Help setting RPM and frequency on a VFD - Page 1
Forum section: electronics / general

author: Houseman
author_rank: Regular Contributor
timestamp: July 23, 2019, 12:26:44 am
content: Hi.I have a three-phase 400V - 50Hz asynchronous motor that at full speed directly-connected is reaching 1440 RPM.If I want (have) to pass it through a VFD which is the setting I have to input in the SPEED PARAMETER OF THE VFD (0-2800)?Default is 2800, but do I have to set it to 1440?And the Working frequency? (0-400) with 400 set.Do I have to tune it to the 50 mains frequency?Sorry for the mess.Best regards and thanks all

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2019, 12:32:45 am
content: Can you find a manual for the VFD? The speed of the motor is directly proportional to the frequency. The ones I have let you set the frequency or the percentage of nominal and you can also set the range so you don't exceed the mechanical capabilities of the motor. If you give a 50Hz motor 400Hz it will run at 8x the normal speed and some motors can fly apart catastrophically or flash over at the higher voltage needed to keep the current up.

author: sibeen
author_rank: Frequent Contributor
timestamp: July 24, 2019, 10:45:23 am
content: Houseman, in this case the best and only advice I can give you is RTFM (read the ******* manual).

author: Houseman
author_rank: Regular Contributor
timestamp: July 24, 2019, 03:55:50 pm
content: Quote from: sibeen on July 24, 2019, 10:45:23 amSibeen... have done it already. But it has only parameter sheets and wiring diagram.So I needed your helpAttached the manual in question.Regards

author: Stray Electron
author_rank: Super Contributor
timestamp: July 24, 2019, 10:08:28 pm
content: The manual appears to say that parameter P21 controls the motor RPM and that a setting of 2800 gives 50 Hz. Also setting parameter P62 = 2 will make the display show the RPM. The control appears to also have six "ramp up/ramp down" speed settings, P26 thru P32.You can probably get better answers at the Garagejournal forum.

author: james_s
author_rank: Super Contributor
timestamp: July 24, 2019, 11:26:06 pm
content: The VFD is going to have to know how many poles the motor has in order to determine RPM. That will be a setting somewhere too.

author: Stray Electron
author_rank: Super Contributor
timestamp: July 25, 2019, 01:12:19 am
content: That's what I thought too but it appears that they make an assumption about the number of poles.

author: Houseman
author_rank: Regular Contributor
timestamp: July 25, 2019, 08:16:35 am
content: Do You think that fiddling around with the parameters and trying will ruin my motor?what I need to be care of while playing with the settings? Current consumption?Best regards and thanks to all you for your answers

author: james_s
author_rank: Super Contributor
timestamp: July 25, 2019, 03:59:29 pm
content: I think it's unlikely, just don't let the speed go up to crazy levels. I've played around with several VFDs without any issues.

author: Houseman
author_rank: Regular Contributor
timestamp: July 26, 2019, 02:52:23 pm
content: Thanks Jame-s.For all aficionados let's tell you the inglorious end of my VFD.Without load applied on the shaft it worked like a charme: the default settings were enough to let it spin smoothly at the right speed: setting parameter to 2800 its rpm were as nominal (thanks to all for the contribution).Once I hard-connected the motor to the mechanical load (a vacuum pump) the first time I let it run it tripped, (short circuit protection) then at the second time the magic smoke (Dave's say) escaped from the VFD and the MSOFET popped.The manufacturer of the pump forbid me the ramp-up startup due to possible mechanical failure of the internal vacuum mechanism.Since the high current draw at startup (6x more than nominal) due to the initial torque of the mechanical part the MOSFET could not withstand the high load so POP!!And I was thinking I was in a safe zone buying a 4kW Inverter for a 2kW motor, hoping that it would be enough....I attach the voltage/current draw at startup.Now the question:Should I really need a 15kW inverter for a 2,2kW motor to withstand the current inrush?Are there any workaround to bypass it?Thank you all again for your kind support

