Page 3 of 5 FirstFirst 12345 LastLast
Results 31 to 45 of 69
  1. #31
    Join Date
    Apr 2009
    Location
    Horsham
    Posts
    89

    Default

    Just checked and it looks like I've been duped... Oh well...

    20150617_172422-800.jpg20150617_172604-800.jpg

  2. # ADS
    Google Adsense Advertisement
    Join Date
    Always
    Location
    Advertising world
    Posts
    Many





     
  3. #32
    Join Date
    Jun 2005
    Location
    Helensburgh
    Posts
    6,951

    Default

    Quote Originally Posted by Jayson View Post
    Just checked and it looks like I've been duped... Oh well...

    20150617_172422-800.jpg20150617_172604-800.jpg
    Stand by, I have contacts at Powtran. I will send them an email now and see what the reaction is.

  4. #33
    Join Date
    Apr 2009
    Location
    Horsham
    Posts
    89

    Default

    Hi Chris,

    Mine wasn't from Powtran. It is a Huanyang VFD

  5. #34
    Join Date
    Jun 2005
    Location
    Helensburgh
    Posts
    6,951

    Default

    No worries.

  6. #35
    Join Date
    Oct 2006
    Location
    Armidale NSW
    Age
    50
    Posts
    1,938

    Default

    Quote Originally Posted by Jayson View Post
    Just checked and it looks like I've been duped... Oh well...
    Maybe it's just an issue with your multimeter? Are you running it at over/around 100hz?
    Cheers.

    Vernon.
    __________________________________________________
    Bite off more than you can chew and then chew like crazy.

  7. #36
    Join Date
    Aug 2007
    Location
    Melbourne
    Age
    66
    Posts
    1,417

    Default

    Quote Originally Posted by Jayson View Post
    Just checked and it looks like I've been duped... Oh well...

    20150617_172422-800.jpg20150617_172604-800.jpg
    But you cannot measure VFD output voltage with a digital multimeter. Even if that multimeter was a true RMS tye, it would just show meaningless garbage figures, due to its limited bandwidth and the RF noise created by the VFD. The VFD output is a non-sinusoidal, pulse width modulated voltage of several kHz frequency. That meter you have there may show a voltage easily 50% higher than it is in reality. To measure VFD output voltage you need an oscilloscope, or a very specialized digital multimeter. Or in a pinch you can use an old analog multimeter, but it has to be one with very low Ohm per Volt impedance (less thn 20 KOhm/Volt) else it will not be much better than a digital multimeter. If you have an oscilloscope, that would be your best option. If you are not into electronics or do not have a mate that is and do not want to spend 1k$+ on suitable measuring equipment, it is fair to say that the output voltage of a VFD cannot be measured at all.

    What you could measure with that multimeter you have is the DC bus voltage, and that would be about 1.41 times the input voltage. But again, if you are not into power electronics it may be a bad idea to try this, as the bus voltage would have to be accessed inside the VFD. One false move and it starts getting life threatening. Not long ago we had a suicide candidate guy that was testing the board of a DC variable speed controller on a steel benchtop..... most fortunately he only cooked the board..... and not himself.

  8. #37
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    25,622

    Default

    Quote Originally Posted by cba_melbourne View Post
    But you cannot measure VFD output voltage with a digital multimeter. Even if that multimeter was a true RMS tye, it would just show meaningless garbage figures, due to its limited bandwidth and the RF noise created by the VFD. The VFD output is a non-sinusoidal, pulse width modulated voltage of several kHz frequency. That meter you have there may show a voltage easily 50% higher than it is in reality. To measure VFD output voltage you need an oscilloscope, or a very specialized digital multimeter. Or in a pinch you can use an old analog multimeter, but it has to be one with very low Ohm per Volt impedance (less thn 20 KOhm/Volt) else it will not be much better than a digital multimeter. If you have an oscilloscope, that would be your best option. If you are not into electronics or do not have a mate that is and do not want to spend 1k$+ on suitable measuring equipment, it is fair to say that the output voltage of a VFD cannot be measured at all.
    Many CRO's don't have sufficient V/division to reach mains power V's levels.

