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| Ev Archive for July 1998 |
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| 1169 messages, last added Wed Aug 08 18:42:41 2001 |
[Date Index][Thread Index]
Re: motor problems/opportunitie
>Peter wants to add some other things, such as a permanent magnet
>field. Shari warns about making too many changes in a comfortable
>environment, but Peter thinks that the additional efficiency and
>the possibility of regen will outweigh the slightly lower torque.
>Eric
I personally wouldn't go for a permanent magnet field. If you have a
strong enough magnetic field for good torque, then the generated back EMF will
limit rpm, and hence power. There is no practical way to field weaken a brush
PM motor. There is in a brushless DC motor by careful manipulation of the
stator coils. It takes expensive magnets to resist de-magnetisation, and the
most expensive Neodimuim Iron Boron rusts like mad unless coated (the Lynch
motor uses galvanised magnets). The low inductance of a PM motor (there is less
iron near to the armature coils) makes implementation of the boost circuit for
regen harder.
I know the Lynch works well, but it's not big enough for the typical
car (it also has a 4000 max rpm rating).
I'd vote for a sep-ex motor. I make a distinction over shunt motors, a
sep-ex motor has a field capable of generating a flux equal to that of a series
field (at full rated voltage). Regen can be achieved mainly through field
control. Interpoles are highly desirable for improved commutation.
paul.compton@bbsrc.ac.uk paulceps@aol.com
Technical officer for the ECA
Tel No. +44 (0)1582 573195 home
(0)1582 763133 ext 2413 work
Join the UK Electric Car Association! 28 pounds per annum
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ECA website http://users.abling.co.uk/eca/
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