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  1. DickDV

    VFD problem....

    Sometimes you can get that kind of motor behavior when the drive is set up as sensorless vector but the motor ID run has not been made or is defective. If the drive can be configured as a V/Hz drive, see if it will run the motor properly in that mode.
  2. DickDV

    Speed fluctuation in VSD driven pump

    Are these motors running independent pumps or are the two pumps piped in parallel? If in parallel, are the VFD's running independently against independent setpoints or are the two VFD's linked together in some way? If linked, please describe how.
  3. DickDV

    Replacing MG set

    The old MG set motors will likely not be suitable for rectified unfiltered DC power without significant derating. The magnetics were designed for smooth generator DC and will overheat on DC with ripple on top.
  4. DickDV

    Single phase 1/2 hp motor Class I Div II Groups B, C, D

    I could easily be wrong on this but I thought there was no electrical equipment allowable in Group B.
  5. DickDV

    How long would you run a VFD after issuing a stop command?

    The stress on power-up is largely a matter of managing the inrush current to the DC bus capacitors. I would think that a properly-designed lightning suppression network ahead of the drive would be a better option that frequent power cycling. Whether the inrush current is limited by precharge...
  6. DickDV

    How long would you run a VFD after issuing a stop command?

    Cycling input power on a VFD is very stressful to its power components and should be avoided whenever possible. Surely, cycling should be limited to not more frequent than once per hour.
  7. DickDV

    ABB Drives Blown Boards.

    Haven't seen this with any of the ACS or ACH units. It would be helpful to be more precise as to which models are having trouble.
  8. DickDV

    VFD High DC Bus Voltage

    A key piece of information is missing here. Is the incoming AC power balanced to ground, floating to ground, or deliberately offset to ground as in 120/208 or 460V corner-grounded delta. Floating or unbalanced input power can cause the output side capacitance to charge up the DC bus. I've...
  9. DickDV

    VFD High DC Bus Voltage

    The capacitance between the phase leads or maybe between the leads and ground are likely different. At such long lead lengths, that can be the difference.
  10. DickDV

    380 volt 60 HZ to 460 volt 60 HZ

    While haven't personnally done this, I believe that the addition of a 90VAC bucking autotransformer in the 480VAC supply lines would do the same thing = 380-400VAC at the motor.
  11. DickDV

    3 motors controlled by a single VFD

    jraef, first, thanks for the CB recommendations on the individual motor leads. I've always recommended a fused disconnect with overload relay but yours sound better and with only one device. I'm curious why the dread about single phasing one of the motors.
  12. DickDV

    VFD beginner question.

    An output short circuit fault with the motor leads disconnected is usually a shorted IGBT. They will generally short when they fail but, in your case, they didn't. Sometimes, at a test voltage of 1.5V, the short will not appear where, at operating voltage of 660VDC, it will. That's probably...
  13. DickDV

    Terminator networks for VFD

    Allen Bradley has promoted their "motor terminal protector" for many years but, while it may protect the motor adequately, it does nothing to quiet the motor leads. As skogs says, a reactor or dv/dt filter mounted as close to the drive output terminals as possible is preferred.
  14. DickDV

    VFD HP change - 60HZ to 50HZ

    jraef is correct. Most drives rated 480V are actually rated 380-500V when you read the fine print. And, no, you don't have to make any hardware changes and generally no software changes either. But note his comments about the output voltage being limited to the input voltage. That pretty...
  15. DickDV

    Power output of a 3x460V motor running on VFD limited at Vout=400V

    Assuming the motor will be in a constant hp range from 50 to 73.3Hz, then the hp throughout that range will be equal to the hp at 50hz. The hp at 50hz will be 50/60 of the nameplate hp at 60hz assuming you program the drive for constant V/hz ratio from 0 to 50hz equal to 480/60=8.00. Then...
  16. DickDV

    motor overheating with VFD, and incorrect amp readings

    It's my mistake on the insulation class ratings. The numbers I had were rise only. Add 40 degrees C ambient to them to get total temp and they math ScottyUK's. I would say the motor is not overheating based on the numbers measured at the outside frame surface.
  17. DickDV

    motor overheating with VFD, and incorrect amp readings

    The information on insulation class temps that I had came from MG1 Part1 where Class B is 85 degrees C, F is 110 C, and H is 135 C. Now I'm curious about the differences between IEC 60085 and NEMA. Can anyone explain the differences? Because, as ScottkyUK points out, that's a significantly...
  18. DickDV

    motor overheating with VFD, and incorrect amp readings

    First, it is a waste of time to measure anything on the motor leads. Even true rms meters will not read accurately. In addition, it is very likely that the voltages far exceed CAT III levels so you and your meter are at risk. Believe the drive display. Second, while reactors are nice cheap...
  19. DickDV

    Enlightenment in a dynamical brake scheme

    I would caution you on increasing the brake intensity. The braking action is done by passing DC thru the motor while it spins. There is a limit to how much DC current the components of the motor can tolerate before being damaged. If the existing design is at all optimized, then you are...
  20. DickDV

    Siemens Sinamics G120 with BOP Fixed Frequencies

    You have to set up enough digital inputs for the speeds you need. For three speeds, you need two inputs; for seven, you need three; for fifteen, you need four. It may be that, if you don't have enough inputs assigned, the extra software is blocked out and skipped over.

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