Motor Generator Q

For general discussion with your fellow Minuteman III crewdogs, maintainers and cops. Currently based at Minot AFB, ND, Malmstrom AFB, MT, and F. E. Warren AFB, WY. Formerly based at Grand Forks AFB, ND. Operational from 17 Apr 1970 to present. Share your stories and meet up with an old friend.

Motor Generator Q

Postby Dav on Thu Sep 14, 2006 10:41 pm

Anyone an expert on the Motor Generator? Any EMT types?

We've recently had a question and subsequent training on the MG DC toggle switch, and the training going against the way I understand AC/DC stuff.

Bottom line was that they were saying that the DC system is tied into the AC system (before the generator part of the MG) and that without the DC system, the AC system would brown out over time. PM mee you have any idea what I'm talking about.
If you kill one, it is a tragedy...kill ten million? It is a statistic"
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Postby claw on Sun Oct 15, 2006 7:25 pm

Dav,

ron here. good to see you are still working hard up there. For further follow up, see steve bonin...he's pretty smart on that. This is what I know. If AC power is being applied to the MG (and hence on the AC motor), and if you turn the DC switch off, yes, the MG will eventually brown out since the switch also provides power to the exciter. An EMT guy explained this to me one day in the capsule. Any more than that, you'll have to seek steve or EMT out.

Hope all is well up there...BTW...when are you leaving? What you looking to do? Take care buddy.
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Postby Dav on Mon Oct 16, 2006 9:05 pm

I wonder what the time frame is for the exciter to power down? It was a while ago, but a crew got to experience a black capsule... from what I gather, the switch was off for quite some time before they had an LOPP and you know the rest.


I guess I see now, but I still dont see why they would design it that way.
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Postby Pappy on Mon Jan 29, 2007 1:17 am

Reaching way back here (78 to 82)
Note: Acronyms may be off here

How it works if I remember correctly is the DC brushes are held away from the MG commutator by AC power.

So you have 3 systems to keep your MG running; in this order
AC Commercial Primary Power (Normal) From Top Side
DC Battery Power (Emergency) Under your feet
AC Standby Power (Standby Diesel Generator) Next room over

What you don’t want are the DC brushes contacting the MG commutator when they are not in use as this will cause unnecessary wear and drain power from the batteries. (Kind of like running on both) Therefore when a Commercial Primary Power failure happens you won’t have enough DC Battery Power (emergency batteries) to keep the MG alive long enough for AC Standby Power (diesel generator) to take over the load.

Normal Scenario:
When you have an AC Commercial Primary Power failure the brushes drop on the commutator and the MG switches to DC Battery Power (emergency batteries) until the load can be picked up by the AC Standby Power (diesel generator) in the LCSB then your back on AC but it’s AC Standby Power (diesel generator) and the brushes should retract. AC Commercial Primary Power returns and takes control of the load, AC Standby Power (diesel generator) cools down and goes to sleep.

Not So Good Scenario:
Brushes have been down for an undetermined amount of time draining batteries. AC Commercial Primary Power fails, system transfers to DC Battery Power but not enough juice to hold out for AC Standby Power to get started up and take over load.
Then the Capsule gets dark, racks with seals get touched, ghost of long forgotten Crew Bears come out and run old SAC checklist very scary stuff!.

There should have been a battery checkout performed and possible battery R&Rs after the LCC went down.

You REALLY don’t want the DC brushes to drop down during MG startup (another great reason for the switch) as there would be 32VDC lightning and a lot of smoke as the MG goes into self destruct mode.

P.S. One day you will miss that old MG humm.



And I was permanently decertified on Wing 6 LF Motor Generator checkout by the DCM. Bah!
:wink: But that’s another story
Last edited by Pappy on Mon Jan 29, 2007 4:46 am, edited 2 times in total.
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Postby Pappy on Mon Jan 29, 2007 2:13 am

Oh one more thing sir,

If you (or any Montana capsule crew that read this) happen to be on the SIN line with an MMT Team Chief named TSgt Gabe Nelson ask him…

So, what cha wearin?
:) Something he always used to ask my wife on the phone

To add to his confusion you can say…
“Weee Ooo Weee Ooo Oh I can’t remember my line”
Which he should respond with …
“I think it’s Haakhh”
That’s from the movie Kung Pow! Enter the Fist
:lol: A must see while inebriated movie!

If you have issues with the above you can just ask him which he thinks is better a 600 Ninja or a Harley RKC.

Then you can tell him I put you up to it.
He is pretty smart for a knuckle dragger though he might figure out I put you up to it on his own.
:P
Ah just taunt him mercilessly for me.
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Re: Motor Generator Q

Postby MattX1 on Wed Sep 26, 2007 4:07 pm

Pappy has it correct as far as what happened in this situation. I was working in MMOC when this happened. I spent a long time on the phone trying to get an answer as to what position the DC switch was in.
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Re: Motor Generator Q

Postby LA CrewDawg on Fri Sep 28, 2007 5:59 am

Pappy,

Awesome MySpace!
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Re: Motor Generator Q

Postby Pappy on Fri Sep 28, 2007 12:13 pm

Thank you :D
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Re: Motor Generator Q

Postby LA CrewDawg on Fri Sep 28, 2007 9:38 pm

Pappy,

If you're ever on a ride around St Pete and run in to a retired MH53J Special Ops Helo pilot named Ray, tell him I said "Hi" He'll be easy to pick out in a crowd. He's 6'4".

Scott
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Re: Motor Generator Q

Postby SSgt Tom on Thu Nov 13, 2008 11:32 pm

I was at Minot 1971 - 1974.

As I recall, to start up or shut down a MG we had to first take the air vent screen off of the one end of the MG exposing the dc brushes and install some clear plastic flexible clamps to hold the brushes up. Hands-on training and skill needed first to be able to install the clamps properly. No switches.

For start-up, then plug in the ac in and output cables and turn on the ac breaker. Then plug in the DC cable and remove the plastic clamps, put screen back on.

For shutdown, then unplug the DC cable, then turn off the ac breaker.
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Re: Motor Generator Q

Postby Ducky on Fri Nov 14, 2008 6:12 am

No clamps like that anymore, just switches. You start up the MG on AC, with the brushes down. Once the MG hits its operating speed (not very long), you turn on the DC breaker picking up the brushes. At the LF its a big breaker style box mounted near the MG, at the capsule its a toggle switch on the MG under a small round door we pull up.
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