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  1. #1

    Default Under voltage protection...how much do I need?

    Right now I only have basic surge protector power strips but am looking for something more (ideally also with 12V triggers). I experience a fair amount of voltage sags during the T-storm season when the power grid switches between transformers due to the strikes. I have never measured these but the lights will dim, flicker, cut off then cut on...so not ideal for electronics.

    When looking for protection from under voltage i see products from Panamax that protect from 100V and below and others that don't protect until the voltage drops to 90V.

    This raises the question of where does the voltage drop damage most types of equipment and are either of these points sufficient?

    Thoughts?

    Thx

  2. #2
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    Default Re: Under voltage protection...how much do I need?

    Depends on the PSU.

    Linear PSUs in amps will generate less rail voltage, which doesn't matter much until the audio peaks start to approach the limit, then it clips. You only need to worry if the rails drop low enough that transistor biasing fails. You might end up with some DC on the outputs, but a good amp will protect against those conditions. (Tell-tale sign is relays closing and opening.)

    Most digital electronics will have switch-mode PSUs that vary their duty cycle to generate low voltage rails. There's often quite a bit of headroom, so they may not care until well below nominal voltage. But, if there's a brown-out, with no incoming line voltage, any reserve capacity may be depleted, causing resets or undervoltage conditions that corrupt the code paths or data in the MCUs. So that's not good.

    Modern LCDs will probably fair well enough, but may shut down or reset during the sag. Projectors DO NOT like bad power. You'll damage the bulb and/or high-voltage PSU if proper power-up and power-down sequences aren't followed.

    If you have old-skool linear amps with output protection, don't worry about them. Put all your lower-current devices on a small UPS if you can. Forget undervoltage protection in power strips. They can only shut down the entire load when low voltage is detected, which is arguably no better. Matching transformers can shift taps to compensate, but you're looking at expensive and huge boxes to do this. May as well just get a UPS.

  3. #3
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    Default Re: Under voltage protection...how much do I need?

    Get the largest on-line style UPS your budget will allow. http://www.pcguide.com/ref/power/ext...sOnLine-c.html
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche

    http://www.diy-ny.com/

  4. #4

    Default Re: Under voltage protection...how much do I need?

    Quote Originally Posted by Kooshbal View Post
    Right now I only have basic surge protector power strips but am looking for something more (ideally also with 12V triggers). I experience a fair amount of voltage sags during the T-storm season when the power grid switches between transformers due to the strikes. I have never measured these but the lights will dim, flicker, cut off then cut on...so not ideal for electronics.

    When looking for protection from under voltage i see products from Panamax that protect from 100V and below and others that don't protect until the voltage drops to 90V.

    This raises the question of where does the voltage drop damage most types of equipment and are either of these points sufficient?

    Thoughts?

    Thx
    It depends on the particulars. I've actually never seen anything damaged by too low of a voltage, not that it can't or doesn't happen. Typically the device just doesn't work.

  5. #5

    Default Re: Under voltage protection...how much do I need?

    Quote Originally Posted by Kooshbal View Post
    Right now I only have basic surge protector power strips...
    Be careful in how you make use of surge protectors. All equipments sharing low voltage interconnections should also share very similar ground potential.

    Quoted below is a good article by Bill Whitlock, President of Jensen Transformer, AES Life Fellow, IEEE Life Senior, and expert on the subject matter.

    http://svconline.com/mag/avinstall_s...tionthe_enemy/

    SURGE PROTECTION:the enemy within
    Jul 1, 1999 12:00 PM, Bill Whitlock

    Most people have been convinced that ordinary power lines are teeming with equipment damaging spikes and surges and have, without hesitation, installed a myriad of protective devices they believe will prevent costly system problems. This protection business is a huge, fast-growing industry with lots of players. In researching this column, I found an article urging electric utility companies to get in on the action, "Cooper recommends that the utility lease the meter socket arrester to their customers for several reasons. First, the monthly revenue (often between $4 and $9, depending on location) is a long-term source of income" [ref 1]. All too often, science and reality take a back seat to sales and profits.

    Do not misunderstand-such protection is good, but only if applied thoughtfully. In fact, the meter socket arrester is an excellent idea because it completely avoids the subject problem. The real problem is the haphazard use of common all-mode protectors at AC outlets or outlet strips. In many cases, this practice causes either system noise problems or hardware damage. The noise is heard as pops and clicks in audio systems, seen as specks or sparkles in video systems, or experienced as a crash or lock-up in computer systems. The hardware damage does not usually occur in the power supply, where you would expect it, but in the signal I/O interfaces that connect to the outside world.

