MacFormat 1994 November/macformat-018.iso/Utility Spectacular/Utilities/EVDesign 1.1/MiscInfo/Motors.Txt

Text File | 1994-05-20 | 10.8 KB | 276 lines | [TEXT/MSWD]

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Miscellaneous motor info gleaned from the EV mailing list on the Internet
Thanks to all who contribute to that group!

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Date: Wed, 10 Nov 1993 09:44:00 BST
From:[e-mail]
To: Multiple recipients of list EV <[e-mail]>
Subject: Re: motors

        Yes there was some talk of a pancake motor, I have talked to the
designer and the motor is available for use now.
        The motor was designed by one Cedric Lynch and is a re-interpretation
of a printed circuit motor. It is currently availably in only one size
approx 8" dia. and about 4" thick weight is 24 lb but this may be lowered to
20 lb power output is approx 8kw continuous at 4000 rpm with 20Kw peak,
current built to order cost is 750 pounds sterling.
        Four of these motors were fitted to a hydroplane to take the
electric world water-speed record at 65 knots (driven by the Countess of Arran)
        The motor is used with a transmission, Cedric has an enclosed motorbike
(using mountain bike parts for light weight) which using car starter batteries
approx 36Ah (six off) travelled non-stop from London to Birmingham.
        If anyone wants more info, best phone me.

                582 760986  (home) 6pm - 11.30pm
                582 763133  (work, SLOW swithcboard, plus its a big site
                                I could be anyware!)

                Paul Compton
                        Rothamsted Experimental Station
                         Worlds oldest agricultural research station
                          150th Aniversary year.

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Date: Wed, 10 Nov 1993 10:10:43 U
From: Kevin Scoles <[e-mail]>
To: Multiple recipients of list EV <[e-mail]>
Subject: Re: motors

        Reply to:   RE>motors
There is a short mention and figure of such a motor (a flat one in the wheel
itself) in the IEEE Spectrum, Vol. 29, No. 11, November '92. The motor was in a
Tepco "Iza" concept car. Each of the permanent-magnet brushless dc motors
developed a max of 42.5 kg-m torque. The motors were rated at 25kW each, and
consumed 56 Wh/km at a constant speed of 40 km/h.

BTW, this issue of Spectrum has four articles on EV's,
    Electric Vehicles: why now?
    Pursuing efficiency
    Archtecting the system
    The great battery barrier.

Interesting reading

Kevin Scoles
Electrical & Computer Engineering
Drexel University
and SunDragon Race Team

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Date: Mon, 28 Feb 1994 20:17:33 -0800
From: Don Rodes <[e-mail]>
To: Multiple recipients of list EV <[e-mail]>
Subject: New GE Drive System

Amanda Mesler, EVS Automotive Market Manager for General Electric
DC Motors, announced plans to market GEUs new state of the art
shunt motor automotive control system with on-board diagnostics
through their Master Distributor for North America, Pro Electric
Vehicles (ProEVTM).

The system is an integrated package including a shunt wound motor
rated at 50 peak horsepower, fully enclosed IGBT based controller,
dash display meter, and an accelerator control box. Standard
features such as variable regenerative braking, input voltage
range of 72-144VDV, on-board diagnostics, battery state of charge
indication, and hour meter are incorporated into the system, which
has been in development for over 3 years.

The greatest advantage of the shunt wound system is the ability to
easily control the available 250 amps of regenerative current
capacity of the system. This allows a significant amount of energy
to flow back into the batteries as the vehicle is decelerating or
descending a hill. The additional feature of controlled field
weakening allows the motor to operate more efficiently and at
higher speeds under varying load conditions.

The system was developed, field proven, and is currently in use in
electric mini-vans, the first zero emissions vehicles (ZEV)
produced by a big three auto maker to be certified for sale in
California under the 1998 CARB mandates.

Pro Electric Vehicles (Pro EVTM) will be responsible for sales,
distribution, service, and technical training relating to both
GEUs new shunt motor system and their familiar industry work
horse, the EVT-15 series motor control system, which has similar
diagnostic and battery state of charge indication features.
Interested parties should contact Pro Electric Vehicles, 11852
Eddy Ranch Road., Penn Valley, CA 95946, Tel [phone], Fax
[phone].

