Announcement

Collapse
No announcement yet.

Kearney & Trecker Milwaukee Model K No 3 follow me home.(pics)

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #31
    Originally posted by outlawspeeder View Post

    Bolting it down I'll skip that but may put mortar around the base. (easy to clean, & stops mice)
    your mice know how to use a mill? I'd personally use a keyed switch to stop them, but that's just me

    Comment


    • #32
      'Tis true. You must derate a VFD designed for three phase input. Something like 1.75 is the real number, but 2x is what will be the closest to real size available. Some of the cheaper ones designed for hobbyists are pre-derated, but those are mostly smaller units. I had a great PDF explaining in detail why this is, but I have lost it, so I'd recommend a google search "derating vfds for single phase input" for further reading.
      21" Royersford Excelsior CamelBack Drillpress Restoration
      1943 Sidney 16x54 Lathe Restoration

      Comment


      • #33
        The real reason you need twice the size is only partly that 2 phases are supplying all the power, that part was easy to solve. The bigger problem is that rectified DC from 3 phase has a relatively small amount of ripple because the phases overlap. Not so for single phase where the ripple is huge on to off swings that have to be filtered by much larger capacitors. You get them by using a much larger VFD.

        Comment


        • #34
          2 wires is 1 phase.
          2 phase needs 4 (or 3) wires.

          -Doozer
          DZER

          Comment


          • #35
            There's a mill that'll do some work. I'm surprised a 10hp 50 Cat machine is 2000-3000, I'd have thought it heavier......my Elliot, 40 taper, is Net wet 3130lbs and seems like its got endlesss torque, you'd think massive 50 taper 10hp would be double the weight. Anyway, good on you, have fun with it, and keep away from the moving arbor
            in Toronto Ontario - where are you?

            Comment


            • #36
              Originally posted by Mcgyver View Post
              There's a mill that'll do some work. I'm surprised a 10hp 50 Cat machine is 2000-3000, I'd have thought it heavier......my Elliot, 40 taper, is Net wet 3130lbs and seems like its got endlesss torque, you'd think massive 50 taper 10hp would be double the weight. Anyway, good on you, have fun with it, and keep away from the moving arbor
              It weighs about 7800 lbs. I was a bit confused at first, too, but Outlawspeedracer was saying the mill was 2000-3000 lbs. heavier than he expected because it was a No. 3 instead of the No. 2 it was listed as.

              Originally posted by Doozer
              2 wires is 1 phase.
              2 phase needs 4 (or 3) wires.

              -Doozer
              Garyhlucas is spot on with his description. 2 hot legs are best described as "split phase" and you're right that it is derived from just one phase of the three phases provided by the power company. But when you start talking about the actual electronics involved, that single phase or "split phase" service provides two hot legs, each 180 degrees apart. Those two legs could be called "phases" but separated by a different phase angle than what we're used to in normal 3-phase service. I've designed DC power supplies for both single phase and three-phase inputs (I didn't even think of this with regard to a VFD, probably because I never really thought about how a VFD works) and Garyhlucas is right: with 120* phase separation, the ripple current is less and the capacitors therefore tend to last longer, run cooler and/or can be smaller. In the case of the VFD, not only do you have a higher input current, but you are now separated by 180* so you have two effects increasing the ripple current.

              Comment


              • #37
                Click image for larger version

Name:	single.jpg
Views:	165
Size:	16.4 KB
ID:	1850346
                Click image for larger version

Name:	split.jpg
Views:	160
Size:	21.5 KB
ID:	1850347
                Click image for larger version

Name:	three.jpg
Views:	164
Size:	25.2 KB
ID:	1850348

                I don't want to steal the thread, but I'm just saying: Split phase sure does look like more phases than one to me. Click image for larger version

Name:	whistle.gif
Views:	164
Size:	1.2 KB
ID:	1850349
                21" Royersford Excelsior CamelBack Drillpress Restoration
                1943 Sidney 16x54 Lathe Restoration

                Comment


                • #38
                  It weighs about 7800 lbs. I was a bit confused at first, too, but Outlawspeedracer was saying the mill was 2000-3000 lbs. heavier than he expected
                  right. thanks....should have read more carefully.
                  in Toronto Ontario - where are you?

                  Comment


                  • #39
                    Originally posted by Fasttrack View Post
                    ...Garyhlucas is spot on with his description. 2 hot legs are best described as "split phase" and you're right that it is derived from just one phase of the three phases provided by the power company...

                    Gary said, "...2 phases are supplying all the power"....

