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  1. Join Date
    Jan 2009
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    5,591
    #21
    Quote Originally Posted by vvti2.0 View Post
    Yung cheap avr, ordinary transformer lang laman, yung mamahalin, servo ang laman.
    They both have advantages and disadvantages. Servo AVRs have the advantage of being continuously variable. So if your nominal output is 220V, it is able to maintain that to within a volt, even if the input is all over the place. The only disadvantage is that, the servo is very slow in responding to changes from the input voltage. So say if the outlet voltage changed from 230V to 170V then back to 230V in less than a second (a brown-out), a servo AVR wouldn't be able to keep up the regulation. If a computer is attached to it, it would've undoubtedly restarted.

    A relay-operated AVR on the other hand can switch instantly. However, it can only do boost and cut in increments of between 10-20V. It means that the actual output voltage could potentially range between 200-250V.

    Servo AVRs are ideal if your utility voltage grandually changes theoughout the day. This is typical behavior near industrial areas where heavy electrical machineries exists. The result of such is that, during the day with all the machines running, you may have a nominal 210-220V out of your outlet. But at night, with the equipment turned off, you could see a jump in outlet voltages as high as 260V.

  2. Join Date
    Dec 2009
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    3,006
    #22
    Quote Originally Posted by oj88 View Post
    I can't say that is true. There have probably been more than a dozen 'cheap' AVR's I've seen and opened up. They all work to regulate the output to some extent. I have not seen one that's been hard-wired to be just a pass-thru device.

    But you do get what you pay for. With the multitudes of these cheap brands I've observed, some will only have a single boost and/or buck step. Some just 2 boosts or 2 bucks, not both. Most lack the fuzzy logic to have different boost and buck switchover point so those models would tend to oscillate when the input is near or at the switchover voltage. But for all intents and purposes, they all have a regulating circuit. They're not the best design but if push comes to shove, they do offer a reasonable bit of protection in most cases.

    To test AVRs and UPSes, I use a variac in my lab.
    If you indeed have a lab then you can afford to be definitive

    How come you cant say its true?

    A true AVR will maintain a 220VAC output whether the outlet goes up or down

  3. Join Date
    Feb 2012
    Posts
    1,722
    #23
    Active PFC Power Supply and NON true sine wave UPS. - jonnyGURU Forums3

    I just spoke with both Silverstone and APC. Silverstone is going to get back to me on this question, but APC was pretty clear -- they strongly felt that PFC power supplies should use true sine wave UPSs. They told me that the reason for this was because PFC power supplies require a much faster changeover time when the battery kicks in, and that due to the design of stepped sine wave UPSs, they were not always fast enough to satisfy the power supply. This could lead to the PSU shutting down when the battery tried to kick in. The guy I spoke with said that the stepped sine wave wouldn't "damage" the PSU, but that it simply might not work, and that if it DID work, it might not "always" work. Apparently it depends on the specific power supply.
    Oops! Lesson learned about UPS and active PFC power supplies

    Your computer uses a power supply that utilizes Active Power Factor Correction (Active PFC) to improve efficiency. Power supplies with active PFC may experience incompatibility problems with a UPS that does not provide pure sine wave power output when the power supply switches from AC power to UPS battery power. As a result, when a computer system using a power supply with active PFC is attached to a non-sine wave UPS, the system may shut down when it switches to battery power. Also, if the power supply continues to operate, it may produce a humming or high pitch noise while running on battery. This humming indicates the power supply is operating beyond specified tolerances and may damage the power supply

  4. Join Date
    Oct 2013
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    1,181
    #24
    Quote Originally Posted by kisshmet View Post
    If you indeed have a lab then you can afford to be definitive

    How come you cant say its true?

    A true AVR will maintain a 220VAC output whether the outlet goes up or down
    It will can only maintain 220 kung pataas input before the fuse blows. Kung pababa yan, may certain range lang rin na kaya nya yan i hold at 220 for the servo types.

  5. Join Date
    Jan 2009
    Posts
    5,591
    #25
    Quote Originally Posted by kisshmet View Post
    If you indeed have a lab then you can afford to be definitive

    How come you cant say its true?

    A true AVR will maintain a 220VAC output whether the outlet goes up or down
    It's a difference between having some regulation to not having one at all. And at around P300, I wouldn't call those cheap AVRs a sham... This is the point I disagree with you.

    It's a budget AVR, no more.

    As I've said, even cheap AVRs do afford some regulation. It may not be the best nor does it go anywhere near your definition of a true AVR, but it does the job up to a certain extent without spending a few thousand pesos.

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