10EE with solid state DC drive - how to add reverse circuit and ELSR - Page 2
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  1. #21
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    Quote Originally Posted by Colt45 View Post
    Hi Bill
    Have a single quadrant DC drive (MP25A4) here on the bench- could you elaborate a bit on this? Would appreciate any suggestions about setting up mechanical contactors for reversing (SquareD 8702s with interlock) and also adding braking resistors.
    Great drive, and serious overkill, so you have a comfortable reserve. But...at about double - or more than double - the new price of the 4Q Parker-SSD's. Not as common, used, either, so...

    Issues - spikes & c. - I cautioned about come up with drives made by folks who don't have the "deep pockets" for R&D, nor the experience - especially with the higher-voltage drives (above 180 VDC) that Europe commonly uses.

    No fear. Control Techniques have already protected this drive for yah.

    As a 1Q drive, external contactor reversing is one of the expected situations, as are braking resistors.

    That should all be in the manual. Do it "by THEIR book" (not mine!) and yer good to go, and should last a long time.

    HTH

    PS: About that "overkill" thing...

    "For my next trick".. since I have more fun making tests and experiments rather than chips.. I'm looking at nicer contactors for machines that do NOT have 4Q drives. MG, ( I hve kept one in the OEM state) ...WiaD, Modular, 1Q Solid-sate....

    Pull yerself the spec sheet on the Gigavac HX22 series. Not vacuum, but hermetically sealed, so no arcy-sparky. See whatcha think.


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    Quote Originally Posted by thermite View Post
    At normal max Armature voltage the 3 HP large frame, installed and belted to a spindle, will not reach stratospheric "squirrel cage" RPM, even with ZERO field.

    There's too much drag. The strength of residual magnetism is degraded too soon. There's ample time for an operator to shut-down the Armature supply as well.
    In any case, if people keep the original system and don't throw away all the features that Monarch went to a lot of trouble to include, they will have the field loss relay to shut it down automatically.

    Re replacing the MG with a solid state supply, that makes some sense but you should keep the original control system and not have to ask questions like "How can I reverse it?" You may need some strategically placed MOVs and inductors to protect the transistors. The conversions I have seen get the spindle to run but lose all the fine points.

    The field supply needs to be regulated, also. I see so many where the exciter has failed and they put in a simple bridge rectifier. The field supply needs to be steady for the spindle speed to regulate properly. This is not speculation- I coupled a 5 hp DC motor to the spindle for a dynamometer and experimented with supplies. By varying its field current, I could apply any load from almost 0 to full. If the field supply varies with load, the RPM will not be constant.

    Re solid state supplies, I worked on the system supplying the trains running around in Peabody's No 10 coal mine near Springfield, IL. They had 15 miles of tunnel underground with one half supplied by "modern" solid state supplies and the other half by motor generator sets. The MGs ran on 4160 three phase and output 300 VDC, up to a half megawatt each. Despite having to do routine maintenance like changing oil in the bearings and replacing brushes, the miners much preferred the MGs because they were more reliable. The two systems had to be separated, each supplying half the overhead trolley wires because the MGs would blow up the transistors. Of course, when a contactor carrying 1000 amps opens, it generated a righteous spike.

    Likewise the platers in Rock Island Arsenal. The world had switch over to solid state, but they preferred MGs, again for reliability.

    Bill

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    Quote Originally Posted by Colt45 View Post
    Would be great to see your set up- did you do anything special to address potential issues with the SCRs? Interlocks, timers, braking resistors?
    Bill's relays - and others using ELSR, as Mark did as well - put small relays on the low-power CONTROL side of the 4Q drives.

    No problem. 1Q, 4Q, or other, all those inputs were built with pretty good noise-immunity already.

    Control side or power side - all the major makers have also TESTED this stuff and put it in their manuals.

    After all the research I did, the main lesson was "RTFM". Seriously.

    Even the need of a choke/ripple-filter was published by both the DC Drive maker AND Reliance, the motor maker.

    Dunno how we missed that as often as the community had done, what with the old "PRE "Rectified Power / Inverter Duty" motors growling at us without it?

    For those who have not (yet) had "the pleasure"?

    Add $275/$300 worth of 20 Amp 20 milliHenry Hammond choke, and the MOTOR goes really quiet, even on acceleration, should live a lot longer.

    The CHOKE then does the growling on hard acccel, but harmlessly, and much less of it. I use a small choke on the 507 field supply as well, BTW.

    "RTFM" again. Even the newer "RPM" (Rectified Power Motor" specs a ripple filter in all windings above 180 VDC.

    Mind.. "the manual" - any major maker - covers all kinds of applications, so it takes some work - I estimate reading it five times and taking notes - to sort out which two or three percent of the whole damned book is all that your particular use needs!

    Could be worse, I guess?

    Some folks restore B-29 bombers for a hobby!



    Mind .. now that the rest of you lot have taken up THIS solution?

    I can get back to work on my faster-than-light starship drive.


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    The Mentor manuals are easy to read and pretty thorough, but do not describe using a contactor for reversing, nor the implementation for braking resistors.
    Do you mean to install the choke on the output of the drive?

    Thanks for your responses, those Gigavac contactors look really nice.

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    Quote Originally Posted by Colt45 View Post
    The Mentor manuals are easy to read and pretty thorough, but do not describe using a contactor for reversing, nor the implementation for braking resistors.
    There is a second level of manuals. Heavier stuff for use of Design Engineer "adopters" / Decision-Makers as to application "design win" support.

    Seriously well detailed, those are.

    Busy now. Not sure I have a copy and it would be on a seldom used older 'puter if I do have it.

    Do you mean to install the choke on the output of the drive?
    Yes. In series with the Armature leads for the BIG one. My "best one" uses a German-wound Lenze "swinging" or load-reacting choke, but those goods are no longer to be found.

    In series with the Field leads for the small one. I'll have to look in my files as I've trialed 3 different ones.

    Polarity doesn't matter.

    Polarity CAN matter if one applies the REST OF the Yaskawa/Magnetek white-paper on the "quiet elevator" scheme.

    I tested that with a bunch of 440 V rated "run" caps.

    Adding the caps made the rig quieter, yet, just as Yaskawa claimed.

    Given that a machine shop is not ordinarily a silent place, it wasn't really ENOUGH quieter to be adding caps.

    They simply don't last as long as chokes do.


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