PLC Power Dips!

Dear all,

I now experience machine shutdown due to power dips. You may refer to my previous thread that lead me to power dips troubleshooting.
http://www.plctalk.net/qanda/showthread.php?p=284987#post284987

The machine system stop for a few second and recover a moment later. The PLC turn off during the spike so the Evaporator system just stop. The system resume once the PLC power up again.

I dont understand what is the cause for 230VAC to have power dip. What is the best action to prevend this?

Is there UPS for PLC? What about the 24VDC Power supply?

Yes there are UPS for 24VDC.
For example Siemens Sitop 6EP1-931-... series with external battery.

If you need to counter spikes/noise on the AC side, then an AC UPS or a "voltage stabilizer" may be the correct remedy.

we use a allen bradley cat # 1609-U500N modle # RW 500DR120 volt uniteruptible power suply on out oven flex logix plc's and computers that monitor them due to power issues between storms & power grid issues at my plant in kansas and they have been working great for us. i would thimk that they would have a vertion that would work for you.

Much hate for AC UPS's. I still use some, but am really starting to dislike them.

We've gone to using 24VDC for all PLC power supplies, and control circuits, and use either the Siemens battery module above, or one from AD here:
http://web1.automationdirect.com/adc/Overview/Catalog/Power_Products_(Electrical)/DC_Power_Supplies/RHINO_Metal_Slim-Line_Case

culprit may be present

I have recently experienced power dip in a plant that would cause a Powertec DC drive to fault out. Tracked this problem to a Grinder start up. 100 HP motor on the grinder pulls the voltage momentarily low (-10%) during start up. I am in process of installing a soft start to facilitate ramped up start up. This will hopefully help.
You may want to look for a similar culprit in your facility.

Meh - I'm going to drive 3 hundred kilometers tomorrow to install one on a ship's alarmpanel that I made a couple of years ago, even though it has 2 seperate powersources, that has always kept the plc + sceens up through powerloses. All just cause DNV (a ship insurance company) says so. :angr:

Much hate for AC UPS's. I still use some, but am really starting to dislike them.

We've gone to using 24VDC for all PLC power supplies, and control circuits, and use either the Siemens battery module above, or one from AD here:
http://web1.automationdirect.com/adc/Overview/Catalog/Power_Products_(Electrical)/DC_Power_Supplies/RHINO_Metal_Slim-Line_Case

Click to expand...

I did not know that AD had DC UPS's that's a great find. What do you use for your AC UPS's?

Hook up the plotter on the main line. You may have a motor going bad or an overloaded MCC. You stated that it is 230VAC, is that the voltage on your plants main line? Something has changed and it is drawing down your line voltage. We currently use Liebert power supplies on the PLC's and HMI's and APC smart ups on the HMI servers. In the past I have added line reactors to help with this problem. Keep in mind, the problem could be outside the plant walls!

CharlesM said:

I did not know that AD had DC UPS's that's a great find. What do you use for your AC UPS's?

Click to expand...

For AC UPS's, I've found the Eaton Powerware/Ferrups series to be the absolute most reliable and trouble free. Not inexpensive, but they do work.

http://www.powerware.com/UPS/Ferrups_UPS.asp

All other brands we have tried have failed, or caused other problems, usually in less than a year.

Dear all,

Thank you for your experience sharing and advices.
Now I am installing UPS for the PLC and the Versa View PC.
Hopefully this will prevent the PLC and Versa View to reboot by itself.

I do have this question on the power dips. I wanted find out the bottleneck that cause the power dip.
Hook up the plotter on the main line. 1)You may have a motor going bad or an overloaded MCC. You stated that it is 2)230VAC, is that the voltage on your plants main line? 3) Something has changed and it is drawing down your line voltage. We currently use Liebert power supplies on the PLC's and HMI's and APC smart ups on the HMI servers. In the past I have added line reactors to help with this problem. Keep in mind, 4)the problem could be outside the plant walls!

1) A bad motor and overload would only trip the MCB. Is there a possiblity where these scenario cause power dip to the MCB?

2) 230Vac is the standard voltage appliance in Singapore. For this panel, the incoming Power Supply is 3 phase 400V. It used a step down transformer for 230Vac application, such as PLC and Versa View. (Please refer to my zip file circuit)

3) Yes. We previously installed 1 steam valve and 2 proximity sensors. These devices do not draw much voltage. Our Vendor in Germany design this additional circuit, and the system running a few months before the incidents happened this week.
- Please advice the best way to check overdraw voltage?

4) If this is the possibility, why does it affect our evaporator system instead of all the machines in the plant?

Thank you all for the advices and sharings.
Best wishes to you all.

I have a MCC with about 15 buckets. It is mostly for motors and one is for a lighting panel. The power for the lighting panel runs through a step down transformer. We run a press that cycles every 4-5 minutes and every time it cycles, the lights in my office dim for a second. I have a APC battery backup that boosts the voltage if it drops below a set limit. The UPS beeps every time the boost function comes on and I hear it about 200 times a day. By hearing it beep I know the power dropped 15% the rated voltage. I put a monitor on the main line and saw that when a hydraulic motor was starting that it was dropping the main line from 480vac to 435vac. We are now in the process of moving some of the load off the MCC to help the problem. I can tell you that if I didn't have the UPS on, my server would shut down.

What do you have in the 20A transformer? Also remember that what ever you do to the primary side effects the secondary.

A bad or overloaded motor can draw more current on startup and cause a strain on the main line voltage. This can show up on other equipment as low voltage.

We use a Fluke power monitor for plant and it works very well for troubleshooting power problems. You can also put a scope and check for grounding problems.

get to a garage buy two batteries put them in series and parrallel to the psu. that will solve your problem. although supplier of psu will say bad practice it is fas. However take care that when power really stops you work safe and stop installation.
on ships (my job) telephone some lights and radio are on batteries.

I'm kind of surprised about all this UPS for PLC due to power dips. I have never put a UPS on a plc. When we have a power dip, the most noticed problem is almost ALL of the machines stop due to the safety circuit falling out. I'm not as worried about the plc because now the machines are e-stopped.

Does anyone else experience this? It doesn't seem to matter on the kind of safety contactor or relay. I have AB, FUJI, Banner, etc and it is not limited to only one kind. If the lights dim so it is noticable, we will be restart machines.