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  • #16
    Originally posted by lakeside53 View Post
    A new (they are almost never for sale "used") 10hp unit will set you back a bit under $3k. Cheap for a precision 30 amp three phase supply - and it's "real" 3 phase, better than utility in many cases.
    I checked with Phase Perfect. I was quoted $3195 for a 10 hp unit. Are there other re-sellers that might be cheaper.
    Hi, my name is Wilson and I am a tooloholic.

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    • #17
      Looks like that's the going price right now. Last year American Rotary was selling them for $2895.

      Lot of money but if you have it to spare... you won't regret spending it.

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      • #18
        A big plus on the Phase Perfect. Using one for four years. Great customer service, also.
        Toolznthings

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        • #19
          From what I've been able to find, the PhasePerfect seems to be an electronic PWM drive like a VFD except specifically designed for single phase input and having power factor correction. It may be well worth the money, but you can get a new 10 HP VFD for about 1/4 the cost:


          You may also be able to put together a 240 VDC battery bank from 20 100 Ah batteries at $70 each, so for about $2000 you will have 24 kWh of uninterruptible shop power.
          http://pauleschoen.com/pix/PM08_P76_P54.png
          Paul , P S Technology, Inc. and MrTibbs
          USA Maryland 21030

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          • #20
            However... a 10hp vfd is not a Phase Perfect. The PP puts out a single channel of precision sine wave continuously phase referenced to the pass-though L1/l2 of the single phase input, and in the process creates 3 phase delta. It doesn't care what you connect to it. A VFD "expects" that it is connected to a motor. Although they share similarities, they are quite different in operation.


            Maybe I missed them, but...I find it interesting that after many years there aren't other brands of "phase perfects" to buy...
            Last edited by lakeside53; 11-18-2013, 11:26 PM.

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            • #21
              Originally posted by lakeside53 View Post
              However... a 10hp vfd is not a Phase Perfect.
              Truth........

              A P-P rated for 30A continuous output will be able to supply something much more like 200A or 250A as a motor start surge, without any limiting or tripping off.. A VFD with a similar rating MAY be able to supply as much as 60A for a very short time.

              That high current capability takes much heavier duty devices than the VFD and a good heavy duty power supply as well. Plus the control circuits to do it without a hiccup. That ain't cheap, and the P-P pricing reflects that.
              CNC machines only go through the motions.

              Ideas expressed may be mine, or from anyone else in the universe.
              Not responsible for clerical errors. Or those made by lay people either.
              Number formats and units may be chosen at random depending on what day it is.
              I reserve the right to use a number system with any integer base without prior notice.
              Generalizations are understood to be "often" true, but not true in every case.

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              • #22
                The very high starting current is mostly due to the full voltage starting which was the norm before VFDs became commonplace and inexpensive. Most 3 phase motors have locked rotor and breakdown torque of 2-4x nominal, and current is generally proportional to torque. A VFD uses reduced voltage starting while maintaining maximum torque and thus the current drawn from the single phase mains will be much lower than the current supplied to the motor. If the PhasePerfect must accommodate full voltage starting, it needs to be oversized by 2x to 4x, so you are paying for a 20-40 HP VFD when all you really need is 10 HP. I think it would be worthwhile to try a dedicated VFD for the press, and perhaps smaller ones for the other tools. The total cost would be less than the PhasePerfect, and provides better control of motor startup, speed, and torque, with better efficiency and safety.
                http://pauleschoen.com/pix/PM08_P76_P54.png
                Paul , P S Technology, Inc. and MrTibbs
                USA Maryland 21030

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                • #23
                  But a Phase perfect supplies the entire shop with real three phase; not just one machine. And you don't have to worry about the machine control systems. The OP can ditch the RPC... that's what the PP replaces. Yes, it's oversized, but only for surge; it's continuous rating is still only 30-36 amps. That has a cost but considering what it does it's not unreasonable.

                  As much some think every HSM wants the cheapest solution no matter, not all think this way. Sure, vfds per machine is one solution, but they are not for everyone. Some of us like to rewire the machines, program and fine tune vfds, some just want a power switch. For many the vfd programming is a huge challenge and all they really want to do is make chips. The only thing you have to do with PP is turn it on.