author: pansku
author_rank: Regular Contributor
timestamp: July 26, 2019, 05:35:38 pm
content: When you say forbid do they mean like completely or are very short ramps allowed?Typically for VFD's there is a spec for I max which is a but bigger than continous use. Some manufacturers can also spec like 180% or 200% starting torque. Like for ABB ACS880 the 4kW model can supply 12,2A for 10 seconds at start up or longer if enviroment allows, but 10A nominal for continous use and 4kW Vacon 100 has a spec of 16A for 2s at start. Thereshouldbe local sales people with technical knowledge at reputable brands that can help you with the selectionDisclaimer: I work on the ACSx80

author: Houseman
author_rank: Regular Contributor
timestamp: July 26, 2019, 09:58:00 pm
content: Quote from: pansku on July 26, 2019, 05:35:38 pmPump manufacturer forbid me to use ramps start up since the original concept is a three-phase asynchronous motor directly connected to the electrical line in order to give the most initial torque to begin movement of the internal blades and to withstand the initial friction. A ramp would glue or worst bend the blades to the external chamber. I honestly don't know if with the ramp the motor would even start spin: once you power off the motor shaft gets in stop position in less than half a rotation!!Thanks for the suggestion. Will talk to my local ABB referee and find a suitable solution for that. From you answer I understand that there are no solution otherwise than considering the inrush current and find the suitable capacity at 200% load.Do you think that (if possible) a ramp would have withstand the initial momentum?Best regards and thanks

author: james_s
author_rank: Super Contributor
timestamp: July 26, 2019, 10:25:24 pm
content: Is this a really cheap VFD? I have a couple of small Omron units, and another I forget which brand, all of them Japanese I think. At my friend's machine shop we have loads of VFDs ranging from 1kW up to around 20kW and none of them have ever blown up. Usually they are quite well protected and will shut down if abused rather than let the smoke out.

author: pansku
author_rank: Regular Contributor
timestamp: July 27, 2019, 06:18:38 am
content: Quote from: Houseman on July 26, 2019, 09:58:00 pmAs I said, the sales people should have technical knowledge. Unfortunately sometimes you can end up chatting with a summer intern who doesn't have the confidence to ask engineers at the company for help. I think you should propably ask for example Siemens, Danfoss or Schneider if you don't get satisfying help.On the DTC controlled VFD's I personally think that a short (maybe around a few seconds) ramp shouldn't be an issue. For example we run the vacuum pumps on our surface electron microscope on VFD's with a some sort of ramp. However I'm not an expert in vacuum pump technology. I mostly do stuff other than application engineering.DTC ramps are completely different than V/F(scalar) ramps. The DTC (or whatever other manufacturers call their flux sensing technology) provides full torque at standstill unlike scalar. Thar is why I think the short ramp should be fine.Btw what type of vacuum pump are you running? I'm not sure if 100% oversizing is the way to go. I just used those examples to demonstrate that different vendors can have quite varying specs for startup boost. I can maybe do a bit of research regarding the sizing next week in our lab and ask some of my more experienced collegues. They should have more knowledge about these sort of things because they sometimes go do measurements at the customers site and stuff like that.

author: cs.dk
author_rank: Unknown
timestamp: July 27, 2019, 12:09:59 pm
content: Quote from: Houseman on July 26, 2019, 02:52:23 pmNo.. Most VFD manufactures specifies only to go one size down. Ie. a 4 kW motor on a 5,5 kW drive is OK.The drives themselves are prepared for the inrush, and should be for obvious reasons. For example, if you have a heavy load, and almost no ramptime, the inverter won't release the smoke.Sounds like a crap inverter.Grab a ABB, Omron/Yaskawa, Lense or similar.Are you sure about star/delta configuration on the motor? Post a picture of the motor typeplate if in doubt.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 27, 2019, 07:45:36 pm
content: A mechanical overload cannot break a VFD. Internally, the MOSFET or IGBT cannot die of overcurrent, because the current sense circuit turns the gate off before the current rises, in microseconds. You did nothing wrong.The VFD was broken already. Either it has a manufacturing defect, or a design defect. If latter (it does happen), we call this phenomenon "broken by design". If this is the case, it's not a VFD - it's a dummy box fraud. Return it and ask for money back. Tell us the brand so we know what not to buy.Claimer: I design these things and would be very sorry if I fucked up the basics 101.

