adccommunitymod (AutomationDirect) asked a question.
Created Date: October 31,2009
Created By: bblank
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Have a GS3 20hp 480v drive operating a 20 hp inverter duty motor operating a set 7 of drum roller's 10 "D x 11 'L with a lot of rotating mass, on acceleration when the drive reach's set point speed with no load on the drum rollers it will cause an overvoltage fault. I can not use anymore accel time than 4-5 seconds due to the process. I have installed a dynamic braking board and braking resistor to try and absorb some of the regeneration which did help some. If max hz is at 45-46hz it will ramp up and work alright, when at needed set point of 52-53hz it will overvoltage fault when there is no load on rollers. My input voltage to drive is high at times from ultility co, I have metered up to 503vac line to line. Wondering if anybody has any other idea's?
Created Date: October 31,2009
Created by: bfitz
Could you try an S-curve accel ramp or a stepped accel ramp? Both of these options should allow you to accelerate slower as you reach your target. Note that you will need to accelerate faster during the middle portion of the curve to maintain your 4-5 seconds total acceleration time. Also, many drives will let you add more than one resistor unit to increase braking torque. Might be something to check into.
Brian
Created Date: October 31,2009
Created by: milldrone
bblank,
Are you using P 1.03? (S curve) Try this first and experiment.
If no joy, try a more aggressive rate in P1.01 and P1.05 at a less aggressive rate (page 4-20 in the manual) and use P 1.07, P 1.08 to fine tune the change over.
Is P 6.04 set to 00? (auto voltage regulation) chances are this will not help.
Is P 6.05 set to 00? (overvoltage stall prevention) chances are this will not help.
What do you have in P 6.17? (overvoltage stall prevention level) chances are this will not help.
What do you have in P 6.18? (braking voltage level)? Be careful with this one you do not want your braking resistor on all the time! Monitor the DC bus voltage to get an idea of where to set this parameter. Set it just below the point the drive trips at.
I'm curious. Are you in sensorless vector or V/Hz mode?
Edit I see Brian beat me to the S curve thing!
Created Date: October 31,2009
Created by: bblank
Brian,
I have not tried this yet, due to my short accel time I did not think it would help, I will definitely experiment.
Thanks
Brett
Created Date: October 31,2009
Created by: bfitz
Brian,
I have not tried this yet, due to my short accel time I did not think it would help, I will definitely experiment.
Thanks
Brett
Brett,
I didn't spend much time looking at the manual, and I have no experience with a GS3, but it looked like you may need to change your accel time in a non-intuitive way if you are switching to the S-curve accel. It appeared to me that the accel time setting is the point in time when the s-curve kicks in, not the total accel time.
Milldrone will be much more help here.
Brian
Created Date: October 31,2009
Created by: bblank
Vaughn,
I'm going to experiment with the s-curve, also
I have 6.04 set at 00
6.05 set at 01
6.17 set at 850
and 6.18 set at 790
using V/Hz mode
Thanks,
Brett
also experimenting at the site I can ramp the roll's up to 45hz which works, and then when the load is added ramp up to desired freq(52hz) and all is fine until the load falls off and rolls are running empty then it will overvoltage. Working with s-curve settings will help with acel only? Which is a good start to my problem. then might have to work on it from there or is there something else Im missing?
Created Date: October 31,2009
Created by: milldrone
I'm going to experiment with the s-curve,
I do not know your process, but perhaps with a modified ramp as Brian and I suggested, you can tolerate the last finishing off part of the accell ramp(s) not being inside the 4-5 seconds you previously posted.
and 6.18 set at 790
Default is 760, I would not hesitate to set it there.
using V/Hz mode
I would not be surprised if going to sensorless vector solved the problem. In theory the drive "knows the speed of the motor ". No promises, it might make it worse.
Edit: The edit to your last post leads me to believe that lowering the braking voltage level is the answer.
Created Date: October 31,2009
Created by: milldrone
I 'm posting again to make sure that this response does not get "hidden " in an edit.
Read carefully parameters P 2.01 through P 2.03. The drive may be overcompensating (page 4-25).
Created Date: October 31,2009
Created by: milldrone
I should have included P2.00 in my previous post.
I also need to ask:. Are there any power factor capacitors any where nearby?
Created Date: October 31,2009
Created by: bblank
Vaughn,
There are no pf cap correction at this site, I understand what you are getting at with the previous post's, thanks for all the help, I will work on experimenting with these change's.
Thanks,
Brett
Created Date: October 31,2009
Created by: bfitz
Vaughn,
I'm going to experiment with the s-curve, also
I have 6.04 set at 00
6.05 set at 01
6.17 set at 850
and 6.18 set at 790
using V/Hz mode
Thanks,
Brett
also experimenting at the site I can ramp the roll's up to 45hz which works, and then when the load is added ramp up to desired freq(52hz) and all is fine until the load falls off and rolls are running empty then it will overvoltage . Working with s-curve settings will help with acel only? Which is a good start to my problem. then might have to work on it from there or is there something else Im missing?
This is critical. You are changing the load on the drive. A V/Hz drive will just keep putting out voltage at the specified frequency without knowing that the motor slip is decreasing rapidly. An S-curve will help you approach a set speed with minimal drama, but the situation you referenced is encountered at a steady state. S-curves won't help you here.
As milldrone suggested, I think going to sensorless vector mode may help here. The drive would then "know " that the load is changing and compensate for the decreased slip. I think.
As far as decreasing the brake voltage, the only thing I would be nervous about are your high mains voltages. If you are seeing 503 VAC for any length of time on your mains, this will increase the operating voltage of your DC bus. I don't know the calculation off the top of my head for determining DC volts based on a three phase voltage, but you would want to make sure that when you have 503 VAC on the mains that your DC bus voltage is still below your braking setting. 760 might be high enough to cover this; but I don't know offhand.
EDIT: DC bus volts = VAC * 1.414 In your case 503 VAC = 711 DC bus, so 760 should work just fine.
Brian