                  I of course have both PP and VFDs
                  Last edited by lakeside53; 11-19-2013, 02:43 AM.

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                  • #24
                    These are the points as I understand them to this point. Please correct me if I am wrong.

                    A 10hp Phase Perfect
                    ---Uses single phase to create 3 phase of the same voltage.
                    --Will replace the rpc that I now have and will be able to run the 7.5hp press without tripping a breaker.
                    --Will allow all my machines to be attached to the same circuit (as they are now)

                    A 10hp VFD
                    --Will need to be dedicated to the press and require that I have other phase conversion for the other machines.
                    --Will convert single phase to 3 phase albeit not as cleanly
                    --Allow for a softer start of the press to reduce required amperage draw.
                    --Is significantly cheaper than the Phase Perfect.

                    I currently have a 50amp service to the RPC. If I use a Phase Perfect, I may need to upgrade wiring to a 60amp circuit. If I add a VFD for the press, I will need to add a circuit or at least add double lug with the rpc circuit. How much current should the vfd be supplied with?

                    The cost of the Phase Perfect is doable, but is it worth 4 times the price of a VFD? The real question is whether I will use the press enough to justify the price of either the PP or VFD. I bought it several years ago from CL, had it at a friends shop (wired up and working) then brought it to my shop when I got it built. I have never actually used the press. It is rated at 100 tons. I would like to get it usable but it is hard to justify the price.
                    Last edited by WilsonT; 11-19-2013, 02:42 AM.
                    Hi, my name is Wilson and I am a tooloholic.

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                    • #25
                      I would not consider the problem PP or VFD for just your press. Only consider it to replace your RPC with a more capable device, and the press problem goes away.

                      To run the press without going the vfd route you'd need a larger RPC anyhow - 15-20hp. That will require an update of your breaker and maybe wiring anyhow. The combined current drawn with large idler and smaller motor is complex (no pun intended) as the idler power factor will be lousy when the smaller motor is running at full load; power consumption isn't vastly increased, but breaker doesn't see power- only current. If power is important to you, a 10-15hp large idler will draw 750-1200 watts at "idle" - a PP is about 100 watts.

                      Adding a vfd to your press may not be as simple as you think - I assume it has control/safety logic that needs to be accommodated. Sure you can work around it, but do you want to?

                      Current for single phase 7.5hp vfd? - 53.9 amps at 230v for the rated output... 71 amps for the 10hp version. No free lunch - that's only a small amount more than the PP will also draw at that output. http://www.polyspede.com/pdf/spedestarb.pdf

                      The PP gives you a lot of flexibility for the future - I don't worry about how to deal with three phase issues on machines I buy now - so long as it's less than 10hp. I plug it in and it works. And.. I can add three phase vfds to machines if I desire (which is why I added a 480v transformer to use the stuff nobody wants!).
                      Last edited by lakeside53; 11-19-2013, 03:14 AM.

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                      • #26
                        I was surprised at the 53.9 amps for the 7.5 HP on 230 VAC, as 5.6 kVA should draw only 24.3 amps. But if there is no power factor correction, then that seems about right, because of the large capacitive load. However, I searched for phase converter drives with PFC and I found this interesting device that not only incorporates PFC but also can boost the 240 VAC input so that the drive can directly supply 480 VAC three phase. The 10 HP version needs a supply rated at 58 amps, and has a PF of 0.98:


                        Interestingly, the email address is phaseperfect.com!

                        The other hits I got were for foreign sources or much smaller VFDs.

                        I wonder if the power factor for the rotary phase converter is lagging (inductive), in which case it may provide PFC for the capacitive load of a standard three phase VFD? But you need to be careful when you combine inductance and capacitance, as resonance can create huge voltages. I built a static phase converter using a 100 mH 10 A reactor and something like 70 uF capacitors, plus some large power resistors (heaters), transformers, and Powerstats. At one point I did not have the resistors connected properly and the voltage meters spiked and there was some arcing until the line breaker tripped.

