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5.5KW Motor and VFD, Have I got this right?

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  • 5.5KW Motor and VFD, Have I got this right?

    I have a Shizuoka CNC mill with a 2.2 HP motor driving the spindle via a CVT assembly plus hi and lo gearing. I want to do away with CVT pulley system and control the mill using a VFD from Mach 3. I don't envisage any problems with the conversion but I could do with some advice on motor selection. I have purchased a 5.5 KW motor, but I am not sure I have made the correct purchase. From the plate shown, can this motor be configured to be powered from a VFD with a 240v input. Thanks for any help.


  • #2
    The motor does not show that 240 volts is an option, so probably not. If you use a three phase step up (from 240) transformer you can do it with a 400v class vfd. Connect as Delta for 400, Y for 690. 5.5kw on Y, 6.6kw on Delta. If you go this route and you are not experienced, consult with someone that really knows what they are doing. There are several no-so-obvious code requirements for transformers (fusing, grounding, clearance etc) , and it's easy to die from 400 or 690.
    Last edited by lakeside53; 12-27-2013, 07:35 PM.

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    • #3
      Thanks Lakeside, that is very helpful.

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      • #4
        Not a good choice
        the motor is probably 150 % larger than the original motor.
        I can see however that you want more torque as you are going to direct drive..that part is OK
        The motor looks, as Lakeside said, to be a single voltage delta motor and of too high a voltage.
        I have hooked up 480 volt 3 phase in home shops, but also recommend that you stay with a lower voltages.
        Too easy to get into big trouble
        Rich
        Green Bay, WI

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        • #5
          There was a discussion on PM in April on this matter, with a similar motor size as to the OP motor and this reference came up, which may be useful, if the OP can take a power hit, as it seems
          the 'new' motor is overrated for the original application. Ref: http://www.inverterdrive.com/HowTo/2...400V-AC-Motor/
          This is a UK website.
          Last edited by sch; 12-27-2013, 07:36 PM.
          Steve

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          • #6
            The new motor isn't overated for a direct drive application. HP at low rpm has to come from somewhere, and the only place it can is from increased torque, so 3X original isn't a huge jump.

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            • #7
              There are some drives that incorporate a boost converter so that a 120 VAC source can drive a 220/240 VAC motor, but I'm not sure if there are any which run 440/480 VAC motors from 220 VAC. Here are the specs:
              http://www.wolfautomation.com/assets...ing_manual.pdf

              It is possible to run a 5 HP 440 VAC 2 pole motor at half voltage and half speed using a 220 VAC source and a VFD. You can get the same torque as the 5 HP motor, but only half the continuous power. And you can run it at full speed using field weakening, but that may not be advisable.

              The nameplate voltage rating on this motor is confusing, showing 400/690 delta/wye for 50 Hz. That seems to be reversed, as the delta voltage is phase-to-phase which is sqrt(3) times the wye phase-to-neutral. In the US the standard is 480 VAC delta and 277 VAC wye. Perhaps this motor can be externally configured for wye or delta.
              http://pauleschoen.com/pix/PM08_P76_P54.png
              Paul , P S Technology, Inc. and MrTibbs
              USA Maryland 21030

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              • #8
                Thanks for all the input guys. In the way I want the mill to work it is clear I have made the wrong purchase. I had hoped that there might have been a kink or workaround that I could have used and it seems there is, but with loss of some functionality. I didn't pay a lot for the motor and I have learn't a lesson along with some good advice. Cheers again and all the best.

                Edit: if anyone is interested in the machine the motor is going on, here is the account of the rebuild I did earlier on this year.

                http://www.alloyavenue.com/vb/showth...ka-CNC-Rebuild
                Last edited by Zadig; 12-28-2013, 07:21 AM.

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                • #9
                  This is a standard configuration for large motors. They operate at higher voltages. This reduces the current through both the motor and the switchgear. Power (Watts) = Voltage X Current (Amps).

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                  • #10
                    from what grid can you get 830 volts?
                    Last edited by dian; 12-28-2013, 12:22 PM.

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                    • #11
                      Originally posted by dian View Post
                      from what grid can you get 830 volts?
                      Good point. The maximum nominal voltage for "low voltage" wiring, switches, and protective devices is 600 volts, and that is fairly rare. 830 VAC happens to be the phase-to-phase voltage of system with 480 VAC L-N, which is also something I have never encountered. This seems to be a metric motor for European power which I believe is 220 VAC phase-neutral or 380 phase-to-phase. Could it be that whoever made that nameplate was dyslexic and swapped the 8 and 3? But that does not explain the 400/690 at 50 Hz. It should be 400/230. I suspect this could be a special motor, or one which was incorrectly built and/or labeled and sold as surplus or "irregular".

