Author Topic: Help setting RPM and frequency on a VFD  (Read 760 times)

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Offline Houseman

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Re: Help setting RPM and frequency on a VFD
« Reply #25 on: August 05, 2019, 09:25:10 am »
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?
Hi 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.
 

Offline Houseman

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Re: Help setting RPM and frequency on a VFD
« Reply #26 on: August 05, 2019, 09:29:47 am »
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?
Hi 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.

FIRST 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 You
Thank You
 

Offline pansku

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Re: Help setting RPM and frequency on a VFD
« Reply #27 on: August 07, 2019, 07:36:10 pm »
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 output  |O If 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€.

 

Offline sibeen

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Re: Help setting RPM and frequency on a VFD
« Reply #28 on: August 07, 2019, 08:46:48 pm »
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.

« Last Edit: August 07, 2019, 08:53:08 pm by sibeen »
 

Offline pansku

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Re: Help setting RPM and frequency on a VFD
« Reply #29 on: August 07, 2019, 08:54:40 pm »
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 - use a UPS to feed the VFD. 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.



The 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%/1c :) Unfortunately the details and scope shots in those are confidential  :-BROKE
« Last Edit: August 07, 2019, 09:13:25 pm by pansku »
 

Offline sibeen

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Re: Help setting RPM and frequency on a VFD
« Reply #30 on: August 07, 2019, 09:03:01 pm »

The 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.

Ahh, that would be a great fix then and I would certainly try something like that before going down the UPS route.
 

Offline pansku

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Re: Help setting RPM and frequency on a VFD
« Reply #31 on: August 07, 2019, 09:31:04 pm »
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 topic  :-//

Those are "worst-case scenario" tests regarding cables, filters, supplies, loads etc. to prepare for official testing. So real world performance should be even better.




« Last Edit: August 07, 2019, 09:48:35 pm by pansku »
 

Offline StillTrying

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Re: Help setting RPM and frequency on a VFD
« Reply #32 on: August 07, 2019, 10:47:25 pm »
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,

All of the photo's show the pump current drooping with the voltage droop, but I do think all the spikes at the end of the droop are caused by the pumps themselves.
CML+  That took much longer than I thought it would.
 

Offline StillTrying

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Re: Help setting RPM and frequency on a VFD
« Reply #33 on: August 14, 2019, 12:57:31 am »
Has any fix or explanation for the drooping voltage been found?
CML+  That took much longer than I thought it would.
 


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