatable given the parameters, such as speed presets, motor current draw and so on, as I would assume there is internal programming that regulates how quickly this can change based on load. Unfortunately, they are not free. We pay a yearly fee to consult with them on matters concerning AB equipment. Find someone with a contract for Tech Support and have them ask the question.

I believe the first few people who answered assumed the low speed was zero, but on Jraefs post I did find the answer.

"Parameter 537 is the "Decel Time" mentioned above. So IF you have told the drive that the Stop Mode was Ramp, this is where you give it the value. If however you told it that the Stop Mode was to be Coast, then this value is ignored, but ONLY with regard to a full Stop command."

Thanks everyone for all your answers, I learnt a few things from this post. Number one, next time I need to be more clear.

I've used PF VFD's for 10 years and programmed every blinking one of them and never had to be concerned with that particular parameter. (537) Never actually counted them, but I believe there are over 300 of them. You should try to program a non-VFD ready, should have been obsolete 15 years ago, motor where you have to change torque curves. Oh that is fun! (I think Jraef may have worked for AB at one time - he really knows their products)

As far as being clear is concerned, most of us, myself included, skim read these to get to what we think the problem is. (don't want to upset the boss too much if he catches me on CR4) I've learned to fully spell out the problem when I post a question. I've also tried to read a posted question thoroughly before sending out an answer, as I sure screwed some replies badly by jumping to a wrong conclusion.

Phys,

You apparently don't know it, but tech support for PowerFlex drives is free, you do NOT need a TechConnect contract. Logix and software support, yes. But anyone can call the Drives Tech Support hotline any time, no questions asked. After hours you have to leave a call back number and an on-call technician calls you back (however if you have the higher level TechConnect contract you get faster after-hours support for anything, including drives).

It's just not toll free. Two 6 Two-51 Two-817 Six (anti-bot format, figure it out).