How to minimize voltage drop caused by heavy machine?
We have a typical office environment including computers, scanners, lights, etc. However, we also have a 14" saw. When it starts, the voltage drops for a split of a second. This has no immediate effect except on the scanner. Even though the scanner is plugged into an uninterrupted power supply, if the saw starts and the scanner is in the middle of scanning, the scanner will stop and scanning is aborted. When the saw starts, the uninterrupted power supply produces a click sound. It seems the protection mechanism is kicked in. Why are the computers not affected but only the scanner?
The saw starts roughly every two minutes. This renders the scanner useless. Is there a device I can add to the saw to minimize the voltage drop? Thanks in advance for all the help.
Sounds like you're doing construction. How about a long heavy duty extension cord for the scanner until you get to a circuit not affected by the saw. Or, find a receptacle possibly closer to you for the scanner that is not on the same phase as the saw. (110 volt saw?) That is, which uses a breaker that is on the left half of the breaker box if the saw uses a braker that is on the right half. This assumes you have receptacles on both sides of the breaker box. Check back if you only have lights on the other side. I don't know how big your building is or how many boxes there are.
Or put the saw on a long heavy duty extension cord, but that's my second choice because the saw must use a lot more power and might be impeded by a long extension cord. (Although I have my lawn mower on a 100' foot heavy duty (but I forget what gauge) extension cord, which is plugged into an 8 foot light duty extension cord, and I have no problem. (well it mows the grass well.)
That's a very significant voltage drop. I'd start by making sure you have a large enough cable feeding that saw. If possible, move the saw so it's wired right near the main service entrance (breaker box).
If that dont fix the problem, (If the saw is 120V), wure it to the opposite leg of the system on a 240V system.
If course we dont know if you might have 3 phase wiring, or if the saw's motor is 120 or 240 volts. If that motor is 120v, it might be worth the cost to change it to a 240V motor, which will run more efficiently. Also, could that motor possibly be failing, or have a weak capacitor? A draw that heavy might mean that motor is a little undersize too.
It's real hard to say whats causing this without seeing all the components and wiring layout.
Before you invest any significant money in this, call your power company to inspect the pole transformer and all wiring up on the pole. The transformer might be too small. They should have a number to identify their rating, for example a home may have a 10KVA or 15KVA transformer. But there could be multiple houses /buildings on that same transformer. Yours could just be too small or feeding too many other buildings. There could also be a loose connection up at the pole, or the cables to your building, at the meter, or in your breaker box. All of that should be checked. Maybe the service entrance is too small for your needs.
I'd begin with the call to the power company to check the pole transformer. They are required to do that all the way to your elec meter. All wirring AFTER the meter is your responsibility to check or hire an electrician to do it. But if you show the power company the problem, they might take a look at your system and maybe suggest something, if it's not just needing a bigger transformer.
Here is a little thing I ran across some years ago. A local auto service garage had a very large air compressor. At the rear of the garage was a restroom. More than once, while waiting to have some work done on my car, I'd go in that restroom, and notice the incandescent lightbulb get real dim when the compressor kicked on.
One day I go in there and see he changed the bulb to a CFL. The compressor started and the CFL shut off entirely for a few seconds. I said to the owner, "what's with that light in your restroom". He said it's always that way when the compressor kicks on, and he's had several of those CFLs burn out after only a few weeks.
The next time I went there, he had an incandescent bulb in there again. (I think those surges just killed those CFLs).
A couple years ago, they got a new compressor. He said the old one just died one day and it was time for a new one. The new one is as big if not a little bigger than the old one. Ever since that new compressor was installed, I no longer notice the restroom bulb get dim when the comp. kicks on. I dont know if any wiring was changed when the new compressor was installed, but that light dimming has now stopped. Maybe that motor was failing or under rated, or it could be bad wiring or other things.....
What you explain is probably shortening the life of all your computers too.
What happens if you were to remnove that uninterrupted power supply, and run the scanner directly? Maybe that uninterrupted power supply is weak too. Either way, you have a problem which could damage all your sensitive electronics. I'd not leave it like that very long.
BTW: Have you connected a volt meter to that scanner outlet and watched what the voltage dropped to when he saw kicked on? Most places have between 115 and 120 volts during normal use. But I've seen readings as low as 110 and high as 124. Still fairly normal. If you see a drop below 110, you have a problem....
I don't understand this at all. The purpose of a UPS is to prevent that from happening. You need a better ups...or maybe the batteries are just weak and not really doing their thing.
Maybe you can put the scanner and the saw on different circuits? Depending on the wiring of the building that may or may not help.
Having your ups restart every two minutes sounds like "asking for trouble!"
I don't understand it either. A computer, monitor, and the scanner are plugged into the same power strip which, in turn, is plugged into a UPS. I don't know why the computer is not affected. Perhaps it has something to do with the power supply of the computer.
