Oversize Line reactor

I have two drives that are tripping (F05 Bus Overvolts) intermittently due to spikes on the incoming AC line.

One of them is 1HP and the other is a 2HP drive...both Powerflex 40.

Is there any harm is using a 3% line reactor (for each drive) that is rated for up to 5HP (8 amps)?

Thanks,
Paul

As far as I know that won't be an issue. You are just paying for a little more material than you really need to.

I'm not a power electronics guy but I've never understood how power spikes can cause an overvoltage trip on a device with enough bus capacitance to maintain it's logic supply for 15 seconds after the power is disconnected. A voltage spike is the electronic equivalent of a 1-second blast from a pressure washer into a bathtub. That certainly wouldn't overflow the bathtub unless the level were right to the rim already. If the overvoltage is the result of a ground plane shift than you will probably need something a little more involved than a line reactor. You would probably want a power filter.

Keith

If they're in the same cabinet, you might be able to use one reactor for both drives. You would have to check the total input amps of the drives to see if they're under the rating of your reactor. Or is your goal to isolate them from the line, as well as each other?

-rpoet

kamenges said:

. . .I've never understood how power spikes can cause an overvoltage trip on a device with enough bus capacitance to maintain it's logic supply for 15 seconds after the power is disconnected. A voltage spike is the electronic equivalent of a 1-second blast from a pressure washer into a bathtub. That certainly wouldn't overflow the bathtub unless the level were right to the rim already. If the overvoltage is the result of a ground plane shift than you will probably need something a little more involved than a line reactor. You would probably want a power filter.

Keith

Click to expand...

The tech at a/b said that the voltage spike might only be microseconds in duration (too fast for my meter to catch) since the first thing it hits is a rectifier which instantly turns it into DC voltage and applies it to the bus. I am with you, though, that the bus should immediately drop that voltage down to an acceptable level. The PF40 book says that the fault level for high DC bus is 810vdc which equates to a line voltage of 575vac. I can't think of what we have that might cause that sort of noise...although there are two old 1336 drives on this same MCC center that don't have line reactors and also never fault for bus volts...

He recommended line reactors as a solution.

I have ruled out all the load size causes. I tried a longer decel time (3.0 seconds) for 24 hours but it did not help. Today, I set the decel rate to 0.5 seconds and tried over 20 times to make the drive fault. I tried short cycles, long cycles...the PLC limits the short cycles (drive must stop for 5 seconds before it can start again in either direction).

Sometimes the drive trips when sitting enabled with no run command (stopped). I left my Fluke on peak hold for 2 hours and the range it picked up was 439 to 459.9 vac, even though the drive fault queue shows that it tripped for high DC Bus volts once during that test.

I can't use one reactor for both drives, since they're installed in MCC buckets and drive equipment located on opposite sides of a production floor.

I still haven't found the line reactors we are supposed to have on the shelf, so if I have to order some, I will try not to oversize them, but it would be nice to stock as few as possible, since the cost difference between a 1hp and a 5hp is only a few dollars.

Okie, since AB has chosen not to put any reactance in its input leads, you will have very nervous units. You are right that this is input power noise since it happens when the drives are not running the motors.

These little drives actually don't have that much capacitance on the bus compared to the energy these little power pulses contain. I would choose 5% reactors as long as your voltage isn't any lower that 470VAC. If its lower than that, you can't afford to put much reactance in since it will lower the voltage further at full speed and full load. Better limit to 3% if that's the case.

These reactors may very well not fix your problem. But they are a necessary step to what comes next. I believe the PF40's have built-in brake choppers so I would add a brake resistor. That in combination with the line reactor will probably swamp the energy. You might even try the brake resistors first since they are cheap.

These drives...[shaking head]

Input voltage rating is "380-460vac" or "380-480vac" depnding on which piece of the literature library you're lost in.

My plant voltage as captured by the peak hold function on my Fluke (110 I think) meter revealed 439 to 459.9 vac with an average of 457. I don't recall the specs of my meter, but I am sure the minimum time to record a peak is much longer than a couple ms. My meter hung on the bucket door for 1.5 hours while I did other work, and the drive fault buffer had a new entry (I cleared it first setting A100=2) for F05.

The 5HP line reactors I can get from AutomationDirect.com overnight are 25w heaters and had a different mH value than the 1-2hp model which they're sold out of at the moment.

I found one 22amp Hammond Electric 3 phase reactor I think its for a 15HP 3% reactor. I guess we used up all the little ones.

Anywho, I don't want any more heaters in the panel and I cant tie them together so I am going to order enclosed reactors and mount them on top of the MCC center.

I am going to find two 2HP reactors tomorrow for the input.

Thanks for giving your input on this, Dick.

So, If I did have two reactors sized for 5hp @ 3%, could I have put a 1HP drive on it safely?

And, with my voltage values:
Supply avg.=457
Drive rating 360-480?
DC Bus Hi tolerance=810vdc
DC Bus Lo tolerance=??? (I am at home with CRS syndrome)

Thanks everyone for your input.
Paul

These drives...[shaking head]

Input voltage rating is "380-460vac" or "380-480vac" depnding on which piece of the literature library you're lost in.

My plant voltage as captured by the peak hold function on my Fluke (110 I think) meter revealed 439 to 459.9 vac with an average of 457. I don't recall the specs of my meter, but I am sure the minimum time to record a peak is much longer than a couple ms. My meter hung on the bucket door for 1.5 hours while I did other work, and the drive fault buffer had a new entry (I cleared it first setting A100=2) for F05.

The 5HP line reactors I can get from AutomationDirect.com overnight are 25w heaters and had a different mH value than the 1-2hp model which they're sold out of at the moment.

I found one 22amp Hammond Electric 3 phase reactor I think its for a 15HP 3% reactor. I guess we used up all the little ones.

Anywho, I don't want any more heaters in the panel and I cant tie them together so I am going to order enclosed reactors and mount them on top of the MCC center.

I am going to find two 2HP reactors tomorrow for the input.

Thanks for giving your input on this, Dick.

So, If I did have two reactors sized for 5hp @ 3%, could I have put a 1HP drive on it safely?

And, with my voltage values:
Supply avg.=457
Drive rating 360-480?
DC Bus Hi tolerance=810vdc
DC Bus Lo tolerance=??? (I am at home with CRS syndrome)

Thanks everyone for your input.
Paul

Two things here, OkiePC. First, its the mh inductance that really determines the reactor's ability to filter. I think you'll find that a 3% 1hp reactor will have much more inductance that a 3% 5hp reactor so the 1hp reactor will be a better filter at low currents than the 5hp unit. Second, at 459V on your power supply, you really can't afford to drop an additional 3 to 5% of the supply voltage ahead of the drive. After all, a 3% reactor will drop 13.5VAC at rated current (459 x .03 = 13.5). That drops the input voltage to 459-13.5 = 445.5V. That will limit the drive output voltage to 445V as well so your motor will be voltage-starved above about 55Hz. Not a good thing! I think you might be better off just adding brake resistors and hope they swallow the pulses before the drive trips. Use the minimum ohm resistor AB approves for the specific drive you've got.

Very well then. I will opt for braking resistor circuits instead. I think we have one stashed sized for a 1HP ab160 series drive that I could test with. I will run the numbers tomorrow to see if it's suitable, if not, I'll order a single pole OL relay and the correct resistor for the drives. One good thing about the drive is that it does have a built in braking IGBT.

Thanks again, and I will be sure to follow up with results.

Okie

We have similar issues with some ab drives in specific areas of the plant. We use block products http://www.block-trafo.de/en_US/home/ for input side conditioning and output side.

They have voltage stabilizers http://www.block-trafo.de/en_US/products/power_quality/product/720953/

Line reators http://www.block-trafo.de/en_US/products/power_quality/product/393225/

and power harmonic filters http://www.block-trafo.de/en_US/products/power_quality/product/1572893/

Many other factors come into play when making a selection voltage, feeder length and impedence,load type and size the type of inverter section the drive is using 6,12,or 18 pulse.

They have very good engineers and are a rockwell encompass partner and use their products on ab drives a lot. They have been a lot of help to use many times and their products are top of the line but with decent pricing.

kamenges said:

As far as I know that won't be an issue. You are just paying for a little more material than you really need to.

I'm not a power electronics guy but I've never understood how power spikes can cause an overvoltage trip on a device with enough bus capacitance to maintain it's logic supply for 15 seconds after the power is disconnected. A voltage spike is the electronic equivalent of a 1-second blast from a pressure washer into a bathtub.

Click to expand...

Unless you've got a big damn drive, I think the analogy would be better with a bucket or a glass of water.

DickDV said:

I think you might be better off just adding brake resistors and hope they swallow the pulses before the drive trips. Use the minimum ohm resistor AB approves for the specific drive you've got.

Click to expand...

I would have never thought of this strategy, but it makes a ton of sense now that I'm thinking about it.

Okie - Have you tried throwing your meter on the DC bus of the PF to see what it's peak voltage and average are?

monkeyhead said:

Okie - Have you tried throwing your meter on the DC bus of the PF to see what it's peak voltage and average are?

Click to expand...

And then compare it with what the drive says the DC bus voltage is. On more than one occasion I have had drives that report different voltages than my meter does. And different voltages on side by side units that were connected at the DC buss.

monkeyhead said:

Okie - Have you tried throwing your meter on the DC bus of the PF to see what it's peak voltage and average are?

Click to expand...

Yes, I did that, and the readings were within a couple of volts.

Today, the North drive was going nuts, tripping every hour or so. Normally it would trip three or four times per day. The south drive has only tripped twice in 48 hours.

I noticed while watching it that the output frequency would go to 90Hz for two or three seconds, then ramp down to 20Hz for a couple of seconds, and then go to 70Hz. It would follow this pattern each time the run command was asserted.

There is no way the drive should do anything but ramp to 70Hz, and ramp back to zero. We don't have any step logic inputs programmed, and don't have any of the extra digital inputs wired to anything, and they don't show to be active in the drive status.

So, now that PF40 is in the dumpster and I stuck a 160 series drive in its place. I did that about 10:30, so it's too early to tell if it has helped, but no faults so far.

Thanks for the further info, fellows.

Paul

Originally posted by OkiePC:

I noticed while watching it that the output frequency would go to 90Hz for two or three seconds, then ramp down to 20Hz for a couple of seconds, and then go to 70Hz. It would follow this pattern each time the run command was asserted.

Click to expand...

Now THAT makes alot more sense. Not so much the dancing frequency part but the bus overvoltage part.

Keith

Except I thought you said this was happening with NO run signal asserted!