author: pansku
author_rank: Regular Contributor
timestamp: July 28, 2019, 11:51:12 am
content: Quote from: Siwastaja on July 27, 2019, 07:45:36 pmI assume this was meant for meI'm still a bit new to AC drive technology as you may know not all the jobs require prior knowledge about them. Sorry if I spread misinfo. I just made the claimer to be transparent when bringing our products to discussion

author: Siwastaja
author_rank: Super Contributor
timestamp: July 28, 2019, 11:53:30 am
content: Quote from: pansku on July 28, 2019, 11:51:12 amNo, I replied to the OP who seemed worried about the VFD blow-up possibly being their own fault, or something like that, possibly.Basic IGBT/MOSFET protection of course comes regardless the control algorithm.

author: cs.dk
author_rank: Unknown
timestamp: July 28, 2019, 12:24:50 pm
content: I just read the manual.. a 4 page job, no vendor name or similar. Toss it.Most quick start guides on ie. an Omron is 60-100 pages..

author: Houseman
author_rank: Regular Contributor
timestamp: July 29, 2019, 08:47:49 am
content: Quote from: Siwastaja on July 27, 2019, 07:45:36 pmHi it was a cheapo Chinese Acogedor brand one you can easily find for small cash on Amzn.. I know I should have asked for more reliable stuff but the fact that we were trying if the VFD would block the electrical noise from source (see other post) , brought me to the idea to first try this one, without letting my customer spend 1000USD just for trying... Now I know he has to spend it...The failure sequence was:Turn inverter on OKPress Start: first try was succesful. Pump rotated smoothlyPress Stop: OKPress Start Again: Error 1-Short Circuit protection (motor does not move)Press StopPress Start again: POP-Fizz-Magic Smoke.THE END

author: pansku
author_rank: Regular Contributor
timestamp: July 29, 2019, 04:41:54 pm
content: I did some quick asking around the lab today. At least for our small ~1kW vacuum pumps we use 5sec linear ramp to a minimum speed specified by the pump manufacturer for startup. I'm assuming your pumps are liquid ring type unlike ours? I heard that the ramps should be fine for those too, but just beware of the minimum rpm and get past that point. That one's with a grain of salt as we aren't vacuum pump experts.Depending on the process ie. does it have frequent starts or just static running, you should be on the extra safe side when using the light overload specification by VFD manufacturer. Just pay attention to the so called "frame size" of the unit. If you have, lets say, size 2 frame with 3kW and 4kW models and size 3 frame at 5kW. The price difference between the first two units can often be neglible in a small installation, but the same 1kW jump to size 3 would often cost you a pretty penny. Those numbers are just an arbitary example and oversizing usually won't do you any harm but at least on premium devices it usually doesn't do anything useful extra either.This is assuming we are on the right ballpark. Huge overcapacity means that current transducers are oversized and that can lead to poor motor control perfomance and at worst it limits you to use scalar control. Coming back to the ACS880 (which is way overkill for your application) that limit on being able to use vector control without triggering a warning is around 1/6 of nominal current. I'm not sure what limits other vendors put in their products.

author: mzzj
author_rank: Super Contributor
timestamp: July 29, 2019, 07:17:05 pm
content: Quote from: cs.dk on July 27, 2019, 12:09:59 pmHear hear.Problem and solution.

