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A large Single Phase motor, which is better 230 or 115 volts?

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  • #31
    This is why there are guidelines and warnings about the minimum size of extension cords for electrical equipment such as string trimmers, mowers, chain saws, and circular saws, which typically are used at some distance from a power source. Most extension cords are 16 gauge, and a 100 foot cord will have almost 1 ohm of resistance. So a 2 HP saw will draw about 12.5 amps at 120 VAC, which means the motor will see about 107.5 volts. This would result in only about 1.8 HP. If you attempt to get the full 2 HP, the current would increase to about 14.2 amps and the voltage on the motor will be 105.8 VAC.A 14 gauge cord will have only about 1/2 ohm resistance which will result in more power and less chance of overload.
    http://pauleschoen.com/pix/PM08_P76_P54.png
    Paul , P S Technology, Inc. and MrTibbs
    USA Maryland 21030

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    • #32
      Originally posted by Bruno Mueller View Post
      I'm a little confused.
      The discussion is about connecting motors in the USA, is that correct?

      Now I read here about 220/240V. Is both common there?

      Here in mainland Europe we have the voltage 220/240V DC 1phase and 360/400V DC 3phase.
      Our standard is 220/240V DC 1 phase, up to a motor power of about 2,5KW consumption. Motor power above that is always 3 phase with 360/400V.
      Industry standard is always 3-phase with 360/400V, even with smaller motors.

      Every household has a connection with 3 phases and max.400V DC at the power supply system.

      I always thought in the USA there is only 110/120V.

      I am not an electrician
      120v in the USA is really split phase with a neutral. Every house has two legs going into it making 240v.
      So you can run two separate legs in the house, each 120v with a neutral which is like a center tap on a transformer. If there's 2 outlets in a room, each ones hot leg is seperate, IE, the hot legs going to the house, you can actually get 240v out combining the hot legs, discarding the neutrals. That's the last resort to get 240v in a room that otherwise doesn't have 240v.
      Theres other variations in the USA that depart slightly in voltage, like 208v, but I have no experience with it. I'm not an electrician, so don't listen to me. Absolute worst thing is to burn down your house.

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      • #33
        The reason for the 208 3 phase power is that it is fairly close to 230/240V, so motors etc will work on the 208V, and the voltage from the lines to neutral is 120V.

        So, the system can provide 3 phase and single phase in much the same way as your 220V/380V system does.

        The power company will not provide 3 phase to a single house, but the 208 3 phase is typically provided to apartment buildings. It gives 3 different circuits of 120V, and also provides 3 phases of a voltage (208V) that will run 240V appliances fairly well, plus it efficiently balances the load on the 3 phase incoming power.

        Whenever a large load is considered, 3 phase power is always the best type. However, for houses, air conditioning electric cookers, and electric heat (if used), will run from the 240V circuit in single phase, even though it might be better to run with 3 phase, so no three phase to houses.
        3751 6193 2700 3517

        Keep eye on ball.
        Hashim Khan

        If you look closely at a digital signal, you find out it is really analog......

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        • #34
          Originally posted by J Tiers View Post
          The reason for the 208 3 phase power is that it is fairly close to 230/240V, so motors etc will work on the 208V, and the voltage from the lines to neutral is 120V.

          So, the system can provide 3 phase and single phase in much the same way as your 220V/380V system does.

          The power company will not provide 3 phase to a single house, but the 208 3 phase is typically provided to apartment buildings. It gives 3 different circuits of 120V, and also provides 3 phases of a voltage (208V) that will run 240V appliances fairly well, plus it efficiently balances the load on the 3 phase incoming power.

          Whenever a large load is considered, 3 phase power is always the best type. However, for houses, air conditioning electric cookers, and electric heat (if used), will run from the 240V circuit in single phase, even though it might be better to run with 3 phase, so no three phase to houses.
          Interesting, so is it even a possibility that an apartment in an apartment building could have three seperate 208v legs, and one could splice into three separate outlets and have three phase 208v to run a small CNC machining center in their living room on true 3 phase power?

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          • #35
            Originally posted by J Tiers View Post
            The reason for the 208 3 phase power is that it is fairly close to 230/240V, so motors etc will work on the 208V, and the voltage from the lines to neutral is 120V.

            So, the system can provide 3 phase and single phase in much the same way as your 220V/380V system does.

