How We Test Power Supply Units

By Aris Mpitziopoulos
published

Our methodology, testing equipment, and benchmarks.

Inrush current, or switch-on surge, refers to the maximum, instantaneous input current drawn by an electrical device when it is first turned on. Because of the charging current of the APFC capacitor(s), PSUs produce significant inrush current as soon as they are turned on. A large enough inrush current can cause the tripping of circuit breakers and fuses, and may also damage switches, relays, and bridge rectifiers. As a result, the lower the inrush current of a PSU right as it is turned on, the better.

We also noticed that the lower the input voltage, the lower the inrush current. Thus, when operating with 115 VAC, a PSU has a much smaller inrush current compared with 230 VAC input. Both our Chroma AC source and the Yokogawa power analyzer have the ability to measure inrush current.

(Image credit: Tom's Hardware)

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Aris Mpitziopoulos
Aris Mpitziopoulos
Contributing Editor

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.

30 Comments Comment from the forums
  • JPNpower
    Nobody can fault you guys for not being thorough enough! All we can wish for is that you do these tests a bit more often. I'm at a loss how to navigate the PSU field, and a "Best Picks" section for PSU's would be tremendously helpful.
    Reply
  • Nuckles_56
    Really good article, it is now nice and clear how you guys go and test the power supplies, and as JPNpower said, no one can fault you guys for not being thorough enough.
    Reply
  • ykki
    @JPNpower= I also think a best psu for the money article would be nice but the power supplies in the market pretty much stay the same. We may go for months before seeing any change in the list.
    Reply
  • Kewlx25
    Interesting!
    Reply
  • damric
    Looks legit, Aris.

    THW used to be the laughing stock of PSU reviews, but your recent reviews have changed all of that.

    Keep up the good work!
    Reply
  • damric
    Nobody can fault you guys for not being thorough enough! All we can wish for is that you do these tests a bit more often. I'm at a loss how to navigate the PSU field, and a "Best Picks" section for PSU's would be tremendously helpful.
    @JPNpower= I also think a best psu for the money article would be nice but the power supplies in the market pretty much stay the same. We may go for months before seeing any change in the list.

    I'll make one and submit it through bb-71 to get stickied.
    Reply
  • ykki
    15570872 said:
    I'll make one and submit it through bb-71 to get stickied.

    OK. If someone makes a psu list I'd rather see it from you (or the mods). Good luck.
    Reply
  • damric
    15570891 said:
    15570872 said:
    I'll make one and submit it through bb-71 to get stickied.

    OK. If someone makes a psu list I'd rather see it from you (or the mods). Good luck.

    It will be a group effort for sure :)
    Reply
  • iam2thecrowe
    It would be nice if all manufacturers could do this testing and publish results when they build the things, or even better for it to be a requirement. Then at least there would be less junk PSU's on the market.
    Reply
  • ykki
    15571045 said:
    It would be nice if all manufacturers could do this testing and publish results when they build the things, or even better for it to be a requirement. Then at least there would be less junk PSU's on the market.
    Or more fake reviews.

    Reply