Small VFD Issue

[StarCat]

Jraef I could really use your input on this one.
Contact me at ********* if you have a chance.

I am dealing with a lockout matter on a Genesis Drive as made by KB Electronics, model KBDA-29 1P.
The usage is a 3 H,P 3 phase pump being driven on a CIP application.
I brought that unit on line in July and only recently did the drive start giving problems.
This pump does not get much use, only about every 2 weeks or so.
The fault is noted as LU-r [low voltage recovery] and is only supposed to happen under a low line voltage scenario.
The drive was returned to KB Electronics and they did tell me that they were also getting this fault on their bench test.
The only thing they did was to reload the program and send it back after their final test.
I get it back and same thing.
I set a Fluke 87 on the input terminals to the drive and recorded voltage on what would have been an all night run.
I ran the drive for 2 hours without trips before I left.
IN the morning I found the drived locked out on low voltage with the lowest recorded voltage on my meter being 205V on a 208V system.
All connections back to the main have been verified and I don't feel we are dealing with a power problem, although our power is known to be dirty.
I don't think we are dealing with SAGs below the trip point of the drive as the cause.
One of the Techs at KB said something about that model having some moisture sensitivity and that they developed a fix, but the other people at KB have been clueless about this when asked to relate it which is also a bit strange.
Any guidance is helpful.
I am currently going round with the MFG.

(I removed your email from the posting, spammers mine for that sort of thing and we don't want to give them cause to clog up our bandwidth thinking there might be more to find)

 

[Jraef]

For the benefit of others who might need to learn, I'll just answer you here.

One possibility, if you say you have "dirty" power, is that you might have ringing transients that are causing this. The diodes on the font end of a drive rectify the AC to DC by conducting in only one direction. But all diodes have what is called a "Forward Conduction Voltage" (FCV) threshold, meaning that diodes don't always conduct, they don't conduct at ALL until after the voltage sine wave ahead of them gets to the FCV, then they conduct everything asked of them, then STOP conducting again when the sine wave drops again below the FCV. This is what makes the current draw through a diode bridge rectifier be referred to as "non-linear", because the current is drawn in "gulps" at only the peaks of each sine wave. it's this gulping power draw by the way that causes harmonic distortion. This is a crude drawing of the point.


If you have ringing transients on the incoming line that make the sine wave dip below the FCV, the diodes may not conduct for that cycle or less of those cycles. Enough of those in a row, like from some nasty piece of old equipment that runs sporadically, and so many diodes don't fully conduct that the DC bus voltage drops and the drive trips. But also, a side problem is that even if it is just one or two cycles of not conducting, AND the motor is running, then the capacitors discharge into the transistors for the motor, so on the NEXT good cycle from the line source, re-charge themselves instantly. Unfortunately, they do that AT THE AVAILABLE FAULT CURRENT! So you can get hundreds of amps trying to squeeze through the diodes after a transient, and marginally sized diodes can be damaged. This might be why the fault is called "Low Voltage RECOVERY", because KB has decided, rather than beefing up their diode selection, to immediately turn off the drive so that the transistors don't suck power out of the caps and they don't have to recover.

This is why it's a good idea to use line reactors ahead of VFDs if the line source capacity is more than 10x the kVA rating of the drive. A line reactor adds impedance via inductance, so it slows down the rise-time, and fall time, of line transients by virtue of what's called the "Inductive Time Constant", which means that voltage and current cannot change instantly in an inductive circuit. Doing so slows down the ringing transient, avoiding this situation. So my recommendation is, get an inexpensive little 3% line reactor ahead of this drive, you might find that it "cures" this problem.

Alternatively, you could run around trying to find whatever is causing the transients, but that's tough to do. Old DC drives were guilty of this, as are big power supplies, defective ballasts, Y-Delta starters, things like that. The problem is it might not be in YOUR facility. I had one like this that was taking out a lot of Siemens drives on a printing press, same time every year, seemingly random otherwise. Turned out it was a cherry processing plant next door that only ran in season, and they had a big 300HP chiller that was starting with a Y-Delta starter. Every time it started, a VFD in the printing machine died. We found it by accident because we were out in the parking lot after replacing a drive, we heard this chiller start, then a guy ran out to us telling us another drive died!

 

[StarCat]

Jraef, Excellent treatise and much appreciated.
You are Golden.

Warren

 

[StarCat]

Additional Quick Question

Additional Quick Question

On the line reactor I am dealing with a short run from the Sub panel on a dedicated circuit for which only that drive is run on.
It would be preferrable to mount the reactor just downstream of the subpanel rather than right near the point of usage.
Is that acceptable?

 

[GoldDigger]

Since the line reactor is wired in series and there is no source of distortion downstream of the panel either location is fine.
An SPD, on the other hand should be either as close to the source or the load as possible.
If an SPD is protecting a single load putting that parallel device closest to the load takes advantage of the series impedance of the supply wiring to help reduce the surge. That does not apply in the case of s line reactor.

 

[Jraef]

Since the line reactor is wired in series and there is no source of distortion downstream of the panel either location is fine.
An SPD, on the other hand should be either as close to the source or the load as possible.
If an SPD is protecting a single load putting that parallel device closest to the load takes advantage of the series impedance of the supply wiring to help reduce the surge. That does not apply in the case of s line reactor.

Bingo...

 

[StarCat]

Many Thanks

Many Thanks

Bingo...

Gold Digger thanks for the Tech input.
The forum is of the greatest value in such matters.

Sincerely

Warren

 

[StarCat]

Sizing

Sizing

Ok I do not encounter this kind of thing every day so could use guidance on the size which I am getting confusing information on.
I am dealing with a 3 HP motor.
This is the first thing I found after being directed towards a line reactor:
http://www.automationdirect.com/adc..._-a-_Accessories/AC_Line_Reactors/LR-23P0-1PH

Then I am looking at another model that is in a vented enclosure but made for 3 PH input and the Salesman tells me I have to take the FLA of the motor and multiply it by square root of 3 to get the correct size for my duty???? That comes out to something like 17.2A

Please enlighten me on the choice for 3 HP single phase input. I'd like to have one already in an enclosure if possible.

 

[kwired]

Ok I do not encounter this kind of thing every day so could use guidance on the size which I am getting confusing information on.
I am dealing with a 3 HP motor.
This is the first thing I found after being directed towards a line reactor:
http://www.automationdirect.com/adc..._-a-_Accessories/AC_Line_Reactors/LR-23P0-1PH

Then I am looking at another model that is in a vented enclosure but made for 3 PH input and the Salesman tells me I have to take the FLA of the motor and multiply it by square root of 3 to get the correct size for my duty???? That comes out to something like 17.2A

Please enlighten me on the choice for 3 HP single phase input. I'd like to have one already in an enclosure if possible.

Based on what you said here you apparently have single phase instead of three phase input on your drive. The reactor you linked to is for single phase input drives which would be what you need if single phase input.

I don't know how size of the reactor was selected, but keep in mind the current of the single phase side will be 1.73 times higher then the current on the three phase output (assuming same voltage on both sides).

 

[StarCat]

Yes

Yes

Based on what you said here you apparently have single phase instead of three phase input on your drive. The reactor you linked to is for single phase input drives which would be what you need if single phase input.

I don't know how size of the reactor was selected, but keep in mind the current of the single phase side will be 1.73 times higher then the current on the three phase output (assuming same voltage on both sides).

This what was not made clear yesterday when I was iquiring about a 3 ph reactor for single phase input use.
The Drive is a 1PH input 3HP unit.
So what I am getting is as this.

The 3HP single phase unit I linked to will do the job.
If I want to use a 3 phase model which may be desirable due to the integrated case, I will need to use the 1.73 factor for correct sizing due to the load being single phase.

Thanks

 

[jminer99er]

Thank you Jraef, I'm always trying to learn!

 

[Jraef]

This what was not made clear yesterday when I was iquiring about a 3 ph reactor for single phase input use.
The Drive is a 1PH input 3HP unit.
So what I am getting is as this.

The 3HP single phase unit I linked to will do the job.
If I want to use a 3 phase model which may be desirable due to the integrated case, I will need to use the 1.73 factor for correct sizing due to the load being single phase.

Thanks

You got it.

I would go for the 3 phase reactor up sized. By the time you buy a box to house the single phase one, install vents etc, you will likely pay more for the package.

 

[kwired]

I guess I don't see why one would prefer a three phase reactor if only using it for single phase.

