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  1. #11
    Quote Originally Posted by m_c View Post
    It may be down to how each machine is connected. Do you have this machine connected, so the two legs (2 & 3) that power the control circuits, are connected to the non-generated leg on the converter?
    I will find the Transwave manual and have a look, do you mean L2 and L3 on the drawing?

    Quote Originally Posted by m_c View Post

    With most common single to three phase converters, two legs are supplied directly from a step-up transformer, then the 3rd leg is generated using purely capacitors (in the case of static converters), or by a combination of idler motor and capacitors (in the case of rotary converters).
    If you connect one of the control legs to the generated leg, then it is very likely to sag under motor starting loads, which would explain your symptoms. If you have had it connected this way, then there is a possibility that converter is the problem, which is why we're asking about voltages. It could be the converter has either developed a fault (some will try and boost the voltage under high load conditions), or it could just be a combination of capacitors getting a bit weaker as they age, a bit extra load on the motors, and the cold weather making things a bit sluggish, that have pushed things to the point the problem has become apparent.

    And if your other machines are connected so their control circuits are powered from the non-generated legs, it would give the impression the convertor is working fine, as although the generate leg would sag while starting, you probably would not notice any difference unless really pushing the machines to their maximum loads.

    So in short, check what voltages you're getting into the control, especially the voltage at the transformer that is supplying the 230V for the controls.
    So using test meter on Hv setting I get 237v on a workshop socket outlet (just checking I'v got the correct range) then 160v over the low side of the transformer and 364v over the high
    side. 160v seems too low?

    The contacts made well some times and chatterd others. Going to look for manual for Transwave.

  2. #12
    I was taught that 'rule' no1 when fault finding is, "check the supply"

    A contactor needs more voltage to close than it does to retain but 160v is only about 70% of required, plus, as the motor applies load it is going to drop a lot further.

    The other to watch is phase rotation, you don't want to be swapping phases around willy-nilly otherwise the motor direction could reverse.
    Last edited by EddyCurrent; 03-12-2017 at 01:59 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  3. #13
    You should test a supply in both no load conditions and with a load of a significant percentage of that with which you are having problems.
    You think that's too expensive? You're not a Model Engineer are you? :D

  4. #14
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 9-10 years. Has a total post count of 2,069. Received thanks 231 times, giving thanks to others 5 times.
    160V does seem low. It's not unknown for transformers to fail, but as Nick says, check what happens to the voltages when you try starting the motors. Test the high and low sides to see what happens.

    Also test between the other legs when starting, to see if you any sag more.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  5. #15
    Quote Originally Posted by magicniner View Post
    You should test a supply in both no load conditions and with a load of a significant percentage of that with which you are having problems.
    No desire to be pedantic about this but,
    That's not what I meant about 'rule no1' , I meant if there was nothing there when you pressed "start". In other words, "check there is the required voltage at the machine".
    The quality of the supply comes later after pressing "start" does it's job.
    Last edited by EddyCurrent; 03-12-2017 at 03:29 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  6. #16
    Sorry but I made a mistake when testing the voltage on the transformer, wrong connections.
    Now get readings of 464v and 260v.
    Also get 242v over the contactor.

    What to check next?

  7. #17
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 9-10 years. Has a total post count of 2,069. Received thanks 231 times, giving thanks to others 5 times.
    What happens to the voltages while the motors are starting, and the contactor chattering?
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  8. #18
    Quote Originally Posted by m_c View Post
    What happens to the voltages while the motors are starting, and the contactor chattering?
    From putting the meter over A1, A2 on the contactor and pressing the start button the voltage is not instant ie it climbs to 240v while it chatters,
    same if you put it over any of the other contacts. When it pulls in it is 240v. So readings might be 50, 70, 130, 170 then 240v (all while chattering)

    Is there a way of wiring out the braking board item 7 on the drawing and still making the machine work to eliminate it from being the problem?
    I can disconnect wire 24 from the contactor to stop it breaking, but there are 5 other wires still connected.

    Then I can happily spend the 500 knowing that that is the cause.

  9. #19
    Testing is not proceeding in a logical manner.

    Personally, I would install the original contactor first.
    With the machine disconnected from supply, manually operate the contactor and confirm, using an ohmmeter, that all the contacts operate as expected.
    Then I would remove the load, i.e. disconnect the selected motor, e.g. saw
    Plug the machine in and press start and see if the contactor pulls in and holds
    Now with a voltmeter I would test to see if we are getting 3 phases (full voltage) at the disconnected motor leads.
    If not, I would start at the supply end and work my way through to find the reason.
    If yes, then it suggests the wiring and contacts are okay, on no load at least.
    If you then press stop, there should be DC across 2 of the motor wires for several seconds (it makes a loud humming noise under normal conditions)

    If your machine works in a similar way to mine, if an e/stop button is pressed and you press 'start', then the braking system energises for several seconds just as during a normal stop.
    This means that if the contactor, and it's contacts, are not working correctly it may be possible to initiate the brake during startup. This is the main reason
    I would refit the original contactor and auxilliary as there may be some time delay involved here.
    The drawing is one of the worst I've seen and it's not easy, for me anyway, to determine exactly what's going on, and I've used some complex drawing in the past.

    I've attached a copy of the single phase version if it helps sort this out, (not studied it yet though)
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by EddyCurrent; 04-12-2017 at 09:55 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  10. #20
    Quote Originally Posted by EddyCurrent View Post
    No desire to be pedantic about this but,
    That's not what I meant about 'rule no1' , I meant if there was nothing there when you pressed "start". In other words, "check there is the required voltage at the machine".
    The quality of the supply comes later after pressing "start" does it's job.
    If I'd been referring to your suggestions I'd have quoted you.
    When looking for the source of a fault in a 3 phase electrical system where components such relays and actuators are commonly run from one phase with different components running from different phases then if you don't check what you have before applying any load at all then you can make things harder for yourself.
    Just saying ;-)
    You think that's too expensive? You're not a Model Engineer are you? :D

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