Today's Message Index:
----------------------
1. 09:44 AM - Re: Re: AMPS? (FLYaDIVE)
2. 10:07 AM - Re: Re: AMPS? (GRAHAM SINGLETON)
3. 10:29 AM - Re: Re: AMPS? (FLYaDIVE)
4. 10:49 AM - Re: Re: AMPS? (FLYaDIVE)
5. 02:03 PM - Re: AMPS? (rparigoris)
Message 1
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>
> Ron:
>
You are going to have to explain your statement on this on:
" in reality when you lower the voltage going to an electric motor the amp
draw drops."
When you lower the voltage AND the motor still runs the AMPERAGE MUST GO UP.
I = E/R
The FIXED is the Resistance. The only variance in the Resistance is due to
Heat and Brush Ware.
At some point in dropping the voltage the motor will not function - That is
because the voltage is too low to produce an inductive field in the stator
and rotor..
BUT! As long as the voltage is enough to make the motor move the Current (
I ) will go UP.
There is NO OTHER - REALITY - Statement.
I know, I know I'm a PITA and a stickler to detail.
>
> "I also don't know for certain if toe 600 watt number is actual amp draw or
> the output of motor. If it is the output of the motor then you have to add
> in some amp draw because the motor is not 100% efficient."
>
There are two (2) things not known:
1 - When and How the readings were taken to determine the 0.6KW... As I
stated in my previous post. I betting they were taken AFTER the starter
motor reached full speed.
2 - You statement of "100% efficient" does not have ANYTHING to do with
this. Efficiency is equal to OUTPUT divided my INPUT. % - IN / OUT. And
we don't care what the OUT is. We are only interested in what the IN is...
HOW MUCH INPUT CURRENT will the Starter Motor draw during startup.
AND - It is the instantaneous Current with the high mechanical load that the
Wires must handle.
AHhhh clamp on meters... That is what I'm betting the the manufacture used
to get the current draw.
They show ONLY an RMS value and not the peak. Guess-factoring you can add
29.3% <<<--- a real number, more to that reading to be more in-line with
what the wire should be handling. And "should be handling'", my quote, does
not give a safety margin. A step up of at least one wire size would be
minimum.
Again I must state: I know, I know I'm a PITA and a stickler to detail.
Barry
Message 2
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No. The faster the motor runs the greater the back EMF. So the lower the
=0Acurrent.=0AGraham=0A=0A=0A=0A=0A________________________________=0AFrom:
FLYaDIVE <flyadive@gmail.com>=0ATo: rotaxengines-list@matronics.com=0ASent
: Sunday, 3 October, 2010 17:42:01=0ASubject: Re: RotaxEngines-List: Re: AM
PS?=0A=0A=0ARon:=0A>=0A=0AYou are going to have to explain your statement o
n this on:=0A" in reality when you lower the voltage going to an electric
motor the amp draw =0Adrops."=0A=0AWhen you lower the voltage AND the motor
still runs the AMPERAGE MUST GO UP.=0AI = E/R=0AThe FIXED is the Resista
nce. The only variance in the Resistance is due to Heat =0Aand Brush Ware.
=0AAt some point in dropping the voltage the motor will not function - Tha
t is =0Abecause the voltage is too low to produce an inductive field in the
stator =0Aand rotor.. =0ABUT! As long as the voltage is enough to make t
he motor move the Current ( I ) =0Awill go UP.
Message 3
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Hello Noel:
I really like your idea of a Ground Power Connector, they offer all sorts o
f
advantages.
How does being on floats negate the Ground Power Connector?
As you know and mentioned, wire run length is a major factor. An AWG of 2
should do well for short runs of wire and that #2 does have a safety margin
figured in. Going to an AWG of 0 for BOTH POSITIVE & NEGATIVE runs should
work VERY well.
I have never use it - But, there have been many reports of using 'welder's
cable', very flexible, abrasion resistance, low resistance and available at
welding supply houses. They also have the ring lugs.
AND - Gaggle - I know I posted this before but it REALLY is a GREAT TRICK:
SOLDER the wire to the ring lug ONLY at the end next to the mounting part o
f
the ring lug.
Crimp First - Then older. Clean well.
Barry
On Fri, Oct 1, 2010 at 7:40 PM, Noel Loveys <noelloveys@yahoo.ca> wrote:
> Barry:
>
>
> If I read you right you like myself feel the 6Ga. feed wire is a bit on t
he
> light side. I agree if someone was to try to push 100 A through that wir
e
> it wouldn=92t be long before it would heat up and cause even greater
> resistance.
>
>
> What would you think an acceptable gauge for the starter feed wire to be?
> 2Ga. ground straps were mentioned.
>
>
> I=92m almost ready to install the battery in my 912 mod. I think I=92ll
have
> to put the battery behind the seats and that means around an 8=92 run. I
=92m
> seriously considering 0Ga or 00Ga. wire. If I weren=92t on floats I=92d
install
> a ground power connector.
>
>
> Noel
>
>
> *From:* owner-rotaxengines-list-server@matronics.com [mailto:
> owner-rotaxengines-list-server@matronics.com] *On Behalf Of *FLYaDIVE
> *Sent:* October 1, 2010 7:28 PM
> *To:* rotaxengines-list@matronics.com
> *Subject:* Re: RotaxEngines-List: Re: AMPS?
>
>
> Ron & Dan:
>
>
> Here is the math for the information you gave:
>
> 0.6KW = 600 WATTS
>
> 600 WATTS @ 12 VDC (I use 12 V because you are pulling the power from the
> Battery)
>
> I (current) = 600 W / 12 VDC = 50 AMPS But at WHAT TEMP?
