Search Results - Practical Machinist - Largest Manufacturing Technology Forum on the Web
Close
Login to Your Account

Search:

Type: Posts; User: SomeoneSomewhere

Search: Search took 0.00 seconds.

  1. Replies
    3
    Views
    233

    Most VFDs specifically allow you to do this. ...

    Most VFDs specifically allow you to do this.

    You need individual overload protection on each motor, though. The VFD can't detect over-current because it can only measure total current.

    Check...
  2. Replies
    126
    Views
    4,847

    So why does every new freight loco use AC...

    So why does every new freight loco use AC traction, with approx twice the starting torque for a similar size/weight/HP machine?

    Likewise, look at where there are new series universal or DC motors...
  3. Replies
    126
    Views
    4,847

    Yeah, but that generally requires drawing the...

    Yeah, but that generally requires drawing the corresponding 4x full load current from the supply as well.
  4. With larger permanent split motors, an option is...

    With larger permanent split motors, an option is to only put the speed controller/soft starter on the main winding, and not on the auxiliary/start. That way the capacitor doesn't see the nasty...
  5. Replies
    126
    Views
    4,847

    What I was taught in sparkie school is that with...

    What I was taught in sparkie school is that with reduced voltage mains frequency starters (primary resistance, autotransformer, star/delta, electronic etc.), your starting torque is proportional to...
  6. If you use 480 to 120/240, those panels will be...

    If you use 480 to 120/240, those panels will be fed off single phase. That means that your incoming 480V will be less evenly loaded.

    Whether that's an issue will vary.
  7. Replies
    4
    Views
    358

    I think that is one of the Huanyang units listed...

    I think that is one of the Huanyang units listed in the sticky as being banned from discussion.

    I would want a half-decent manufacturer for the output part; the input part is less critical. Most...
  8. Replies
    4
    Views
    358

    Some chinese manufacturers make a...

    Some chinese manufacturers make a rectifier-and-capacitor voltage doubler that can then be used to feed the DC link on a higher voltage VFD. This also allows you to use a VFD without derating for...
  9. Replies
    10
    Views
    730

    You do not need to connect the neutral, whether...

    You do not need to connect the neutral, whether or not it has ground-fault protection.
  10. If you're sizing VFDs for a compressor, you need...

    If you're sizing VFDs for a compressor, you need to use the 'high overload' rating, not the 'low overload'/'HVAC' rating. They need more starting torque for longer and the running torque doesn't back...
  11. The older current-source units I believe really...

    The older current-source units I believe really didn't like it, as you essentially had a big fat inductor in the DC link and then suddenly stopped the current flowing through it. Big voltage spike.
    ...
  12. 30A inrush isn't super uncommon. Many LED drivers...

    30A inrush isn't super uncommon. Many LED drivers will draw that if you give them enough fault current to play with. Capacitor charging is brutal.
  13. Replies
    12
    Views
    1,005

    Most 230V motors have a 'usable at 208V' rating...

    Most 230V motors have a 'usable at 208V' rating from what I can see. I imagine doubling this to 416V would be about right for a 460V motor.

    You lose a little available power with the lower...
  14. Is it three phase 230V line to line, or three...

    Is it three phase 230V line to line, or three phase 230V line to neutral?

    If the latter, then the line to line voltage will be 400V which is too much for your supply - you need either a 400V input...
  15. VFD phase loss fault...

    VFD phase loss fault

    This (and a handful of other sources) suggests that phase loss prevention generally looks at ripple on the DC bus.

    Even if the VFD was looking for voltage presence on each...
  16. Given your transformers are connected...

    Given your transformers are connected delta-delta, I wonder if one of the windings is reversed. That would mean it's essentially trying to drive into a short circuit.

    Try disconnecting one of the...
  17. You can bury the VSD and still use the existing...

    You can bury the VSD and still use the existing controls.

    What you need to do is disconnect all the existing wiring from the controls and hook the motor up to the VFD output directly, possibly...
  18. Can we get VFD models, motor dataplate, and what...

    Can we get VFD models, motor dataplate, and what your supply is?

    As above, you need to not open or close any switches between the VFD and motor under load. The motor needs to be connected to the...
  19. Replies
    10
    Views
    1,076

    It's not exactly verboten to have switches,...

    It's not exactly verboten to have switches, contactors, or plugs/sockets between a VFD and the motor, but it's best not to open them under load (especially with older drives), and definitely don't...
Results 1 to 19 of 19