I'll try piggybacking one UPS to another to see if that helps.
This is 220 V. The transformer is 100 KVA, 3 phase. It feeds one office, one warehouse, and one office/shop which is where I reside. The office has lights, computers, A/C, etc. No heavy machine. The warehouse has mainly lights. There are only two cables coming to this office/shop. Thus, it can only be single phase. There are two breaker panels wired in parallel. I have tried putting the saw to the other breaker panel (two are 10 meters away) to no avail. I guess this is what is expected for parallel panels.
Although the power is supposed to be 220 V, the needle on a refrigerator safeguard points to something like 210V. When the saw starts, the voltage may drop to something like 170 or 180 V (difficult to tell by a needle.)
This is a new saw, about one month old. I hope the motor is not failing.
We have a 30 KVA generator dedicated to our building only. Next time when it runs, I'll watch closely to see if the voltage drop happens again. If it won't happen, I can be quite sure the incoming power lines is the culprit. If it happens again, I don't know what to do next. Would changing the saw cable to a bigger one (smaller gauge number) help? I have no clue.
Same breaker panel but not same breaker. I have tried plugging the saw to another breaker panel to no avail. The two breaker panels are parallel, not serial.
Seems like that should be adaquate for the transformer and wiring.
I'm not sure how that refrigerator setup is wired, but if it's reading the voltage directly off the source wires, you have a BIG PROBLEM. You're dropping nearly 50V below the required voltage.
Now take a plain multimeter, set it to AC Volts, 250V or higher scale. Then SAFELY measure the voltage at the mains. If you're not comfortable doing this, find someone who is or call an electrician.
An electrician will have equipment to measure current draw too, which would be helpful.
Anything is possible, but ot's less likely with a new saw.
Shuting off the GRID power and running the generator would be a good way to check to see if the same problems occur. If not, then you know there is a problem with the power source from the GRID.
I think you have a bigger problem than the saw cable. Too small of a cable would starve the saw motor, leading to eventual motor damage. It should not drop voltage in th building by 50v.
BVut just to know, what is the amperage of that saw? What gauge is the cable (cord). How long is the cord? Are you using an extension cord? (what gauge is the ext cord if you have one). What size breaker is feeding that saw?
Besides what I already said, the NEXT thing you should do is call your power company. After all, part of the reason you pay them, is to maintain PROPER power for your needs. They should not charge you to do an equipment check. Maybe you have everything on one leg of the 3 phase and the other two are sitting idle???? (Unbalanced load).
One other thought. You have that 30KVA generator. There has to be a switching device that completely isolates the generator from the GRID. (REQUIRED by code to prevent backfeeding into the GRID.)
There could be some sort of problem with that switching device.....
Well, the 1st thing I'd try is to plug the scanner directly into the power and not through the UPS. Most UPSs actually switch the output from the mains to the inverter built inside. Some UPSs actually run the load on the inverter all the time. This would probably be good in you case, however, those UPSs are getting fewer and farther between. Computer power supplies tend to have enough storage to hold during the switchover, however, most scanners use a small wall wart power supply and may not have enough capacitance to hold over during the switchover. If that doesn't work, I'd try replacing the wall wart. Some are switching power supplies (more are going this way now) and some are analog. That probably doesn't make a difference as it's all in how much capacitance (holdover capability) it has. So, if the plug to the scanner is a generic plug, changing the wall wart should be easy.
It sounds like the UPS is no good. If it can't handle a voltage drop, what's it going to do with a power loss, etc? First thing I'd do is just try plugging the scanner in directly, no UPS and see what happens. It's possible the UPS senses the power drop, then screws up in the response. The scanner might tolerate the momentary drop in voltage. IDK why you need a UPS on a scanner anyway.
Aside from that, some investigation into the sizing of the conductors, what circuits loads are on, what the root cause is, would be worthwhile too.
It may or may not be the incoming lines. I'd say though, that wiring at some point is not up to the job as you are trying to suck a lot of juice through a small straw. It could be the lines to the panels. I've seen similar situations when a power tool is on too small of a line even though there was plenty of power coming to the panel from the stret. Moving things around to distribute the load properly and assuring the individual lines are adequate is the way to start. If you are not familiar with tracing loads, get an electrician and he can do it for you.
*You may be able to change the taps on the transformer to boost the voltage. There should be a wiring diagram on the inside or outside of the transformer. Power would have to be shut off to the entire transformer to make the change.
We rent this place. Power cables go from the transformer to landlord's office building. Everything has to go through the landlord. Anyway, last week an electrician came, checked the system, and claimed the system has no problems. There is nothing he can do. Well, I don't know how much I can trust the electrician. The government (Burma) doesn't have electric code and doesn't issue licenses for electricians. Virtually anyone can be an electrician.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.