author: Houseman
author_rank: Regular Contributor
timestamp: August 03, 2019, 05:25:52 pm
content: Quote from: pansku on July 29, 2019, 04:41:54 pmThank You Pansku for your explanation.The pump in question is a Leybold Trivac D40BI attach the specs.We have finally chosen an Omron V1000 7,5kW with autotuning.We have chosen the V/f control.Sounds it works great, with the 0.0 sec ramp up.Even the vacuum (5x10exp-3) get quicker than without the inverter.Do you thing we could fiddle al little bit around with velocity?Regards

author: pansku
author_rank: Regular Contributor
timestamp: August 03, 2019, 07:23:30 pm
content: I'll take a closer look at the documents when I get back home to a computer from my summer cottage. Regarding the VFD settings, what lead to the decision to use scalar control? I also had a quick look at your other thread. Now that you have the increased dc link capacitance of a larger drive, how is the power loss ride-through configured?

author: cs.dk
author_rank: Unknown
timestamp: August 04, 2019, 10:34:59 am
content: Quote from: Houseman on August 03, 2019, 05:25:52 pmGood choice - V1000 is really a great VFD. Lots of programming options to. You'll be happy with it

author: Houseman
author_rank: Regular Contributor
timestamp: August 04, 2019, 11:25:10 pm
content: Quote from: pansku on August 03, 2019, 07:23:30 pmHi Pansku. Sure, take your time.Regarding VFD setting scalar control:Since I know nothing, I have talked to Omron support after explaining the problem. Any suggestion are welcome, of course.[how is the power loss ride-through configured?] please cannot understand. Is there a way to set it? Please explain. It would be very glad to isolate the motor from the power outage since for now the power loss simply ride through directly.Have a nice summer-cottage relax, of course.Best regards and thank You.

author: Houseman
author_rank: Regular Contributor
timestamp: August 04, 2019, 11:29:47 pm
content: Quote from: Houseman on August 04, 2019, 11:25:10 pmFIRST OF ALL READ THE MANUAL.I have seen on the manual what are you saying regarding power loss ride-through.Now I need to understand more. Thank YouThank You

author: pansku
author_rank: Regular Contributor
timestamp: August 07, 2019, 09:36:10 am
content: Hi,About fiddling with the velocity, I don't think you'll run into trouble trying to run it faster or slower as it's rated for 60Hz using the same motor. That just depends on the available grid voltage. For minimum speed I'd stay above 60 or so percent to ensure working lubrication.Usually using vector control is recommended by many manufacturers as it offers better control over the process. Often the OLV (open loop vector contol) relies on the calculated motor model. As I have understood your application requires high starting torque so the Yaskawa can't perform the necessary autotuning without disconnecting the motor from the load. In your case that could lead to smoother acceleration when the pump presents a heavy load. If that is possible, I'd suggest you go ahead and do that for what is about to come next.In page 136 on the manual details on PID operation begins. If there is an electronic pressure meter available (0-10V or 4-20mA) PID could be used with upper and lower frequency limits, PID softstarter and PID sleep function. Or you could use the Energy saving control. Both of those modes work best with OLV.Those operating modes are just a bonus for using a modern drive. The is no need to use them unless you want to further optimize the process to keep a stedy vacuum in changing load conditions or just to find energy savings.I took a quick look at available settings for the power loss ride-thru on the V1000. I don't think that there is a magic bullet for your voltage sags. Some drives with regenerative braking can offer voltage boost when voltage sags but phases are not lost. Unfortunately those devices are expensive and meant for different kind of processes usually with high inertia loads and constant accelerations/deaccelerations (like cranes or elevators). One trick you can use depending on the facility is to use multiple drives with the DC links connected together to increase available capacitance.Here is a picture from marketing materials to illustrate what I mean. Unfortunately I was unable to find the specifications for that. I think it was 380-415V +-10/15% to full outputIf that is to any interest, I'll ask one of the main designers. But those things are expensive, a 5,5kW nominal model propably costs over 1300€.