  9. #38
    Join Date
    Aug 2007
    Location
    Melbourne
    Age
    66
    Posts
    1,417

    Default

    Quote Originally Posted by BobL View Post
    Many CRO's don't have sufficient V/division to reach mains power V's levels.
    Bob, that is correct. That is why they make 10:1 and 100:1 and 1000:1 probes to go with scopes.

    If you take a scope with a maximum of 5V/division, and add a 10:1 probe, it becomes 50V per division. With 10 divisionss on the screen, you can display a full 250V sine curve, going 250V positive to 250V negative. If you add a 100:1 probe, each division becomes 500V. There are switchable probes too, so you do not have to buy 2 or 3 probes.

    Be careful with scopes that do not have fully insulated input stages when measuring VFD outputs, you may end up with line voltage on the scope chassis. Fully insulated handheld scopes are the ideal tool to work on VFD's.

  10. #39
    Join Date
    Aug 2007
    Location
    Melbourne
    Age
    66
    Posts
    1,417

    Default

    Quote Originally Posted by BobL View Post
    Many CRO's don't have sufficient V/division to reach mains power V's levels.
    Bob, that is correct. That is why they make 10:1 and 100:1 and 1000:1 probes to go with scopes.

    If you take a scope with a maximum of 5V/division, and add a 10:1 probe, it becomes 50V per division. With 10 divisionss on the screen, you can display a full 250V sine curve, going 250V positive to 250V negative. If you add a 100:1 probe, each division becomes 500V. There are switchable probes too, so you do not have to buy 2 probes - like this one, the longish black slider selects between 1:1 and 10:1
    switchable_probe.jpg

    Be careful with scopes that do not have fully insulated input stages when measuring VFD outputs, you may end up with line voltage on the scope chassis. Fully insulated handheld scopes are the ideal tool to work on VFD's.

  11. #40
    Join Date
    Apr 2009
    Location
    Horsham
    Posts
    89

    Default

    I just borrowed a mates new DSO and went to measure the voltage, turned on the VFD, hooked up the little alligator clip to one of the phases and boom, flash, #$#@....

    Pointing my friend to this thread so he can see it wasn't my fault......

    Lots of information has been given in this thread that could result in the above.

    So, lets just leave it at no VFD will give 380/415 output from 240 in, this seems to be the consensus from those that know.

    Going out to the shed to use my lathe...

  12. #41
    Join Date
    Jun 2010
    Location
    Canberra
    Posts
    769

    Default

    Quote Originally Posted by cba_melbourne View Post
    Be careful with scopes that do not have fully insulated input stages when measuring VFD outputs, you may end up with line voltage on the scope chassis. Fully insulated handheld scopes are the ideal tool to work on VFD's.
    Honestly, you'd want to be pretty brave/competent to go scoping the output of a VFD - for starters, the output is probably floating, meaning you really want to differential probe across 2 scope channels (or use a differential probe), and even with 10:1 or 100:1 you really want a decent Cat rating on the probes - having a high divider ratio on a probe does *not* mean it's therefore designed for high voltages.

    I'd expect measuring the voltage with the load attached would go some way towards dealing with the harmonic content. Also I think the DC bus is sometimes readily available for connection to a braking resistor? Again, though, I'd be really careful measuring high DC voltages with a DVM that's not properly designed for high-energy sources.

  13. #42
    Join Date
    Jun 2010
    Location
    Canberra
    Posts
    769

    Default

    Quote Originally Posted by Jayson View Post
    So, lets just leave it at no VFD will give 380/415 output from 240 in, this seems to be the consensus from those that know.
    While I've never met one, there's no reason they can't exist, you'd just need an intermediate inverter stage (i.e. a DC-DC converter) to boost the DC bus voltage.

