[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: (ET) corded mower motor



I knew there would be someone out there with the exact info!

>>> Rhett George <rtg ee duke edu> 5/13/2005 12:50:51 PM >>>
 - Greetings -

Bob Murcek asked about permag motors in corded lawn mowers.  Methinks
there
are two reasons for using the permag motor with its bridge rectifier.

  First - apparently lower cost in that the magnets are cheaper to mold
and
        magnetize  than the cost of winding a field electromagnetic. 
The 
        1989 Ford (Mazda) Probe I used a permag starter motor.  This is
a 
        high torque application.

  Second - in coasting, back EMF is generated.  By shorting this out,
i.e.,
        shorting the motor when the switch is open, a large torque in
the 
        direction of slowing the motor is developed.  This is simpler
than 
        using a friction brake with some linkage to apply it when the
blade
        should stop.

With regard to the induction motor, the torque vs speed curve is not
favor-
able when starting with the blade in tall grass.  It does not have
overload
characteristics that yield performance most users want in a mower.

Hope this helps.

                                        Rhett

_______________________________________________
Elec-trak mailing list
Elec-trak cosmos phy tufts edu 
https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak


IMPORTANT WARNING: The information in this message (and the documents 
attached to it, if any) is confidential and may be legally privileged. It 
is intended solely for the addressee. Access to this message by anyone 
else is unauthorized. If you are not the intended recipient, any 
disclosure, copying, distribution or any action taken, or omitted to be 
taken, in reliance on it is prohibited and may be unlawful. If you have 
received this message in error, please delete all electronic copies of 
this message (and the documents attached to it, if any), destroy any hard 
copies you may have created and notify me immediately by replying to this 
email. Thank you.