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  1. fab1961

    VFD driving a two-phase motor

    I have to apologize actually the motor is single phase... I am an electronic engineer and sometimes don't use proper terms. Once again this forum has been very useful to me and let me say thank you to everybody.
  2. fab1961

    VFD driving a two-phase motor

    Dear all, I need to run a small (less than 1 kW) two-phase motor (which in turn drives a cooling pump) for a shop test. Motor and pump are designed for a 60 Hz supply, while in our factory we have 50 Hz. My idea is to drive the motor with a VFD whose output frequency is programmed 60 Hz. Point...
  3. fab1961

    three phase voltage in Washington state

    Thank you to everybody for the good advice
  4. fab1961

    three phase voltage in Washington state

    Dear all, we are engineering a machine for a (potential) Customer in Washington state (Pierce county). We are supposing that the power supply is 480V Y 4-wire. Is there a way to doublecheck ? Thank you
  5. fab1961

    VFD size - motor size

    Sorry gentlemen I was in a hurry and forgot to type that we double VDF size when the correct size is not available, normally we use same size as the motor. Or we pickup the next size available. As you pointed out there is current enough.
  6. fab1961

    VFD size - motor size

    Thank you, actually we are using simple V/f on this application.
  7. fab1961

    VFD size - motor size

    Dear all, as a rule of thumb we have always kept the VFD size (in kW) two times the motor size. Now we have a project where a 0.37 kW three-phase motor is to be driven by a 1.5 kW VFD - this is because of delivery times, we can't have a 0.55 kW in time for the job. Any suggestions? Do we have...
  8. fab1961

    power ratio VFD-motor

    Thank you. What worried me most is some potential issues during working, when motors run.
  9. fab1961

    power ratio VFD-motor

    Dear all, given a VFD sized for 4 kW motors is there any problem driving two motors 0.75 kW in parallel? In other words, how much smaller can be the load compared to the VFD? The driving mode is a simple V/f. Thank you
  10. fab1961

    VFD braking with DC current

    Good morning everybody, I would like to understand better (from the theorical point of view) what is the physics of braking with DC. Can you suggest me something to read? Thank you
  11. fab1961

    sharing DC bus between VFDs

    LionelHutz, Waross, thank you for advice. What I was thinking of is using "normal" VFDs and wiring the DC bus using the available terminal blocks. I can confirm that a failure on one drive burns the other ones connected, it happened to us a couple of times using servodrives. In our applications...
  12. fab1961

    sharing DC bus between VFDs

    Dear all, while with drives applications with permanent magnet motors it is a common practice to share the DCbus between drives, I've never come across a similar connection with VFDs (I refer to manuals, case histories etc. - we have been using in time Japanese and European VFDs of different...
  13. fab1961

    braking torque with VFD

    Consider running the motor instead of braking it. When above base frequency (50 Hz Europe 60 Hz USA) the torque is reduced, we enter the constant-power area. If torque were not reduced, then, since power = torquexspeed, we would have infinite power since both speed and torque increase. Also you...
  14. fab1961

    braking torque with VFD

    Dear all, in our applications we use braking resistors connected to VFDs. For a new plant I have to check more precisely how much braking torque is available. I consider the braking torque as [ ( V DCbus / resistor ) / rated motor current ] * motor torque at rated current * K where K is the...
  15. fab1961

    Canadian wye-delta starting low voltage motors

    Thank you everybody for advice - I owe you some more details: I wrote MCC to cut a long story short,in fact we are an European company and it happens to us to make electric panels not only for our machines but also for machines we purchase to deliver turn-key solutions - in this case the load...
  16. fab1961

    Canadian wye-delta starting low voltage motors

    Dear all, to start wye-delta an async motor on a 600 volt grid the nameplate should be 575/1000. I've spent some time over Internet looking for Canadian motor manufacturers but the catalogs I've found say only 575. How do they start their motors there? Reason I ask is that our subcontractor is...
  17. fab1961

    VFD gives insight to process and machines

    Dear all, for once this is not a question. Since this forum has been and currently is very helpful to me, I would like to share an interesting experience I had. We have been using an hydraulic pump async motor driven directly from the line. Recently we added a VFD (for various purposes) and...
  18. fab1961

    VFD I2t

    Sorry, the bitmap attached is only an example. The motor current is 28 A.
  19. fab1961

    VFD I2t

    Dear all, I would like to know what happens in standard VFDs when motor current drawn exceeds the 160-200% of the motor plate. In my application I am changing from a DOL start to A VFD. Motor is a standard 4 pole async 15 kW 400 V. My concern are the unwanted trips. In fact a standard overload...
  20. fab1961

    fuse time-current curves

    Dear all, I am wondering how can I estimate the change when operating fuses under their nominal load - all the standard curves show times for cold fuses - I mean for instance for bimetallic protection devices such thermal overload relays manufacturers show two set of curves, one for cold...

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