                    2 legs (wires) might be supplying the power, but that is 1 phase.
                    2 legs (wires) might be supplying the power, but that is 1 phase.
                    2 legs (wires) might be supplying the power, but that is 1 phase.

                    Gary said nothing about split phase. Center tapped, want to call it something else,
                    sure, fine, go ahead... But it is not 2 phase. Stop calling legs, phases. You confuse the newcomers.

                    -Doozer


                    DZER

                    Comment


                    • #40
                      Originally posted by The Metal Butcher View Post

                      I don't want to steal the thread, but I'm just saying: Split phase sure does look like more phases than one to me.
                      It has ZERO rotational value. Try to start a 2 phase motor with it. Not going to do anything but hummmmm.

                      90° 2 phase will start a motor. Center tapping a transformer is not and has never been 2 phase.
                      You can offset tap a transformer (call it autotransformer if it makes you feel warm and fuzzy)
                      and get a phase shift, but not center tapping.

                      -Doozer
                      Last edited by Doozer; 01-21-2020, 04:36 PM.
                      DZER

                      Comment


                      • #41
                        Originally posted by Doozer View Post


                        Gary said, "...2 phases are supplying all the power"....

                        2 legs (wires) might be supplying the power, but that is 1 phase.
                        2 legs (wires) might be supplying the power, but that is 1 phase.
                        2 legs (wires) might be supplying the power, but that is 1 phase.

                        Gary said nothing about split phase. Center tapped, want to call it something else,
                        sure, fine, go ahead... But it is not 2 phase. Stop calling legs, phases. You confuse the newcomers.

                        -Doozer

                        I hear you. But you're not hearing me. From an electrical engineering or physics perspective, split-phase contains two distinct phases. In fact, in signal processing, we talk about multiple phases that have nothing to do with power generation and we talk about phase margin with regard loop stability. We also talk about phases in the contexts of lasers and photonics. "Phase" is a general term that has developed a very specific meaning to electricians, machinists, millwrights, farmers, and generally people like us who interact with electric motors in more than a "theoretical" way. But that is not the only meaning of the word.

                        I guess my point is that, when communicating with people from different backgrounds (which is what is so great about this forum), semantics can be challenging. I'm just giving Gary the benefit of the doubt and have chosen to understand "2 phases" in the context of a physics or EE perspective, not the practical perspective where 2 phase and split phase are (as you point out) very different.

                        Comment


                        • #42
                          Well instead of saying run-out, let's say whompey-jawed then.

                          -D
                          DZER

                          Comment


                          • #43
                            I had this discussion years ago with a friend who was a journeyman electrician and instrumentation tech. He kept referring to the 240 volts (center tapped, as is usual in the US) as "two phase" 120 volt.

                            I pointed up at the top of the pole in front of my neighbor's house at the 4.6KV three phase and said "OK, that's three phase, right? A-B, B-C and C-A, right?"
                            "Right".
                            "And you see the two leads from the three phase down to the transformer on the pole - let's say that's the A-B phase. Single phase, right?"
                            "Right."
                            "And on my side of the transformer you say it's two phase? Where did that second phase come from?"
                            "Ummmm....."

                            But he still insisted it was two phase. Oh, well.

                            -js
                            There are no stupid questions. But there are lots of stupid answers. This is the internet.

                            Location: SF Bay Area

                            Comment


                            • #44
                              When I hook my scope up to 120 volts in the shop I get a single sine wave that looks just like the sketch in post #37.

                              When I hook it up to 240 volts I get *a single sine wave* with twice the peak voltage. Sure looks like single phase.

                              -js
                              There are no stupid questions. But there are lots of stupid answers. This is the internet.

                              Location: SF Bay Area

                              Comment


                              • #45
                                Gentlemen, the last operating 2 phase power system in the US was on the back end of Philly Navy Yard in the 70s. It has been discontinued and rebuilt as 3Ø.

                                2 Phase has continued on as a nomenclature in some geographical areas, when describing Open Delta transformer configurations where 2 phases at Primary (7200v) and Neutral are brought to the transformers and 3Ø "wildcat" low voltage departs the bank. The nomenclature is commonly used by Central Maine Power and companies in Nebraska and the Dakotas.

                                Great enjoyment can be had on storm recovery operations such as RG&E territory watching linemen argue over 2 phase and Wildcat 3Ø banks. Maximal entertainment is reached when the crews from Quebec enter the discussion to set the record straight.

                                Comment

                                Working...
                                X