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  • Users: fab1961
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  1. 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...
  2. 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
  3. 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...
  4. 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
  5. 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
  6. 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...
  7. 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...
  8. 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...
  9. 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...
  10. 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...
  11. 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...
  12. fab1961

    VFD with Dahlander winding motors

    Dear all, I have been reading threads 237-345587 and 237-268932, still I feel I need some advice. We have small (4.4/3.3 kW) 2-4 poles motors that originally were meant to run at two fixed speeds. The winding is Dahlander YY/delta. Now we have to add a VFD to get ramps and unlimited number of...
  13. fab1961

    VFD reactors

    Dear all, a question about the values in mH and A of the output reactro between the VFD and the driven async motor. We install them when cables between VFD and motor are longer than 20-25 meters. In case the manufacturer data are not clear or there are delivery or stock problems I believe it is...
  14. fab1961

    three phase contactors damaged

    Dear all, we got from a Customer of ours a picture of a Siemens contactor installed on our machine with a burnt contact. The motor driven is 2.2 kW at 380 V 5.7 A, expected service category is a mix of AC3 and AC4 (Siemens model is 3RT1016-1BB41 which is rated 4 kW in AC3 and 2 kW in AC4). My...
  15. fab1961

    cables and junction boxes in open environment

    Dear all, I work in machine and plant automation engineering. I have been working always with equipment inside buildings. Now I have to connect small async motors and DC sensors outdoor; on top of that the site is really close to the sea and we are considering tropicalized motors etc. Could...
  16. fab1961

    drives and inverters capacitors

    Dear all, I've been told that when a drive or an inverter is kept too long (say more than 2 years) in the store without connecting it to the supply you may need to take care of the internal capacitors - suggesting it may be better to send it back to manufacturer for a sort of reconditioning. Is...
  17. fab1961

    VFD as a power supply frequency converter

    Dear all, we have a machine 70 kW designed for 400 V 50 Hz which has to be installed on a 380 V 60 Hz system. Voltage is ok, it is within the design range, but the mechanics does not allow a change in frequency and we cannot modify the electric panel. So I' ve searched on Internet for frequency...
  18. fab1961

    VFD supply by diesel gen set - low voltage application

    Dear all, I have a similar case to that discussed in thread237-286989 but the generator is definitely oversized in comparison with the inverter (Customer says 200 kVA ?, while our machine is 58 kW total where VFD inside is 18.5 kW) and we are running at low voltage (415 V 50 Hz). Randomly we...
  19. fab1961

    IE2 IE3 efficiency and VFDs

    Dear all, premium efficiency IE3 async motors will be mandatory next year in many countries (U.S. already by 2011, others later). I wonder if driving an IE2 motor with a VFD will be considered acceptable or not. In my opinion the savings in starting and stopping cycles may justify this...
  20. fab1961

    two speed async motors check

    Dear all, I would like to check on site whether an old 2-speed async motor has two separate windings or a Dahlander winding. Chances are for Dahlander, since the speed ratio is 1:2, only horsepower does not fit since it is labeled 3.5/6 kW. If I disconnect cables and measure the resistance...

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