Potentiometer

  1. daleyd

    daleyd Member

    Messages:
    6,881
    Location:
    Wrexham, North Wales
    It will matter to “some” drives that’s why they specify what you can use (eg if it. asked for a 5k max and you fitted 10k you might not get the full speed range) - they use the voltage drop across the resistor to calculate span, and the wiper is the setpoint - but in this case it looks like the right one is fitted anyway.
     
  2. Seadog

    Seadog Forum Supporter

    Messages:
    6,549
    Location:
    NE London - UK
    You will need all three wires connected or it will not function correctly.
     
  3. hunter27

    hunter27 Pete

    Messages:
    590
    Location:
    Lancashire UK
    There are 3 wires connected to the pot, 1 with a grey tag and one with a brown tag and one wire un-tagged (I think it should be a green tag and it seems to loop round a safety circuit of the backgear knob, the carriage stop switch and the change wheel casing switch). At the inverter the grey and brown tie up with 8 and 11 but there is nothing in 12.
    I have had the lathe for probably 3 years now with no trouble and I haven't altered anything.
    inverter connections.jpg
    Will see what happens when the pot turns up.
    Cheers Pete
     
  4. Seadog

    Seadog Forum Supporter

    Messages:
    6,549
    Location:
    NE London - UK
    If you don't have the three wires connected it'll be more liable to noise pickup.
     
  5. hunter27

    hunter27 Pete

    Messages:
    590
    Location:
    Lancashire UK
    I will try the pot when it comes and if that works I may use one of the spare wires to run the unmarked pot wire directly back to inverter No 12. At the moment it appears to be indirectly connected to 5 terminal via the safety micro switches?
     
  6. hunter27

    hunter27 Pete

    Messages:
    590
    Location:
    Lancashire UK
    Update
    Bad news. The new pot came but made no difference! I also tried wiring it directly to the inverter on short tails to prove the wiring was okay and also with the pots ground wire to No 12 terminal instead of how it has always been wired all without any improvement. The lathe still runs without any wires in the pots connections.
    I have re fitted the old pot and Emailed IMO to see if I can get an instruction book for it.
    Fingers crossed
     
  7. Seadog

    Seadog Forum Supporter

    Messages:
    6,549
    Location:
    NE London - UK
    If it's running without the pot, then surely the configuration has been altered to have a set motor speed.
     
  8. hunter27

    hunter27 Pete

    Messages:
    590
    Location:
    Lancashire UK
    There is a led display that states ready when powered up then when I start the lathe it changes to numbers around 35 that gradually creep up to 40. There is also a Mode button a up button and a down button.
    inverter.jpg
    This is all in a closed cabinet that had been untouched for ages until after the problem occurred. I am a bit worried about upsetting the programming without instructions. I have tried pressing up and down buttons nothing happens, pressing Mode goes to PR 0 (already set at 15) then other numbers which mean nothing. I will see if the manufacturers come back to me
    Cheers Pete
     
  9. RichardM Member

  10. hunter27

    hunter27 Pete

    Messages:
    590
    Location:
    Lancashire UK
    Thanks RichardM
    It's not quite the same model (mine is a CUB. CDS and has a red LED display with a mode button and up and down keys on the front) but is the nearest to it I have seen it and looks very similar including the wiring diagram.
    I will save it on my computer and have a good read.
    Thanks again
    Pete
     
  11. hunter27

    hunter27 Pete

    Messages:
    590
    Location:
    Lancashire UK
    Update
    Today IMO helpfully sent me a PDF of the instruction manual for my 20 year old inverter so I now have a slightly better understanding of what's going on.
    I think the fault is with the inverter itself , I have set all the parameters to the default settings and have re-tried the old pot and the new one but it makes no difference to the speed. Even with no wires in the pot connections on the inverter it still runs at medium speed.
    The motor is a 3 phase Crompton 3/4Hp 1425Rpm 50Hz and the lathe spindle should achieve 1400Rpm. Flat out on the correct pulleys I can get just below 600Rpm and it is not happy starting rotating at that.
    If I can't think of anything else to try in the next few days I will ask an electrical friend to take a look at it for me or look for a single phase motor for it.
    Thanks for all your replies.
    Pete
     
  12. MBB Forum Supporter

    Messages:
    1,067
    Location:
    northumberland
    On page 9 of the manual you will see 4 pots, max speed, min speed, ramp up, ramp down. adjust the max and min pots to suit set the min at bottom.
    Set max to what you want.
     
    hunter27 likes this.
  13. hunter27

    hunter27 Pete

    Messages:
    590
    Location:
    Lancashire UK
    The instructions book PDF looks like it is made up from lots of different books and there is no page 9 in it.

    I noticed that in Pr A (trip codes) it says UU, in the book it says UU means 'the internal power supply voltage has fallen below the operating range' or 'UU trip can also be caused by a failure of internal components of the drive' these conditions require expert attention. Please consult your supplier.

    The helpful chap at IMO later Emailed me back to ask what the problem was and I have passed on this info to him. This inverter is no longer supported though.
    Cheers Pete
     
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