# GE 11" max voltage?



## kerrymann (Feb 17, 2011)

I did some searching but the search function doesn't like search terms with less then 3 characters. This makes *GE *and *11 *hard to search for.  

Anyway I have a nice GE 11 motor that came out of an old conversion. It was run at a max of 120V and 600amps but i'd like to run at little more in my E30. 

Visually it looks identical to a Warp11 (nor surprise) and I am attaching the name plate.


I was assuming that it is neutrally timed but the brushes are angled so it was designed to run CCW. Were the GE's advanced? Advancing the brush holder is easy enough but I am open to recommendations on to what degree. Also does anyone know if GE 11 and Warp 11" use the same brushes? I would love to put some helwig splits and push it to 200V.


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## Duncan (Dec 8, 2008)

Hi Kerryman

Why are you worried about voltage?
In my understanding you can't overvolt a DC motor (within reason) using a current controlled controller (like most of them) 

It takes a low voltage (15v??) to get to 1000amps when stationary, then the back EMF kicks in

So the max voltage (at 1000amps) = 15v + back EMF - which is proportional to speed

A motor like the 11 inch GM will probably be OK at 4000rpm and questionable at 5000rpm

(At least that is what I was told about my 11 inch Hitachi)

So the problem is not being able to increase the voltage - that is set by the controller but how many revs can it do

I advanced my Hitachi by 8 degrees - seems to be OK

I am more than a little skeptical about the advantages of the spit brushes - I could see a wee bit better - but not the sort of advantages some people are talking

And I don't see at all how you would get a voltage advantage - they are not going to stop your motor from blowing up due to centrifugal force - and if no rpm increase - no voltage increase


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## Tesseract (Sep 27, 2008)

kerrymann said:


> I was assuming that it is neutrally timed but the brushes are angled so it was designed to run CCW. Were the GE's advanced? Advancing the brush holder is easy enough but I am open to recommendations on to what degree. Also does anyone know if GE 11 and Warp 11" use the same brushes? I would love to put some helwig splits and push it to 200V.


The brushes are angled to increase the contact area with the commutator and not to set a preferential direction. Brush advance does make operation in the opposite direction much less preferable, but you just limit current and RPM in that direction and you'll be fine.

I can't help you much with the rest of your questions except to say that brush advance is usually determined empirically by watching for the onset of sparking at the trailing edge as RPM is increased while holding current constant. Needless to say, this is easier to do on a dyno than in a moving vehicle (safer, too... ).

As for changing the brushes to boost the maximum voltage, I wouldn't count on that getting you more than 5-10V of additional margin because the maximum voltage the commutator can tolerate is primarily determined by the number of segments between any two brushes, with 15V per segment being a typical upper limit. And the voltage between commutator segments is proportional to both the RPM (voltage) and torque (current), with the latter also causing the neutral point to shift, which is where the inter-segment voltage is lowest and therefore the ideal place for the brushes to contact the commutator. This is the whole point behind advancing the brush timing - to move the brushes to where we expect the neutral point to be at overload conditions, thereby allowing the motor to tolerate overloads better.




Duncan said:


> In my understanding you can't overvolt a DC motor (within reason) using a current controlled controller (like most of them) ...


See last paragraph above. I know you said "within reason" but given the recent comments on AC motors are I felt it was important to point out that commutation failure is most definitely possible with controllers that regulate current, if that current is 4x or more what the motor is rated to handle "nominally", and especially at 2x or more the voltage. There is a time component to how much overloading can be tolerated as well (energy is proportional to I²t), but that is getting into more detail than I feel like typing at the moment...


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## kerrymann (Feb 17, 2011)

Duncan said:


> Hi Kerryman
> 
> Why are you worried about voltage?
> In my understanding you can't overvolt a DC motor (within reason) using a current controlled controller (like most of them)
> ...


Thanks. Correct on all counts. If I could run 400V on the motor it wouldn't help because I would run out of RPM before it was an issue (unless I had shiva with a kazillion amps). My experience has all been with 9" motors (GE, ADC, and Warp) so the 11 is new to me but I am unfortunately aware what happens when you go way over redline. But I would be very surprised if a neutrally timed motor can go to redline at 1000amps. For a neutrally timed motor I have thought the limit was 100-120V which I am assuming is too low to over come the back emf at 5000rpm. I don't have any dyno data for the GE 11" to say one way or another, hence my soliciting feed back.

As for the split brushes I also have reservations. I remember looking into it on my ADC 9", and talking with helwig about getting some. In the end I decided against upgrading because the brushes that I had in the motor were new, and I was doubtful I would get a meaningful increase. But there were people running the higher voltages with the helwigs. Could they have done the same with solid brushes? Maybe. But the method of finding out isn't easy (blowing up the motor). I figure if I am going to replace the brushes I might as well to do it with good ones. I am hoping to get some input from people who have been pushing the 11" in racing.


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## kerrymann (Feb 17, 2011)

Tesseract said:


> The brushes are angled to increase the contact area with the commutator and not to set a preferential direction. Brush advance does make operation in the opposite direction much less preferable, but you just limit current and RPM in that direction and you'll be fine.
> 
> I can't help you much with the rest of your questions except to say that brush advance is usually determined empirically by watching for the onset of sparking at the trailing edge as RPM is increased while holding current constant. Needless to say, this is easier to do on a dyno than in a moving vehicle (safer, too... ).
> 
> As for changing the brushes to boost the maximum voltage, I wouldn't count on that getting you more than 5-10V of additional margin because the maximum voltage the commutator can tolerate is primarily determined by the number of segments between any two brushes, with 15V per segment being a typical upper limit. And the voltage between commutator segments is proportional to both the RPM (voltage) and torque (current), with the latter also causing the neutral point to shift, which is where the inter-segment voltage is lowest and therefore the ideal place for the brushes to contact the commutator. This is the whole point behind advancing the brush timing - to move the brushes to where we expect the neutral point to be at overload conditions, thereby allowing the motor to tolerate overloads better.