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Date: Mon, 28 Feb 1994 12:05:30 PST
From: schaefer, chris <[e-mail]>
To: Multiple recipients of list EV <[e-mail]>
Subject: Re: Electic Motors

> Subject: Electic Motors
> Author:  Electric Vehicle Discussion List <[e-mail]>
> Date:    2/28/94  10:04 AM
>
> Good Day.....
>
> I've been doing some work on "Right Sizing" the motor and batteries and
> came up with some interesting numbers.
>
>
> Assume you have a motor and batteries which are "Right Sized" for pickup
truck.
>
> >From the book "Build Your Own Electic Vehicle", I got two equations for
> a series motor.
>
> (1)  T=K*I^2

While I enjoyed Bob's book much, I found that this equation just didn't add up
from an EMPIRICAL STANDPOINT on series wound motors.   Yes, the field strength
is dependant on I, and the torque should be I in the armature times the field
strength which is the I ^2.  However, if you look at the charts published by
Advanced D.C.  you will find a remarkably LINEAR ( ie I ) relationship between
torque and current.  It's as though these motors behave more like permanent
magnet motors than series wound.   I suspect that there is some magnetic
saturation taking place which limits the field strength such that at very LOW
currents you get an I^2 relationship, but that once you hit satuaration you get
a simple I relationship.  I plan on talking to Advanced D.C. at pheonix about
this issue because clear the theory and the practice don't seem to be adding
up.  Perhaps someone knows these numbers better than I......

If we approach motors from a black box perspective, you get a DIFFERENT
theorectical equation which is simply this.
Power in = Volts * Amps.
Power Out = Torque * RPM.
   so,
Torque * RPM  = (efficiency )  * Volts * Amps.

I prefer to use this when calculating since the laws of thermodynamics haven't
yet been violated. ( unless we're on to something with these motors :-) )

>
>   and
>
> (2)  S=(V-IR)/KI
>
>   where T is torque
>         I is current
>         V is terminal voltage
>         R is internal resistance of motor
>         S is Speed of motor (RPM)
>         K is a constant which is related to the motor characteristics
>           NOTE: the K in 1 & 2 may not be equal but are related.
>
> Assume T' = T/2 (my EV should weigh halve as much, so I should only need half
>                  the torque).
>        I' = I/2 (the 12 volt batteries have half the current available).
>        S,R,K,V held constant.
>
> (1') T/4 = K*(I/2)^2
>
>      T'/2 = K * I'^2  NOTE: halve the current and I quarter the torque.
>
> (2') 2S = (V -2(I/2)R)/K(I/2)
>
>      2S = (V -2I'R)/KI' NOTE: halve the current and I almost double the speed.
>                               the -2I'R should slow things down a bit.
>
> Now if we exchange speed for torque we can get T' @ S,I' but we have to use
> a reducer gear to do it.
>
> One conclusion that I get from this is that you may not want to use the same
> motor on a Truck as you would on a subcompact. The second conclusion
> (and the one I like the least) is that series dc motors need matched current
> and Voltage to work well, and that it works better at high current, so high
> voltage is needed as well.
>
> Have fun....
>
> Bob....

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Date: Wed, 30 Mar 1994 13:01:58 PST
From: schaefer, chris <[e-mail]>
To: Multiple recipients of list EV <[e-mail]>
Subject: Re: Electric Motors

Bob Wrote---->
> Good Day.....
>
> I've been doing some thinking on "Right Sizing" the motor and batteries and
> came up with some interesting ideas.
>
> Assume you have a motor and batteries which are "Right Sized" for pickup
truck.
>
> Assume you could split the battery pack in two equal battery packs and switch
> them between parallel and series configurations (a DTDP relay/switch or
> possibly three semiconductor devices (SCR? or MOSFET?) will do the job)
>
> (1)  T=K*I^2
>
>   and
>
> (2)  S=(V-IR)/KI
>

I believe that I recognize these two equations from Bob Brandt's book.
However.  I've come to believe that equation (1) is INCORRECT.  I know that if
you think about two fields operating against each other that I^2 seems right,
but if you actually LOOK at the curves published by, say, Advanced D.C.,
Torque is proportional to current much like a permanent magnet motor....  I may
be wrong, but perhaps the field is becoming saturated.....   Anybody have any
ideas?
-Chris-
#define  email   '[e-mail]'
#include <std.disclaimer>

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Date: Fri, 8 Apr 1994 11:28:20 -0600
From: Bob Jackson <[e-mail]>
To: Multiple recipients of list EV <[e-mail]>
Subject: Re: DC Motors

>Good Day.....

>I used the tabular data I found for the 9" Adv. DC motor to create the
>some (hopefully) interesting data.  I can't explain it, but maybe if
>someone has Adv. DC phone number I can ask them about it....
>
>results: T can be approximated by              kI^1.5
>                                  -----------------------------------
>                                  eff of the motor(parameters unknown)
>

I think I can explain it now......

T = K*Phi*I

for LOW current Phi is equal to K'I so T = KI^2
but as current increases the Air Gap Magnitisism cause
Phi(high I) < Phi(low I)  I will guess that
(hand waving on)
Phi = K'I^n where n = 0.5 +/- n' where n' is < 0.1 and may be a function of I

This explains why the eff term improved the results because it took into
account the air gap problems.
(hand waving off)

I'm going to rework my numbers over the weekend and maybe I'll have some thing
useful to share.  One thing really puzzles me is why is the air gap point so
low?  I wonder what the engineering trade offs were that would allow a air
gap point at about 100 amps (whine).

Have a good one...
Bob

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