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Thread: utility company power

  1. #41
    Join Date
    Jul 2006
    Location
    San Francisco, CA, USA
    Posts
    3,873
    First off, forget the Line to Ground voltage or even the Line to Neutral voltage, all that matters in this case is the Line to Line voltage. If you have some unrelated issue with your Neutral connection or a difference in ground resistance from the neutral bonding point, that will show up in your L-G reading, But the motor is NOT using the neutral point, so the only thing that matters to it is the L-L voltage level.

    People frequently throw around numbers indiscriminately when it comes to voltage ratings and voltage supplies. Officially (for what that's worth), the "Distribution" voltage for residential installations is 120/240V and officially, the "Utilization" voltage, which is what motor mfrs are supposed to design for, is 115/230V, which allows for some normal voltage drop from the source to the motor connections. NEMA MG-1, the design guide for motor manufacturers, also stipulates that motors should suffer no loss of performance or life expectancy as long as the voltage applied to them is +- 10% of the Utilization voltage. So that means a 230V rated motor can accept anything from 253 to 209V without a problem. That said, there are a lot of old motors out there which were designed before these "official" voltage levels were established, and then because of that, there are numerous lazy / ignorant foreign manufacturers who misread (or don't read) our standards and think that 220V is what we have. It's convenient for them because it makes it so they can sell their motors into places where the frequency is different and they don't have to derate them.

    But... because there are also a lot of 208V installations for which the official Utilization voltage would be 200V, a lot of motor mfrs deal with it by making "208/230V" motors and they provide two separate FLC ratings at those two voltages. But there are no separate winding connections for the different voltages. What they do is design the motor for 220V +-15%. That way they are good for 253 - 200V.

    What's important though is EXACTLY what your motor nameplate says. If it says "208/230V" it will be good to 253V line-to-line. If it says "220V 60Hz" on the nameplate very specifically, it is likely an older motor and it will NOT tolerate more than 242V line-to-line. If it says "220V 50/60Hz" it's likely a piece of Chinese junk.
    __________________________________________________ ____________________________
    "Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
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  2. #42
    Quote Originally Posted by Hv&Lv View Post
    If you have 130 (260) call the POCO. That is too high, plain and simple.
    we just finished this house it is on the market for sale tvs lights and all the other stuff that is going to go up in smoke have not been turned on yet

  3. #43
    thank you, read much

  4. #44
    T.M.Haja Sahib Guest
    Quote Originally Posted by Hv&Lv View Post
    Then I believe you have answered your own question...
    No.

  5. #45
    Join Date
    Mar 2008
    Location
    Michigan. It's a beautiful penninsula, I've looked around.
    Posts
    5,916
    Hmm.....

    You guys made me do some homework.

    Surge protectors, arrestors, whatever they are called allow up to 500 volts through before they clamp. Some as low as 300 volts, but none have any true over voltage protection.

    Why is that?

    I am not aware of any over voltage protection for dwellings. Is there such a thing? If yes, where? If no, why not?

    Dropping lines happens here, too. About 3 years ago a 345k was dropped on a 69k and made a fire that burned acres of land. I never heard if there were residential electrical problems Our area wasn't part of the black out.

    So, there is a real risk of having voltages so high they can ruin devices without tripping a surge protector. Or even worse, as previously mentioned, make them smoke.

    I know it's possible to design a crowbar circuit to limit let through voltages to a certain level. I have seen them in power plants. So why couldn't the same technology be used for dwellings?

    Or is it and I just am not aware of the product?
    Cheers and Stay Safe,

    Marky the Sparky

  6. #46
    Join Date
    Oct 2004
    Location
    Antipolo City
    Posts
    469
    Quote Originally Posted by K8MHZ View Post

    I am not aware of any over voltage protection for dwellings. Is there such a thing? If yes, where? If no, why not?

    Dropping lines happens here, too. About 3 years ago a 345k was dropped on a 69k and made a fire that burned acres of land. I never heard if there were residential electrical problems Our area wasn't part of the black out.

    So, there is a real risk of having voltages so high they can ruin devices without tripping a surge protector. Or even worse, as previously mentioned, make them smoke.

    I know it's possible to design a crowbar circuit to limit let through voltages to a certain level. I have seen them in power plants. So why couldn't the same technology be used for dwellings?

    Or is it and I just am not aware of the product?
    I have seen several overvoltage relays that has single phase protection. and I have seen some of these installed to "protect" a 3 phase system. go figure

    many utilities (at least here in my part of the world) have lightning arresters installed in the distribution lines. not to mention the law limiting voltage to below 110% of the nominal.
    NEC 1968 and 1948

  7. #47
    Join Date
    Dec 2006
    Location
    Eastern Oregon
    Posts
    2,762
    Whenever I think I have a voltage issue DIRECTLY causing a problem, I always verify with the 2-3 meters in my truck. Last thing you want to do is get all excited, call in the power co., etc, then come to find out your meter is a little "off".

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