                      A search for this company comes up with a website for "Enhanced Capital Allowance", or ECA, which seems to be a designation for energy-saving devices. Maybe someone came up with the idea that a higher voltage motor would draw less current and thus qualify.
                      http://www.plant4theplanet.com/

                      I found a catalog of these "Euromotors" (12MB):
                      http://www.browngroupltd.com/catalog...tor%202007.pdf

                      In the technical information it states that they supply motors for the "new" IEC 38 Standard Voltages of 230, 400, and 690. But the list of motors shows only 400 VAC for three phase and 230 VAC for single phase.

                      Here is a summary of IEC 38 for the 400 VAC standard:
                      http://www.dmc-global-service.com/Ma...EI3604E_ms.pdf

                      Finally I found a reference for 400/690 VAC systems:
                      http://en.wikipedia.org/wiki/IEC_60038

                      But it does not mention a 480/830 system for 60 Hz. It should be 277/480 or 347/600.
                      Last edited by PStechPaul; 12-28-2013, 06:33 PM. Reason: was 480/690
                      http://pauleschoen.com/pix/PM08_P76_P54.png
                      Paul , P S Technology, Inc. and MrTibbs
                      USA Maryland 21030

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                      • #12
                        Paul, you seem to be tying yourself in knots.

                        The nameplate voltage rating on this motor is confusing, showing 400/690 delta/wye for 50 Hz. That seems to be reversed,
                        I suspect this could be a special motor, or one which was incorrectly built and/or labeled and sold as surplus or "irregular".
                        1: Voltages shown on the motor plate are phase-phase, so it's a normal motor with 400v windings:-

                        400v phase-phase on a delta connected motor provides 400v per winding.
                        690v phase-phase on a wye connected motor provides the same 400v per winding.

                        690v is not uncommon in heavy industry, offshore etc.

                        830 VAC happens to be the phase-to-phase voltage of system with 480 VAC L-N
                        Could it be that whoever made that nameplate was dyslexic and swapped the 8 and 3?
                        2: Google 3 phase 830v and you will find plenty of mentions on its uses in the oil industry. You will find a lot of commercial test instrumentation (power analysers etc.) has this as its upper working limit. It was apparently chosen to enable simple re-working of 480v delta motors to wye for use with long cable lengths.

                        But it does not mention a 480/690 system for 60 Hz.
                        3: - ? typo ?


                        Cheers

                        .

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                        • #13
                          The 6,6Kw is the power at 60Hz. In Europe, motors 400/690V are normally star/delta start motors. This allows for a reduced voltage start of high powered motors. The cement factory in our town use 500V motors to reduce the current/cable diameter in the long conveyor systems.
                          At work, we have a 840Kw motor on our metal shredder that has a F.L.A of only 98A @ 6200V 50Hz. This is a star connected, direct start motor that has a dedicated 15Kv/6,2Kv 2000Kva transformer. To "soften" the start, 3 oil dipped resistors of 4,5 ohm connected in series with the motor, reduces the starting "locked rotor" current from 480A to 400A, allowing the motor to start without tripping the main breaker.
                          Helder Ferreira
                          Setubal, Portugal

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                          • #14
                            I stand corrected, and have learned something. However, there is not much reference to 830 VAC, and in the Wiki article it only says it is sometimes used for special installations, such as oil pumping. And in the same search I found an oil pump motor rated at 830 RPM:
                            http://www.temcoindustrialpower.com/...nt/M04397.html

                            I Googled for 3 phase 830v and came up with only a few genuine hits (I don't count Walmart or other sites that offer the "best deals" on gobbledegook or whatever you search for). There are some analyzers which are rated up to 830V and also some motor controllers. I found an IEEE standard which has been withdrawn, indicating that this is a very rare and perhaps obsolete system:
                            http://standards.ieee.org/findstds/s.../464-1981.html

                            I did find information on wye-start delta-run motors which are reconnected for effectively lower voltage starting. This is not really needed when VFDs are used:
                            http://www.usmotors.com/TechDocs/Pro...-DeltaRun.aspx
                            Last edited by PStechPaul; 12-28-2013, 06:37 PM. Reason: wye-delta
                            http://pauleschoen.com/pix/PM08_P76_P54.png
                            Paul , P S Technology, Inc. and MrTibbs
                            USA Maryland 21030

                            Comment


                            • #15
                              Originally posted by dian View Post
                              from what grid can you get 830 volts?
                              Any! Electricity is transmitted from the power station generators (3 phase alternators) at very high voltage, this voltage is reduced at local transformer substations for distribution to consumers. Domestic and light industrial premises usually share the same supply with 3 phases being delivered to industrial premises and 1 phase to domestic premises. Large industrial sites usually have their own substation, any required voltage is available but agreed standards are maintained to permit manufacture of motors and ancilliary equipment by others.
                              Dave

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