                        I'm approaching this from an electronic engineering perspective and not so much from that of a machinist who just wants a reliable system to run his machines, so my suggestions might be somewhat "outside the box" and inappropriate for the purpose at hand. But if I wanted to provide three phase power to my shop, I would definitely try to use a standard VFD and provide PFC, or add the battery bank which would also provide the function of a UPS and emergency power.
                        http://pauleschoen.com/pix/PM08_P76_P54.png
                        Paul , P S Technology, Inc. and MrTibbs
                        USA Maryland 21030

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                        • #27
                          I have read this thread and am interested that no replies mentioned a three phase generator.
                          The RPC approach seems like an electricity waste to me and the VFD means the shop is still totally dependent on an increasingly unreliable and expensive grid.
                          The genset would supply all of the required power and possibly a little more , give him immunity from blackouts etc .

                          Just my approach.
                          Michael

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                          • #28
                            Michael,
                            You may have missed the almost incidental mention of the three phase generator by PStechPaul in his first response. He said that I might use the generator along with a VFD to power the shop. Although, I am not sure that the generator would be more reliable and less expensive than the grid. We do occasionally have blackouts (usually during the worst weather), but for the most part the grid is pretty reliable. As far as expense is concerned, the units that I have seen that will generate three phase and large enough to power the shop are diesel. While I realize that diesel engines will run for a long time with proper maintenance, they run best if run frequently. Also, diesel seems to be the most expensive fuel currently available. (Although, I have looked into Bio-diesel, and if diesel goes back to where it was a couple of years ago, I might start making some.) Who knows, maybe using the genset with a battery bank would provide the a good, even three phase without the grid.
                            Hi, my name is Wilson and I am a tooloholic.

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                            • #29
                              Originally posted by PStechPaul View Post
                              The very high starting current is mostly due to the full voltage starting which was the norm before VFDs became commonplace and inexpensive. Most 3 phase motors have locked rotor and breakdown torque of 2-4x nominal, and current is generally proportional to torque. A VFD uses reduced voltage starting while maintaining maximum torque and thus the current drawn from the single phase mains will be much lower than the current supplied to the motor. If the PhasePerfect must accommodate full voltage starting, it needs to be oversized by 2x to 4x, so you are paying for a 20-40 HP VFD when all you really need is 10 HP. I think it would be worthwhile to try a dedicated VFD for the press, and perhaps smaller ones for the other tools. The total cost would be less than the PhasePerfect, and provides better control of motor startup, speed, and torque, with better efficiency and safety.
                              AS mentioned, of course the P-P supplies a single (3rd) phase of 230VAC to complete the 3 phase, which is the same job the RPC does. A VFD supplies THREE phase outputs, so for equal current capability the VFD must have THREE TIMES the amount of expensive output devices, rectifiers, heatsinks, and filter capability.

                              Then also, the VFD in this size will likely need to be derated due to using single phase input. So even if a 10HP was OK, it might have to be rated at 20HP just to get the 10HP capability on single phase input.

                              You CAN use a VFD set to 60Hz (50 Hz for others) to act a bit like a phase perfect. But you need it to be rated at the starting surge of your largest motor, plus the FLA of everything else, AFTER derating for single phase input.

                              Then also, either an RPC or the P-P has an ADVANTAGE vs a VFD, in that both the RPC and P-P can return energy to the power line, where the typical VFD cannot. (we are not discussing "system drives" here.) The P-P is fully bidirectional, where an RPC is about 3/4 to 7/8 effective on bidirectional power flow, due to impedance on the generated leg. Returned energy is from an overhauling load, or certain kinds of braking setups.
                              CNC machines only go through the motions.

                              Ideas expressed may be mine, or from anyone else in the universe.
                              Not responsible for clerical errors. Or those made by lay people either.
                              Number formats and units may be chosen at random depending on what day it is.
                              I reserve the right to use a number system with any integer base without prior notice.
                              Generalizations are understood to be "often" true, but not true in every case.

                              Comment


                              • #30
                                I have a silly question. Why is the hydraulic press starting with a load on it? I believe it should just be spinning bypassing oil until the valve to the cylinder opens, then basicly free running until the ram contacts the load. Just a thought.
                                From the State of Lemmings, where three counties out of twenty-seven call the shots.

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