  14. #43
    Join Date
    Jul 2010
    Location
    Melbourne
    Posts
    7,775

    Default

    Quote Originally Posted by RustyArc View Post
    Honestly, you'd want to be pretty brave/competent
    I have a 20V/Div CRO with 10 times CAT 1 500V probes but I'm pretty sure it doesn't have isolated inputs and I'm neither brave or competent
    I assume 500v wouldn't really be considered good enough?
    If I had an isolation transformer large enough to run the VSD on would that remove the isolated input problem?
    Not that I have any plans to do such ATM just interested.

    Quote Originally Posted by Jayson View Post
    So, lets just leave it at no VFD will give 380/415 output from 240 in, this seems to be the consensus from those that know.
    Want to bet?

    Stuart

  15. #44
    Join Date
    Jul 2010
    Location
    Melbourne
    Posts
    7,775

    Default

    Quote Originally Posted by RustyArc View Post
    While I've never met one, there's no reason they can't exist, you'd just need an intermediate inverter stage (i.e. a DC-DC converter) to boost the DC bus voltage.
    I believe(though cant recall where I got the info from) that my VSD uses a voltage doubler* on the mains side then uses a standard 415V VSD.

    As I said earlier but have never put a meter on it...... but I have run the same motor on a 240V in/out VSD an you can certainly tell the difference.

    Stuart

    *If I recall correctly the person that supplied said info was not all that impressed with the design of said doubler, but so far it seems to be working just fine.

  16. #45
    Join Date
    Aug 2007
    Location
    Melbourne
    Age
    66
    Posts
    1,417

    Default

    Quote Originally Posted by Stustoys View Post
    I believe(though cant recall where I got the info from) that my VSD uses a voltage doubler* on the mains side then uses a standard 415V VSD.

    As I said earlier but have never put a meter on it...... but I have run the same motor on a 240V in/out VSD an you can certainly tell the difference.

    Stuart

    *If I recall correctly the person that supplied said info was not all that impressed with the design of said doubler, but so far it seems to be working just fine.

    Drives Direct in the UK sells a range of 240V to 415V inverters. They seem to use a voltage doubler at the input stage. Drives direct must have had them manufactured on order, as no one else seems to sell them. Here is a video that shows the insides. I think it is an earlier model, not exactly the ones they sell now:

    https://www.youtube.com/watch?v=VnLRhEHVLxA

    Towards the last third of the video, the drive is shown inside. At the top left is the voltage doubler stage, with the capacitors. The guy uses a Fluke 867B to measure the VFD voltages - that instrument is ideally suited for the task.

    Given the steep price of thes Drive Direct units, I wonder if it would not be cheaper to use a normal 400V input VFD and feed it from a 240V/400V step-up transformer up front.


    Here some good information on measuring (safely!!!) on VFD's:
    http://www.testequipmentdepot.com/ap...289-dmm_an.pdf
    http://en-us.fluke.com/community/flu...o-a-motor.html
    http://assets.fluke.com/AppNotes/Ele...r/GO416b_u.pdf

Page 3 of 5 FirstFirst 12345 LastLast

Similar Threads

  1. Tidying up a 3ph star-> delta conversion
    By RustyArc in forum ELECTRONICS
    Replies: 1
    Last Post: 27th Mar 2015, 09:44 PM
  2. Which way to connect a 3 phase motor?
    By Vernonv in forum METALWORK FORUM
    Replies: 6
    Last Post: 7th Sep 2014, 07:10 PM
  3. Converting 3 phase star to delta
    By simonl in forum METALWORK FORUM
    Replies: 36
    Last Post: 24th Oct 2012, 03:32 PM
  4. Star/Delta motor wiring
    By .RC. in forum METALWORK FORUM
    Replies: 33
    Last Post: 3rd Mar 2012, 11:01 PM
  5. Single pahse rewire multi-voltage motor - help needed
    By Too Many Clamps in forum TABLE SAWS & COMBINATIONS
    Replies: 6
    Last Post: 28th Jan 2011, 08:02 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •