Leakage Current of APC-UPS

[Anonymous user]

Hi guys, do you have any idea what is the Leakage Current APC UPS. like for example SU3000RMI3U or SUA model...Thanks in advance

[BillP]

FYI..

Leakage current is the amount of current that leaks from hot or neutral to ground. All current is theoretically supposed to flow between hot and neutral but reality is that a small amount can leak to ground in any electrical device. The leakage current of a UPS is caused by common mode filtering and surge suppression devices. The leakage current of a standard Smart-UPS is < 5 mA (milliAmps).

hope that helps!

[Anonymous user]

Thank IPaW it helps me a lot.

One more thing if the leakage current above or more than 5mA is their any posibility that it will damage the connected load? or something wrong with the hardware of the UPS?....thanks in advance

[BillP]

here is the additional info I found:

A leakage current below 500 micro-Amps is considered low leakage, and many hospitals will not allow electrical equipment to be installed unless it has a leakage current to ground of less than 500 micro-Amps. UL 544 is the UL standard for "Professional Medical and Dental Equipment", and the UL 544 standard requires, among other things, that the leakage current of the device does not exceed 500 microAmps. Another UL standard that is related to medical equipment is UL 2601-1. UL 2601-1 is the UL standard applicable to "Medical Electrical Equipment, Part 1". UL 1778, which is the standard for "Uninterruptilbe Power Supply Equipment", requires that the leakage current of the device does not exceed 5 milliAmps.

APC does not manufacture medical equipment. It is important to understand that, by itself, the UPS cannot reduce the leakage currents of the connected loads. Where the cumulative leakage currents of the loads cause facility GFCIs to trip, adding the UPS will not solve the problem. In such cases, an appropriately sized and UL Listed isolation transformer is required in addition to the UPS.

[Anonymous user]

so you the more the Y capacitor the lesser the leakage current? just to check with you, the Y capacitor is connected at the output of the UPS L-G? thanks inadvance

[Anonymous user]

thank's for the info IPaW...

[Anonymous user]

I've measure the leakage current of my two back-UPS units and both of them show reading of about 1mA or less. The leakage current of these units is bigger than of a typical computer PSU since these UPSses come with 4 "Y" filter capacitores, all referenced to the ground wire. Computer PSU usually come with only two "Y" capacitors. The "Y" capacitors are small blue discs, very similar to varistors, they are put there to filter incoming and outgoing electrical noises.

Message was edited by: rau

[Anonymous user]

No, it's the opposite! The more the Y capacitores installed, the bigger the leakage will be.

The Y capacitors are always installed at the input stage of UPSes, PSUs and some surge protectors. I'm against installing it in surge protectors cause most if not all PSUs today come with Y capacitores so it wouldn't make a difference putting it inside surge protectors. APC Surge Protectors do not come with Y capacitors, at least not the ones I've looked inside.

MOVs installed across the ground wire can also leak some current when they're reaching the end of its life. There are some schools of thought that do not recommend installing MOVs between phase ground and neutral ground for a number of reasons.

Message was edited by: rau

[Anonymous user]

just a curious person i try to open one of our faulty ups, and i saw at the input side there a capacitor and coil, but the capacitor came with the making, i didn't see any "Y" level instead i saw a X-X1... so is these what you reffering to?

[Anonymous user]

The input filter "network" of UPSes usually come with varistors, coils, X and Y rated capacitors. The X rated capacitors are usually yellow in color, but can also come in blue or gray color and square shaped, and Y capacitors are almost always small blue discs, almost like varistors, but if you read the date printed on it, you can see something like "Y1" or "Y2" in very small letters.

There can be some UPS units out there that only came out with a diferential or normal mode filter which comprises of one or more X rated capacitors and one or more coils and nothing referenced to ground.

[Anonymous user]

ok so basically this Y capacitor the cause of leakage current of the ups, what if, if we going to removed the Y capacitor does will affect the performance of the UPS? since the ground conductor is already connected at the body.

[Anonymous user]

Removing these capacitors from the UPS, in my opinion, would not be a big problem since most PSUs come with the same capacitors inside of them. These capacitors are made for filtering EMI and RFI coming in from the utility and other equipments and coming out of switched mode power supplies. Removing it from the UPS wouldn't make much difference regarding the UPS itself. One thing I'm not really sure is if UPSes tend to send out interfences that would interfere with other equipments on the same electrical installation that would be filtered by these Y capacitors. I made one test here though. I isolated the ground prong of my UPS and turned on everything, NO interference whatsoever on my TV, Stereo...

I have just found this on google. Leakage Current Basic Measurements:

http://www.contractor-books.com/Fluke/data/CurrentLeakageBasics.pdf

Message was edited by: rau

[Anonymous user]

You're 100% correct!

I didn't take into consideration the fact that the UPS itself can ouput some noise, I had based my statements on a few basic tests...

If Y capacitors are making GFCIs to trip, measure the leakage current of the UPS, if the problem is found in the UPS, then fix it.

If the amount of devices you have are causing GFCIs to trip, maybe the sum of all Y capacitors leakage is causing this. One of the solutions is to spread the UPSes and other devices among diferent circuits and differents GFCIs or buy devices that have a low leakage current. I don't know the sensitivity of GFCIs in the US, but in Europe and here in my country, they're at least 30mA and can trip from 50-100% of the total 30mA rate, which means it can trip if a 15mA leakage happens.

Message was edited by: rau

[BillP · Accepted solution]

Removing the "Y" capacitors from any product is a bad idea. These capacitors are part of the input EMI/RFI filter circuit which is really a bidirectional filter. While they do and can filter incoming noise, their primary function is to prevent any unwanted conducted interefence from the product itself. They are also critical to the product EMI/RFI/EMC regulatory compliance.

Another issue is the legal implications of user modifications to any equipment. Most manufacturer's icluding APC explicitly prohibit user modifications in their warranties. That is, the warranty is only valid for the product as manufactured by the original manufacturer. By modifying the product you also assume legal liability for any consequential damages that result from the modification.

f. ex. You buy your son a go-cart which has a speed limiter/governor. He complains that it's not fast enough, so you modify the go-cart to allow it to operate at speeds that are in excess of what the manufacturer intended. Subsequently he hit's a tree and is killed. Investigation reveals that the go-cart was traveling at rate of speed that was beyond it's intended design and that it had been modified by you. Who is liabel?

The same thing is true of any product, including UPS units. If you modify or misuse the product and someone is hurt/killed or there is a fire, who is legally liabel for the consequences?

Re. APC UPS leakage current. If you suspect through testing* or discussion with APC technical support that the leakage current on the UPS input supply equipment grounding conductor (PE) of the line cord is in excess of 5ma or 0.005A the product should be returned to APC for testing and/or repairs.

* This test should be done without any connected load equipment and with an instrument capable of +/- 5 % accuracy at 5ma.

Breaking or interrupting the UPS input line cord equipment grounding path (green wire/ground prong/PE) path doesn't remove the "Y" capacitors or change their primary functionality in limiting conducted or radiated interference from the UPS. This is also a very bad idea under any circumstance, because it compomises the life safety of the product. Would you cut the brake lines on your car and then drive it?