    What they are Normal 120 V (RMS) AC power alternates between peak voltages of +170 V and -170 V. Power-line spikes and surges are generally defined as short-term over-voltages with spikes characterized as having higher peak voltages but shorter durations than surges. The vast majority of protective devices use a component, such as a metal oxide varistor (MOV), to limit the peak voltages on power lines by drawing large currents when the voltage attempts to exceed the clamping or let-through level. Most simple suppressors use these devices to divert or shunt the resulting surge current, causing large pulses of current, hundreds or thousands of amperes, to flow in the circuit during the surge.

    Underwriter's Laboratory (UL) has rated surge suppressors for safety per specification UL 1449 for some time, but in 1996, it collaborated with the U.S. government to produce the UL1449 Adjunct Classification performance specification. This spec classifies suppressors in several ways and helps to promote the use of standardized terminology. Mode 1 is defined as line (B or black wire) to neutral (W or white wire), and is also called normal-mode or differential-mode. Mode 2 adds line (B) and neutral (W) to safety ground (G), and is also called all-mode. Surge energy from a lightning strike to the power line, for example, will enter a facility in Mode 1. Note that surge voltage between neutral (W) and safety ground (G or green wire), also called common-mode, cannot exist at the service entry panel because code mandates that these conductors be bonded together as shown in Figure 1. Common-mode surge voltages are coupled from the line (B) to neutral (W) by branch circuit loads, tend to increase with distance from the bond at the service entrance, and are usually much lower in voltage than normal-mode surges [ref 2]. In spite of this, most commercial suppressors are Mode 2, which diverts surge energy from line or neutral to the safety ground. In real-world systems, these suppressors can be a liability-the dumping of surge currents into the safety ground can have dire consequences.

    System level effects Nearly all equipment is grounded, via the third pin on its power cord, to the electrical system's safety ground. For reasons stated in previous columns and other writings, this ground is adequate, safe, and legal; do not defeat it! Therefore, depending on their physical locations and the building's wiring, any two pieces of equipment will have their grounds connected via some length of the building's safety ground wiring. If both devices are plugged into the same outlet, this length will be small, but, if the devices are powered from different branch circuits (breakers) or operate on isolated power (orange outlets with dedicated grounds), the ground wires may be quite long. Most transient over-voltages are high-frequency events, having most of their energy well above 100 kHz. At these frequencies, long wires, regardless of their gauge, have high impedance and will develop extremely high voltage drops when carrying the high current pulses created by MOV clamping. For this reason, the wires connecting the distant protected outlet are shown as inductors L1, L2 and L3 in Figure 1. Figure 1 shows the effects of a 6 kV spike arriving on the incoming utility power on a common computer-to-printer hookup. During the spike, a brief current of perhaps 2,000 amperes will flow in the paths indicated by the solid arrows. Under these high-current conditions, the clamp voltage of the MOVs may rise to about 600 V. Note that about a third of the spike voltage appears across the lengths of the neutral (W) and safety ground (G) wires connecting the protected outlet to the breaker panel. This outlet's ground and the ground of anything plugged into it, jumps to 1,800 V relative to the earth ground at the breaker panel. This voltage is likely to reduce interface circuitry in the computer, printer or both to silicon vapor. More frequent low-voltage spikes (down to the low-current MOV clamp of 300 V or so) will still cause high-current pulses to flow in the same loop. These smaller noise spikes between the grounds will cause errors or lockup. Remember that RS-232 and printer parallel ports are unbalanced and prone to ground noise. In my opinion, a great deal of unexplained computer behavior is caused by this kind of problem, and I am certain it causes many audio and video system noises.

    Surge protection is something that must be designed and implemented methodically. The absolute best place to guard against incoming spikes and surges is at the service entry panel or a sub-panel that powers everything in an interconnected system. Unless your system operates on a branch circuit that is shared with spike-producing loads (air conditioners, refrigerators, light dimmers) this will most often be enough protection for even so-called sensitive loads. If surge suppression must be used at an outlet or outlet strip, do not use ordinary Mode 2 suppressors unless every piece of interconnected equipment is powered from the same protected outlet or strip. From a system noise (and hardware damage) point of view, the best suppressors operate in series mode. Although conventional Mode 1 suppressors may simply consist of an MOV placed across the line, they still cause high spike currents that circulate in wiring. Series type Mode 1 suppressors, however, use inductors to limit and a capacitor bank to absorb high-frequency energy, which is then slowly released into the neutral wire. Such suppressors from New Frontier Electronics (www.surgex.com) have met the highest possible A-1-1 performance and endurance ratings in UL1449 tests.

    1. C. Plummer, Storm Trapper "HSE Residential Lightning Protection Program," The Line On-Line, Cooper Power Systems, April 1997.

    2. F. Martzloff, "The Propagation and Attenuation of Surge Voltages and Surge Currents in Low-Voltage AC Circuits," IEEE Transactions on Power Apparatus and Systems, Vol. PAS-102, May 1983.

