Major Frustration

This is not going to be a long blog post, primarily because the day ended with a similar result to the day before, but with far more confusion! We managed to get everything operational, but unless we imposed a very odd set of instructions to the car’s components, not everything would work simultaneously. For example, the car starts up fine with either of the 2 motor controllers connected, but not when they were both connected at the same time. This behaviour has not been seen before and raises some very peculiar questions.

So we ended up spending over 13 hours working non stop to try and find the problem, but after checking every component, using an oscilloscope to measure wave forms of the signals down to the microsecond level, we still could not find the problem. Fortunately, Javier, an electronic engineering professor here at the university dropped in not only with his knowledge, but also some delicious pizza which kept us going long into the night! At least that kept our spirits up, because the last thing you want to be is hungry as well as tired while working on the car!

It would take a long time for me to explain the car’s system to help properly explain the issues we are seeing, but as usual, we’re working round the clock to get it fixed! I hope to be able to give you all some good news soon though…wish us luck!

4 Responses to “Major Frustration”

  • Charles H Schulmann says:

    Dear RGET ,
    we really feel for you guys and we certainly wish
    you the best of luck that you zero on the cause
    of this infuriating mystery .
    However , we would be derelict of our support for you
    if we did not at least suggest some form of half intelligent
    remedy – half because none of us are physically ,
    there with you and nor were we there when you built
    the SRzero , neither do we claim to have any answers ,
    so , please do not be irritated if you have already done ,
    what we might suggest .

    We presume that , the management systems are somehow not
    receiving the right data feedback as you have to impose
    an odd set of instructions .

    Do the outputs ( voltage or current ) from the management
    system for the relevant set of instructions correspond
    with the expected values and do the feedback inputs also
    correspond ?
    Example: In our case , we have dc drive control cards
    which control our pumps driven by dc motors and it has
    happened that the cards for various reasons have had to
    be recalibrated so that the output of the control card
    corresponds with the expected speed of the dc motor ,
    while the feedback from the dc motor’s tacho-generator
    is misinterpreted by the dc control card which results
    in terrible speed fluctuations .

    Using this example , we are forced to ISOLATE (time
    consuming but successful ) each system to test their
    integrity in terms of INPUT DATA as well as their
    corresponding OUTPUT DATA and vice versa where input
    is dependant on output .
    There are three pumps which have to work in pairs at
    different ratios at different times which are controlled
    by a management system whose output ( 1 – 10 volts ) to
    the respective dc cards have to instruct the cards to
    provide the correct dc drive output voltages ( 0 –200 volts )
    on condition that the tacho-generators are synchronized .
    Yes , I know it is rather convoluted , but works like a charm
    when all the different elements of the system are synchronized .

    Now as it has been reported earlier in another post ,on one
    occasion the control cards of that system which successfully
    shut down due to a fire , was nevertheless compromised because
    the fire had altered the electrical properties of some the power
    semi conductors and electronic components .
    While the damage was minimal in terms of the installation ,
    the control had to nevertheless be examined thoroughly in
    isolation with a number of electronic component changes .

    We hope that , this may offer a glimpse of a solution and that
    you discover and repair the problem .

    We wish you all the best in your endeavours from
    Ladysmith ( Kwazulu Natal ) in windy South Africa ,
    Charles and friends .

  • Gordon Glatz says:

    Does the contactor use a seperate set of contacts (Part of the contactor)in the coil circuit that closes with the contactor to seal it. If those contacts are dirty, pitted, or burnt where they are not passing current, The Contactor will close but not remain closed. Like wise there must be a normally closed contact in the same coil circuit controled by the what ever opens the contactor to shut it down. If either of these are working the contactor will not remain closed.

  • Gordon Hamm says:

    Have you checked the current draw of the motors under load? Are they drawing the proper current as per their specs?
    The way you are explaining your controls, the tacho generator is on the output shaft of your drive motors, if you have a bearing problem in one of your motors or if a bearing in your wheel is gone, it is going to affect the rpm of the drive motor which in turn is going to affect the output of the tacho generator. Which in turn the control circuit is going to apply more voltage and more current to compensate. Am I correct?

  • Gordon Glatz says:

    Typo in last line, should read, “If either of these are NOT working the contactor will not remain closed.”

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