>
> Lets also use 8 VDC... Why? Because many starters will turn over at a mu
ch
> lower voltage than 12 VDC to insure starting when the battery is low and
the
> temp too. SOoooo...
>
> I = 600 WATTS / 8 VDC = 75 AMPS But again at WHAT TEMP?
>
>
> I have VERY STRONG reservations to where and how they came up with this
> 0.6KW.
>
> It sounds way - way too low.
>
> I'm betting that current (0.6KW) is a sustained current AFTER the initial
> surge.
>
> I doubt if they used a current probe connected to a digital O-Scope to
> capture the true current draw. Having done amperage checks on small
> lawnmowers, they were pulling 100 Amps on a SUMMER DAY.
>
> Don't go borderline.
>
>
> Barry
>
>
> On Fri, Oct 1, 2010 at 3:38 PM, rparigoris <rparigor@suffolk.lib.ny.us>
> wrote:
>
> rparigor@suffolk.lib.ny.us>
>
> Hi Dan B.
>
> The old style starter draws .6kW.
>
> According to Lockwood, the new style starter draws less amps.
>
> For a quick estimate using 60 amps for old style and 50 amps for new styl
e
> will get you very close to what is probably real draw. Remember this engi
ne
> is not too much over 70 cubic inches, not 200, 320, 360 or larger.
>
> This info I gathered was based on a 914, but would imagine the 912S would
> be very similar.
>
> You can choose a larger resolution and look at starter on the right side:
>
> http://www.europaowners.org/forums/gallery2.php?g2_itemId372&g2_imag
eViewsIndex=1
>
> Note if you run starter for 10 seconds, you should wait 2 minutes for coo
l
> down.
>
> I have a Odyssey PC525 mounted aft in fuse and am using #4 CCA. Others
> using #4 have good success, but #2 wire would be a little better.
>
> I think in your instance if #6 worked before, it will work better with th
e
> HD starter.
>
> The wire I am using is copper clad aluminium. The diameter is larger than
> #4 copper but the resistance is just about the same. I almost took the
> yellow covering off the wire and stripped out strands to make it #5 to sa
ve
> a little weight, then heat shrink Teflon heat shrink over the strands.
> Sounded good, would have saved a little weight, then I realized just how
> much weight it was going to save from my rear pocket and idea was put in
the
> bin.
>
>
> Ron Parigoris
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=314349#314349
>
>
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> --
>
> Barry
>
> "Chop'd Liver"
>
>
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>
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Barry
"Chop'd Liver"
Message 4
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Gaggle:
> WHAT A SCREW UP!
>
I put in the wrong formula.
I = P / E
Sorry - Did anyone else catch it?
Barry
>
> Ron:
>>
>
> You are going to have to explain your statement on this on:
> " in reality when you lower the voltage going to an electric motor the amp
> draw drops."
>
> When you lower the voltage AND the motor still runs the AMPERAGE MUST GO
> UP.
> I = E/R
> The FIXED is the Resistance. The only variance in the Resistance is due to
> Heat and Brush Ware.
> At some point in dropping the voltage the motor will not function - That
> is because the voltage is too low to produce an inductive field in
> the stator and rotor..
> BUT! As long as the voltage is enough to make the motor move the Current
> ( I ) will go UP.
>
> *
>
> *
>
>
--
Barry
"Chop'd Liver"
Message 5
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Hi Barry
"It's true that to achieve the same watt output with a lower voltage you need to
up the amperage, in reality when you lower the voltage going to an electric
motor the amp draw drops."
If you have a battery or power supply with wires that can keep the lowering of
voltage and amperage to a minimum, then it's true that if you lower the voltage
to a motor that is reasonably loaded the amp draw will go up since the motor
can't spin as fast as if it had higher voltage (within reason as far as voltage
and load and motor timing).
What I was getting at is that often (VERY OFTEN with high performance moder electrics)
you may have a battery and wire size that is very close to asking max.
amps that the battery can offer while maintaining a reasonable voltage.
If you ask any more amps it will begin to give up a lot of voltage and not offer
up any more amps. If you have long thin wires that only drop voltage further,
then heat the wires up and drop voltage even further, often you are asking more
amps from the battery that it can put out. The scenario is the battery is
huffing and puffing harder and harder but begins dropping amp output and voltage,
and the wires are warming up and making things worst. Net is if you see too
little voltage at a running loaded motor (again within reason and you calculated
what you are looking for), it probably means you have a battery that has
not enough ability to dump amps and keep the voltage up, and or the wires are
creating too much resistance and dropping voltage. In this scenario of marginal
battery and wires, lets put it in the cold where the battery is offering up
even less performance and the motor is offering up more resistance to turning
and we measure a lower voltage going to the motor, the motor will just plain not
be seeing very many amps going to it compared to a warm battery and engine.
Again what really matters to me is when it's cold out I can start my bird.
BTW on cars it works where on a cold day if you turn on all loads for a few minutes
before starting the the warming up of the battery compared to the watts used
nets to more cranking power.
Also with electric motors timing is every bit as important as on IC motors. You
want to select proper advance for what you are doing. You never want to run a
brushed motor retarded from neutral. Amp draw will go way up and brush life and
power output way down. Select too much advance for a highly loaded motor and
if you can provide enough amps you will get a little more power output, but
often the battery/wires net to less power and you are better off running closer
to a neutral timing. I wouldn't be too surprised if someone tried a few motors
and optimized timing for our 91Xs to get the high output version that draws
less amps than the original. I wouldn't be too surprised if the original motor
wouldn't benefit a lot by optimized timing, but then again it may not be too
easy to adjust.
Ron Parigoris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=314525#314525
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