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  6. #6
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    Default Re: Under voltage protection...how much do I need?

    Excellent find, and entirely sensible advice. I've never really thought much about how surge protectors work, but that makes perfect sense.

    Incidentally:
    http://www.penny-arcade.com/comic/2002/11/25

  7. #7

    Default Re: Under voltage protection...how much do I need?

    What you need is a decent power line conditioner followed by a decent UPS.

  8. #8
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    Default Re: Under voltage protection...how much do I need?

    Before I started using a UPS lost a few computer parts to low power conditions, brown-outs. The power where I live now is low and probably dirty as the transformer in my Samsung 55" LED hums (sometimes fairly loudly) when I turn it on in the early morning hours. A good UPS and power conditioner is on my list for my AV stuff.

  9. #9
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    Default Re: Under voltage protection...how much do I need?

    If you have a UPS, a power conditioner is a waste of money. If you don't, it probably still is. PSUs filter dirty power by their nature. The only things you have to worry about are gross over and under voltages (which the UPS would cover), and outages (which the UPS will cover).

  10. #10
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    Default Re: Under voltage protection...how much do I need?

    Quote Originally Posted by Tin_Ears View Post
    What you need is a decent power line conditioner followed by a decent UPS.
    Since both generally have some sort of surge protection, plugging one into the other may be a bad idea.

  11. #11

    Default Re: Under voltage protection...how much do I need?

    Quote Originally Posted by Dabspok View Post
    Before I started using a UPS lost a few computer parts to low power conditions, brown-outs. The power where I live now is low and probably dirty as the transformer in my Samsung 55" LED hums (sometimes fairly loudly) when I turn it on in the early morning hours. A good UPS and power conditioner is on my list for my AV stuff.
    I experienced low voltage in a residence where I lived many years ago. I became aware of the problem while watching the VU meter lights on my stereo wax and wane to the beat of the music. I called my local utility company and complained about it after I of course checked the voltage with a meter. Soon after that a utility crew ran new cabling from their pole to my residence, which fixed the problem.

  12. #12

    Default Re: Under voltage protection...how much do I need?

    This is all excellent information, thank you.

    One other thing to add is that I need to have a 12v trigger controlling 1 or 3 outlets so that my amps get switched on with the receiver...do the UPC typically have this feature? Are "smart power strips" safe to plug ito a UPS?

    Thx

  13. #13
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    Default Re: Under voltage protection...how much do I need?

    Quote Originally Posted by SirNickity View Post
    If you have a UPS, a power conditioner is a waste of money. If you don't, it probably still is.
    +1. Audio and video gear power supplies do all the conditioning that is required. Both UPS and conditioners didn't exist before the PC, and they came along to address the problems of early PC power supplies, which were cheap, and in the case of the UPS to allow one time to save their data and shut the PC down safely in the event of a power failure. High current draw devices, such as amplifiers, should not use power conditioners or UPS, as they can be current starved. Where amp manufacturers make any recommendation at all it's against their usage.

  14. #14

    Default Re: Under voltage protection...how much do I need?

    So a good surge suppressor power strip with a 12v trigger should be all that I really need?

  15. #15

    Default Re: Under voltage protection...how much do I need?

    Quote Originally Posted by SirNickity View Post
    If you have a UPS, a power conditioner is a waste of money. If you don't, it probably still is. PSUs filter dirty power by their nature. The only things you have to worry about are gross over and under voltages (which the UPS would cover), and outages (which the UPS will cover).
    Quote Originally Posted by billfitzmaurice View Post
    +1. Audio and video gear power supplies do all the conditioning that is required. Both UPS and conditioners didn't exist before the PC, and they came along to address the problems of early PC power supplies, which were cheap, and in the case of the UPS to allow one time to save their data and shut the PC down safely in the event of a power failure. High current draw devices, such as amplifiers, should not use power conditioners or UPS, as they can be current starved. Where amp manufacturers make any recommendation at all it's against their usage.
    Tell that to my two computers with blown motherboards when they weren't plugged into line conditioners. And gross over/under voltage is precisely what destroys electronics. I think we're on the same sheet of music... just playing in different keys.

  16. #16
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    Default Re: Under voltage protection...how much do I need?

    Quote Originally Posted by billfitzmaurice View Post
    High current draw devices, such as amplifiers, should not use power conditioners or UPS, as they can be current starved.
    In pro audio applications and larger home installations that use multiple high power amplifiers having a UPS that can supply enough current to support these devices is very cost prohibitive.. could cost more than the audio gear itself. But for your typical HT with an all-in-one AVR a whole system UPS is entirely feasable and a good idea. For example I have an APC 1300VA UPS protecting my HT which consists of a 6.1 AVR, CD changer, DVD player, HD cable box and 42" plasma TV. The only thing not on full UPS support in this system is a 12" powered sub but it's still routed through the units surge protection. This unit has successfully protected this system for several years now and even provides ~10 min of operation during a power failure.. at low output levels obviously. Before buying the UPS I lost the AVR to a power spike/brownout resulting from an electrical storm and the system wasn't even in use at the time, I have had no loses since.
    Paul O

  17. #17
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    Default Re: Under voltage protection...how much do I need?