The three phase reactor that I am seeing from same site (automation direct) that rated approximately same current level is rated 5 hp three phase and is about $10 higher - did not check if it is different dimensions but guessing it is fairly similar in size.

I guess what I am saying is I don't think it really matters much which one you use they both are going to cost about the same and I doubt performance will be impacted much either way.

 

[Jraef]

I guess I don't see why one would prefer a three phase reactor if only using it for single phase.

The three phase reactor that I am seeing from same site (automation direct) that rated approximately same current level is rated 5 hp three phase and is about $10 higher - did not check if it is different dimensions but guessing it is fairly similar in size.

I guess what I am saying is I don't think it really matters much which one you use they both are going to cost about the same and I doubt performance will be impacted much either way.

Only because he said he can't get the single phase version in an enclosure, so he would have to add the enclosure, vents and his labor to put it together. So if the cost is the same, I would get the one that takes less work. I'm lazy that way.

 

[Ingenieur]

This may be a factor
you have a 3 HP so basically over-loaded by 50 %
have you measured I in and out?
the drive mfg makes line chokes as optional equipment
although imo not your issue, they are usually used to trap THD generated by the inverter switching action

1. Model KBDA-29 – Terminals “L1”, “L2”, “L3” – Designed for single-phase or 3-phase AC line input.Rated for 208/230 Volt AC line input only. Rated for 2 HP maximum with single-phase AC line input(Terminals “L1”, “L2”) and 3 HP maximum with 3-phase AC line input (Terminals “L1”, “L2”, “L3”).

1. Model KBDA-29 – Has a maximum rating of 9.0 Amps (3 HP (2.25 kW)) when used with a 208 – 230Volt 50/60 Hz 3-phase AC line input. When used with a 208 – 230 Volt 50/60 Hz single-phase AC lineinput, the maximum rating of the drive is 6.7 Amps (2 HP (1.5 kW)). Be sure to reprogram MotorCurrent (Function No. 0.01) to the actual motor nameplate current rating (not to exceed 6.7 Amps)
   

 

[Ingenieur]

Your code means uv trip and returned to nml
uv is 151 vac on that drive

try setting the ride through time to 2 sec max group 1.06
and auto restart after return to nml group 1.05 setting 002
on some drives you can select the number of tries

 

[kwired]

Only because he said he can't get the single phase version in an enclosure, so he would have to add the enclosure, vents and his labor to put it together. So if the cost is the same, I would get the one that takes less work. I'm lazy that way.

Maybe I'm missing something, but if he is getting one from AD like the one he linked to - none of them come in an enclosure that I am aware of.

 

[Jraef]

Maybe I'm missing something, but if he is getting one from AD like the one he linked to - none of them come in an enclosure that I am aware of.

Here's what he said (to make it easier since we have a new page);

This is the first thing I found after being directed towards a line reactor:
http://www.automationdirect.com/adc/...rs/LR-23P0-1PH

Then I am looking at another model that is in a vented enclosure but made for 3 PH input and the Salesman tells me I have to take the FLA of the motor and multiply it by square root of 3 to get the correct size for my duty???? That comes out to something like 17.2A

That's what made me think he was comparing an open type for single phase, as in the linked image, vs an enclosed version for 3 phase, which from what I know of reactors is going to be cheaper than assembling it himself..

 

[kwired]

Here's what he said (to make it easier since we have a new page);



That's what made me think he was comparing an open type for single phase, as in the linked image, vs an enclosed version for 3 phase, which from what I know of reactors is going to be cheaper than assembling it himself..

I understand, his source for the one in a ventilated enclosure must have been somewhere other then AD, and they must not have had one available with single phase reactor installed.

My confusion was when he linked to the AD model, all they have AFAIK is open units and you have to put them in your own enclosure.

 

[Ingenieur]

The motor FLA 17.2 /sqrt 3 = 10 A ??? ( from his choke sizing post )
the drive is only rated for 6.7 output on 1 ph input?

the max S for the drive at 230/3 is sqrt 3 x 230 x 6.7 ~ 2.7 kva
converted to 208/1 is 13 A drive input
call it 15 assuming the pump is fully loaded and some drive loss

if really power quality perhaps a cvt like a sola
will maintain V, isolate THD both ways, reduce line noise, etc
i don't think it is power related, magnitude or quality