            The power company will not provide 3 phase to a single house, but the 208 3 phase is typically provided to apartment buildings. It gives 3 different circuits of 120V, and also provides 3 phases of a voltage (208V) that will run 240V appliances fairly well, plus it efficiently balances the load on the 3 phase incoming power.

            Whenever a large load is considered, 3 phase power is always the best type. However, for houses, air conditioning electric cookers, and electric heat (if used), will run from the 240V circuit in single phase, even though it might be better to run with 3 phase, so no three phase to houses.
            When I lived in Rochester NY, RGE, the electric supplier would not provide more that 400A single phase service, if you needed more for any reason, 3 phase was a must. Of course, it would take quite a house to need more than 400A single phase service. Large apartment buildings, as Jerry states, were 3 phase service.

            Here, in Anderson, SC, there IS 3 phase power to houses in some areas. I was very surprised to see that ! Where I seen it was a area of old large homes 4000-6000 sq ft. Anderson's nickname is the "Electric City", it was the first area in the south to have electricity (1895).

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            • #36
              Apartment buildings with a 208/120V service should have stoves and dryers with heating elements designed for 208V, not 240V...they do make them.
              Location: Saskatoon, Saskatchewan, Canada

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              • #37
                I am far from being a qualified electrician, but I have managed to sort out most problems myself
                .I fitted a new to me, secondhand electric motor to one of my lathes, the motor was a 110 220 job.
                Initially I wired it up to run on 110 volts. It ran fine, reversed ok, but obviously laboured starting the lathe in higher speeds.
                After a bit of headscratching I decided to try 220 volts, so bought some new cable of appropriate size and wired in to the nearest 220 line.
                For the rest of the years I ran it the lathe started up swiftly and strongly. Last time I visited it was still running well.
                Using 220 for larger motors when reasonably possible. seems a sensible approach.
                Regards from the snow covered north David Powell

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                • #38
                  Originally posted by RB211 View Post

                  Interesting, so is it even a possibility that an apartment in an apartment building could have three seperate 208v legs, and one could splice into three separate outlets and have three phase 208v to run a small CNC machining center in their living room on true 3 phase power?
                  Doubtful. They would be wired so each got just single phase..... two wires for 208 plus a neutral.

                  Originally posted by Arcane View Post
                  Apartment buildings with a 208/120V service should have stoves and dryers with heating elements designed for 208V, not 240V...they do make them.
                  "Should", and "Do" are two different things, especially when dealing with landlords. But most any built-in or "supplied" appliances would be expected to be for the available voltage. 208 vs 220 is no big deal. 208 vs 240 is more so, but there are motors that will cover that range acceptably.
                  3751 6193 2700 3517

                  Keep eye on ball.
                  Hashim Khan

                  If you look closely at a digital signal, you find out it is really analog......

                  Comment


                  • #39
                    If you have 208 volts and a neutral, there will be 120o phase angle from each to neutral. So you could create a center tap between two phases and the phase angle from that to neutral will be correct for the third phase. But it will be just 60 volts, so you need a 2:1 boost transformer to get the desired 120 VAC to neutral and 208 VAC on all three phases. Similar to a Scott-T configuration, but like this:

                    Click image for larger version

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                    http://pauleschoen.com/pix/PM08_P76_P54.png
                    Paul , P S Technology, Inc. and MrTibbs
                    USA Maryland 21030

                    Comment


                    • #40
                      Originally posted by Bruno Mueller View Post
                      I'm a little confused.
                      The discussion is about connecting motors in the USA, is that correct?

                      Now I read here about 220/240V. Is both common there?

                      Here in mainland Europe we have the voltage 220/240V DC 1phase and 360/400V DC 3phase.
                      Our standard is 220/240V DC 1 phase, up to a motor power of about 2,5KW consumption. Motor power above that is always 3 phase with 360/400V.
                      Industry standard is always 3-phase with 360/400V, even with smaller motors.

                      Every household has a connection with 3 phases and max.400V DC at the power supply system.

                      I always thought in the USA there is only 110/120V.

                      I am not an electrician
                      I am sorry,
                      I confused alternating current (AC) with direct current (DC).
                      Of course we have 3 phase alternating current (AC) in every house. When the three phases are measured against each other, 360/400Volt comes out. But each phase has only 220/240V against the neutral conductor.
                      Click image for larger version

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                      Last edited by Bruno Mueller; 12-02-2020, 06:59 AM.
                      Many greetings from Germany
                      Bruno
                      http://www.mueller-bruno.de

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