    Here are a couple things to consider, both pro and con to filtering.

    - Unless you put out BIG bucks on the UPS, it's not running off batteries unless the AC power is out-of-spec enough to trigger the switch to protected power. (These are the so-called "online" UPSes, and they're not the majority by a long stretch.) So, when your UPS is not providing battery backup, you're essentially running through a surge protector.

    - Any device that plugs into any other device (computer to printer, receiver to TV, etc...) is limited to the protection of the least-protected device. If you isolate your SACD player, then use RCA cables to plug that into your pre-amp, then into your amp, you have provided a path for noise and spikes to invade your SACD player despite your protection. And now it's going through low-current input/output stages. So unless you're prepared to buy enough filtering or isolating capacity to filter EVERYthing that plugs into anything else, extensive protection is dubious at best, harmful at worst.

    - Don't forget your cable TV coax, phone lines, antennas, etc... Proper service entry grounding and spike arrestors in-line will help.

    - Having any sort of filtering that dumps noise or spikes from the line to neutral or ground is going to have the effects listed, again, in that AES post above. The only fix is to have all interconnected devices behind this protection. Having service entry protection is a great idea that I hadn't thought much about before, but it makes all kinds of sense given common-sense knowledge of grounding best practices. Having all connected devices on one branch circuit, and protecting that circuit, is second best. Anything else is subject to non-zero volt ground references.

    - Equipment PSUs already use at least filtering capacitors, and in the case of LV sensitive electronics, also inductors, and probably another stage of capacitors. These shunt and resist noise and spikes using the same techniques that power filtering devices do.

    - If you fry a device powered by a quality surge protector, it probably wasn't the power input that killed it. See above. Trace its connections to other devices and see where there may have been differences in ground levels, because that's probably the cause of death.

  18. #18
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    Default Re: Under voltage protection...how much do I need?

    Quote Originally Posted by Tin_Ears View Post
    Tell that to my two computers with blown motherboards when they weren't plugged into line conditioners. And gross over/under voltage is precisely what destroys electronics. I think we're on the same sheet of music... just playing in different keys.
    Did you read my post? Both UPS and conditioners didn't exist before the PC, and they came along to address the problems of early PC power supplies, which were cheap, and in the case of the UPS to allow one time to save their data and shut the PC down safely in the event of a power failure. Computer power supplies just aren't made very well. Better today than they used to be, but still not great. AV gear makers do a lot better job with their power supplies.
    I haven't had a single piece of gear damaged by any power issues, both in my home and my professional gear, going back to 1965. I had one piece of gear damaged when the house we were practicing in took a direct lightning hit. I had left a mic cable, sans mic, plugged into one channel, the connector on the concrete floor of the basement we were in. The hit fried the op amp on that channel, the cost to repair was five bucks.

  19. #19

    Default Re: Under voltage protection...how much do I need?

    Quote Originally Posted by billfitzmaurice View Post
    Did you read my post? Both UPS and conditioners didn't exist before the PC, and they came along to address the problems of early PC power supplies, which were cheap, and in the case of the UPS to allow one time to save their data and shut the PC down safely in the event of a power failure. Computer power supplies just aren't made very well. Better today than they used to be, but still not great. AV gear makers do a lot better job with their power supplies.
    I haven't had a single piece of gear damaged by any power issues, both in my home and my professional gear, going back to 1965. I had one piece of gear damaged when the house we were practicing in took a direct lightning hit. I had left a mic cable, sans mic, plugged into one channel, the connector on the concrete floor of the basement we were in. The hit fried the op amp on that channel, the cost to repair was five bucks.
    Thanks, Bill. Yes, I read your post. I also had a 1970's power amp and 1990's pre-pro destroyed by excess or under voltage. IMHO, a decent line conditioner is never a bad idea on low-current devices. It may not be economically feasible on high-current devices. I've dealt with some pretty crappy power quality here.

  20. #20
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    Default Re: Under voltage protection...how much do I need?

    I think you need to go back and read the AES post. It clearly explains why using protection the wrong way can be worse than no protection at all. If those low-current devices are behind a conditioner, and they're plugged into devices that aren't (conditioned), the path of least resistance just became the signal interfaces between them. Tell me how that's better than having them both subjected to the same power ails, on the power supply -- which should be the most capable and robust circuit in the whole box.

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