Interesting. I had always thought the angle brushes did indicate direction. Increased area makes sense but wouldn't it be just as easy to make a wider brush? If seems like you have to make the brush longer to have it angled and end up with about the same brush material either way. 

I thought the angle was mainly to decrease drag and brush wear. I have noticed on a few motors that when I turned it the *incorrect* way there was more drag presumably because of leading edge of the brush catching in the gaps between segments. 

Funny enough on my trike I could watch the comm and brushes while riding. It was dangerously mesmerizing. Even more distracting then texting! 

Unfortunately some of us don't have our own motor dyno so I was hoping get some feedback from people with a ge 11 inch on the drag strip (either blown up or not blown up). 

Thanks,


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## kerrymann (Feb 17, 2011)

I was thinking of how I could check and see if the motor is neutrally timed or advanced. On the warp motors it is really easy because it is marked but I haven't seen anything similar on the GE. Best I could think of is looking at the location of the brushes relative to the field windings.

Thanks,


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## major (Apr 4, 2008)

kerrymann said:


> I was thinking of how I could check and see if the motor is neutrally timed or advanced. On the warp motors it is really easy because it is marked but I haven't seen anything similar on the GE. Best I could think of is looking at the location of the brushes relative to the field windings.
> 
> Thanks,


Hi kmann,

Aligning the brush contact centerline with the field pole centerline works pretty well for most of the motors we encounter like the Warps and most old fork motors because they have armatures wound with a 45º coil throw (symmetrical frog legs). But there are tolerance build-ups and actually other coil designs which are asymmetrical that won't conform to the pole bolt thumb rule. If you want to make a project out of trying to pinpoint the actual neutral position, try kick neutral. Here is a link which I found of a presentation describing methods to tune large DC machines. Kick neutral starts on slide #55. Note that it says not to attempt to use method on series wound machines. I'm not sure why because the field isn't energized during the procedure so what difference does it make if it is series or shunt? I used to do it with series motors. Just keep the armature voltage low.

http://www.wmea.net/Technical Papers/NECP--Tuning DC Motors and Generators.pdf

Also note that brush seating and rocking (positioning due to clearance within the holder from CW to CCW rotation) will affect your results.


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## kerrymann (Feb 17, 2011)

Thanks major. That is exactly the info I was looking for. It is advanced. 

I also took a closer look at the nameplate and I think it says it is rated @ 126.1V? In the box next to the amps box it says 126.1. The first 1 is covers the label but it looks like it was a V. The voltage range makes sense but such a specific voltage would be odd.


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## major (Apr 4, 2008)

I read it as 126.1V and 250A. That'd be about right for 37hp blower ventilated (BV) 1 hour rated, class H.


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## kerrymann (Feb 17, 2011)

major said:


> I read it as 126.1V and 250A. That'd be about right for 37hp blower ventilated (BV) 1 hour rated, class H.


Thanks. It's what I thought but I am curious how those GE engineers came up with such a specific voltage rating? Even down to a single volt seems overkill but rating these motors down to a tenth of a volt seems a bit ridiculous. Anyway with the nameplate voltage and the advance I am sure I could run 144v at 1000a. 160v should be okay but past that I am uncomfortable and is probably unnecessary given a 5k redline.


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## kennybobby (Aug 10, 2012)

*Nameplate*

So the engineers designed the winding to a 0.1 volt resolution?--lol. 

That is most likely the value measured during dyno testing--the 126.1 V was needed to make the motor spin at the nameplate speed when loaded with a torque such that the current was 250 amps. 

My guess is that the motor was tested in 25 or 50 amp increments as determined by the dyno torque load--all the parameters are recorded at each set point, then the data can be plotted, e.g. torque-speed graph. 

Looks like an awesome motor if it can run at 87% efficiency for 1 hour and not overheat.


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## kerrymann (Feb 17, 2011)

*Re: Nameplate*



kennybobby said:


> So the engineers designed the winding to a 0.1 volt resolution?--lol.
> 
> That is most likely the value measured during dyno testing--the 126.1 V was needed to make the motor spin at the nameplate speed when loaded with a torque such that the current was 250 amps.
> 
> ...


Well I think still think recording the voltage 4 significant figures on the nameplate is odd especially given that it didn't fit in the space on the plate and that the power rating is only 2 sig figs.

I understand what you are saying about it being the dyno but if that is correct I am surprised it takes 126.1V for only 250A and 2039rpm. I am not saying that is not the case but a Warp11 would only need 72V at the same point. So this one is wound for even more torque? 

If all the plate numbers are from a dyno run then:

-That 37hp nets 95ftlbs @ 250amps
-IF I could run 1000 amps that is 380ftlbs 
-That is assuming I could get to 1000a at a reasonable rpm and voltage

On the efficiency @ 1hour, That is the nice thing about the blower motors is you can have as much cooling air as the motor wants. And there is no internal fan robbing power or blocking additional forced cooling.


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