author: sibeen
author_rank: Frequent Contributor
timestamp: August 07, 2019, 10:46:48 am
content: pansku, I may be wrong, and it certainly wouldn't be the first time, but what you're showing in the photo is not really to overcome voltage sags, which are a short duration event, but to overcome the effect of a voltage drop along a long run of cable. In this a regenerative drive is an active front end style rectifier (really converter) and can adjust the DC voltage at its output to its nominal value even when the input voltage to the drive has fallen due to voltage loss across the incoming cabling. So this is basically a long term, slow moving event that the drive can overcome. I'm not sure the firing sequence of the rectifier would be set up to handle voltage variations of less than 100 ms or so.Houseman, I saw your latest post over in the other thread - bugger. It may be time to get a UPS. This is where I'm quite loathe to offer advice on a system that I've never looked at or examined. You often try to diagnose something from afar, spend time ripping your hair out, and then the 'client' mentions in passing, "oh, did I forget to tell you that the bingleplane fluxcapacitor is also connected upstream of the floogleplex unicator"?From the photos you shared a wee bit of explanation - the initial voltage dip cause the slip of the motor to change which causes the current into the motor to increase. This caused the voltage drop across the cabling feeding the motor to increase causing the voltage to drop - etc, a bit of a positive feedback loop and what you would expect to see at the input of a motor.So remembering that for free advice you get what you pay for. You will need to oversize the UPS for the motor (3kW?). You probably need to talk to one of you local UPS companies. Go direct for the technical advice, not through a reseller. UPSs generally come with a 10 minute autonomy (back-up time) as standard. You don't need anything like this, especially if the UPS is over sized. This can cut down the cost of the UPS system by quite a margin as a substantial part of the cost of a UPS is in the battery. You only need a minute or two of autonomy time and this only sized for the motor and not the size of the UPS. Operational wise I'd start the motor whilst the UPS is in maintenance bypass and only once the motor is up to speed transfer across to the inverter.Speak to the manufacturers. Some UPS makers will have special inverter firing schemes that they can use if the UPS is to be used to supply a motor rather than a standard switch mode power supply and can reprogram the UPS to make use of these firing schemes.

author: pansku
author_rank: Regular Contributor
timestamp: August 07, 2019, 10:54:40 am
content: Quote from: sibeen on August 07, 2019, 10:46:48 amThe photo is indeed for long term effect, I had some troubles finding right words so I just put that out there. One of the engineers working on the project at least thinks that the short sags are just as fine. I'm trying to find our documentation about actual testing for such events.Edit: I found the verification test reports and measurement result. The DC link voltage boost is so fast that it has subcycle response time to network sags when tested with 80% input voltage 250 cycles. 70%/25c, 40%/10c, 0%/1cUnfortunately the details and scope shots in those are confidential

author: sibeen
author_rank: Frequent Contributor
timestamp: August 07, 2019, 11:03:01 am
content: Quote from: pansku on August 07, 2019, 10:54:40 amAhh, that would be a great fix then and I would certainly try something like that before going down the UPS route.

author: pansku
author_rank: Regular Contributor
timestamp: August 07, 2019, 11:31:04 am
content: Here is what I can share of an unnamed regenerative or low harmonic drive around the same size as the Yaskawa of OP. Unofficial testing according for SEMI F47 recommended 100sec on 89% of nominal load. Sorry if you find this too commercial to this forum and out of topicThose are "worst-case scenario" tests regarding cables, filters, supplies, loads etc. to prepare for official testing. So real world performance should be even better.

author: StillTrying
author_rank: Super Contributor
timestamp: August 07, 2019, 12:47:25 pm
content: Quote from: sibeen on August 07, 2019, 10:46:48 amAll of the photo's show the pump current drooping with the voltage droop, but I dothinkall the spikes at the end of the droop are caused by the pumps themselves.

author: StillTrying
author_rank: Super Contributor
timestamp: August 13, 2019, 02:57:31 pm
content: Has any fix or explanation for the drooping voltage been found?