what does the exciter do on a 10ee MG?
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    Default what does the exciter do on a 10ee MG?

    i just got a 10ee round dial MG with a DC power supply hooked right into the exciter terminal box. The dc supply is delivering 86.27volts DC. So far I have the spindle running in both directions up to about 2200 rpm. Can anyone explain the function of the exciter?
    Spindle motor will not operate unless the dc power supply is on.
    Does the exciter still need to be spinning via the belt if there is DC voltage coming from elsewhere?

    thanks
    Rich

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    Quote Originally Posted by lectrician1 View Post
    i just got a 10ee round dial MG with a DC power supply hooked right into the exciter terminal box. The dc supply is delivering 86.27volts DC. So far I have the spindle running in both directions up to about 2200 rpm. Can anyone explain the function of the exciter?
    Spindle motor will not operate unless the dc power supply is on.
    Does the exciter still need to be spinning via the belt if there is DC voltage coming from elsewhere?

    thanks
    Rich
    If you have an add-on DC supply it's probably because the exciter failed. You can take the belt of an just leave it there.

    The exciter provides power for three things: 1) the DC control panel, 2) the spindle motor's field, and 3) the DC generator's field. The big pair of Ohmite rheostats vary the voltage provided by the exciter to the spindle motor and generator fields to provide the variable speed "magic". One rheostat ramps up the voltage to the generator's field, causing it to increase its output voltage, which is provided to the spindle motor's armature. The other rheostat then kicks in to reduce the voltage to the spindle motor's field, weakening the field and causing the motor to run faster.

    Cal

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    Thank you Cal! Next question is should the voltage be closer to 90v. Dc from the supply? I am wondering if the power supply voltage has anything to do with the spindle motor not reaching 2500rpm. Thank you very much for your help
    Rich

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    Quote Originally Posted by lectrician1 View Post
    Thank you Cal! Next question is should the voltage be closer to 90v. Dc from the supply? I am wondering if the power supply voltage has anything to do with the spindle motor not reaching 2500rpm. Thank you very much for your help
    Rich
    The exciter puts out 115 VDC, but around 90 VDC is about as well as you're going to do with a simple rectifier. If the generator's field doesn't get full voltage, it won't put out full voltage to the spindle motor, so it will definitely keep the motor from reaching full speed. Some exciter replacement circuits include a small boost transformer to pump up the input to the rectifier enough that it puts out 115 VDC. And depending on what type of meter you have, the DC waveform may be fooling the meter and not giving you an accurate voltage value.

    Cal

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    how many amps does the exciter supply? or how many amps should my new power supply be rated at? i would like the machine to be able to operate at 2500rpm. or would it be easier to find another exciter?

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    I have never worked on a round dial, so this isn't gospel, but in my experiments with a square dial with a Reliance MG the speed vs load characteristics were much better with a regulated supply. They are pricey new but they often show up in surplus stores at low prices. They also have the advantage that you can set the voltage to suit.

    Bill

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    I noticed on a generator/exciter for sale on ebay that the amperage is 2.4. I just ordered a chinese 120v DC variable power supply that can handle 3amps. It was cheap so i thought i would give it a try. I'll keep you posted on the results.
    Thanks for the assistance
    Rich

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    Quote Originally Posted by lectrician1 View Post
    I noticed on a generator/exciter for sale on ebay that the amperage is 2.4. I just ordered a chinese 120v DC variable power supply that can handle 3amps. It was cheap so i thought i would give it a try. I'll keep you posted on the results.
    Thanks for the assistance
    Rich
    That can work, and does work.

    But the exciter has another function. The final drive motor is straight-shunt, inherently good at self-regulation under load, but... even better, stability-wise, when assisted by some compensation.

    Which is built into... ta da.. that otherwise curiously oversized exciter, providing as it does field power to BOTH the primary DC generator AND the final drive motor.

    More "elegant" an overall system than first appears, in other words.

    Parker-SSD 506, 507, 508 1Q DC Drives at anywhere from $25 to $80, used-but-good, can be run in "current" mode, have lots of upper/lower limit, up/down ramp-rate, sensitivity and stability optioning to provide neat and tidy DC out @ 115 VDC. Or even max @ 140 VDC as I run my ones for improved torque to extend the lower RPM range. This application, 230 VAC-in, max 180 VDC out KB-Penta, Minarik, Danfoss-Graham, Dart, etc. - most any small-HP DC Drive dialed-down to 115 VDC will be much the same.

    'Scope might show the Chinese one with worse ripple? Probably.
    But "she'll do" chip-making-wise.

    If there is so much AC ripple as to create annoying buzzing of the field coils? Just slap a decent choke of adequate Ampacity in series with each field and she'll go quietly. No need of caps. They age too badly to be worth the bother. Chokes are near-as-dammit "immortal" by comparison, so...

    2CW

    PS: Neither the MG "main" DC generator for the Armature power, nor an OEM exciter need a ripple-filter choke.

    "Rotating Power" DC is right close to a variable-voltage battery for smooth output. 'Scope it and see. Insignificant amount of brush noise is about all.

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    thanks Thermite
    i just bought a parker ssd 506 on ebay used for $70 as per your suggestion.
    i will try both the parker and the chinese one and see which works best

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    Quote Originally Posted by lectrician1 View Post
    thanks Thermite
    i just bought a parker ssd 506 on ebay used for $70 as per your suggestion.
    i will try both the parker and the chinese one and see which works best
    For "1Q", the Parker 5XX series are nicely executed, but not necessarily any better than any OTHER decent DC Drive.

    I went that route primarily because the alarm and control signals are fully compatible with its bigger brother - the 4Q SSD 514C-16 I use for the Armature supply.

    That made control interface and use of alarm or other signals off one to manage the other far easier, eliminated having to DIY "stuff" they already had on-PCB and terminal strip - test and commissioning terminals included, of course. A 514C-16 even has handy "inverse" outputs. over-rides, RPM, load percentage, tacho sharing, and such already presented.

    Flexible bugger. TOO flexible, given it takes about five head-scratching and note-taking runs through the manual to end up realizing .... one basically leaves it TF alone at sensible defaults!



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