Question: does anyone know if the occasional reversing of an electric decreases its life, or possibly even extends it?
To: electricboats@yahoogroups.com
From: pembertonkevin@gmail.com
Date: Fri, 15 Jul 2011 12:54:38 -0600
Subject: Re: [Electric Boats] Re: DC Brush 'Timing'
Brushed DC motors do have timing. However most of what I know says the reason is to limit sparks in the commutator to brush gap. Typically motors designed to run in one direction the timing is off, but most motors designed to run either direction the timing is neutral for both directions.
I would guess on a brushless motor, this timing would be set to keep a negative magnetic pull after the armature passes set point. Also variable magnetic strength will keep the motor from loping from one pole to the next. Both brush and brushless gain using on current duty cycle. This type system must have a closed loop control circuit to work properly, and I don't know how many controllers have that option. A closed loop system would add complexity with a reliability cost that may not be worth the savings in energy.
On 07/15/2011 06:20 AM, John Green wrote:
To: electricboats@yahoogroups.com
From: pembertonkevin@gmail.com
Date: Fri, 15 Jul 2011 12:54:38 -0600
Subject: Re: [Electric Boats] Re: DC Brush 'Timing'
Brushed DC motors do have timing. However most of what I know says the reason is to limit sparks in the commutator to brush gap. Typically motors designed to run in one direction the timing is off, but most motors designed to run either direction the timing is neutral for both directions.
I would guess on a brushless motor, this timing would be set to keep a negative magnetic pull after the armature passes set point. Also variable magnetic strength will keep the motor from loping from one pole to the next. Both brush and brushless gain using on current duty cycle. This type system must have a closed loop control circuit to work properly, and I don't know how many controllers have that option. A closed loop system would add complexity with a reliability cost that may not be worth the savings in energy.
On 07/15/2011 06:20 AM, John Green wrote:
Thanks Eric,
Interesting. Possibly too complicated for my own particular intentions
regarding cost and minimal requirements/underbuilding but certainly
something for later, after I have learned to walk.
What might be interesting is to see if the amps to power ratio can be
changed this way, I suspect it would, probably not enough to matter, but
if so it would represent an efficiency gain, thus a range increase. I
was thinking more of an adjustable setup. Might be easy to do on some
motors, just by slotting out holes. I will look it up on EV sites,
thanks.
1b. Re: DC Brush 'Timing'
Posted by: "Eric" ewdysar@yahoo.com ewdysar
Date: Thu Jul 14, 2011 8:55 am ((PDT))
Hi John
Yep, you can do that. Any gains in one direction are offset by losses in
the other direction, i.e. reverse or regen. But some may feel that the
tradeoff would be worth it. The EV guys, who have much higher torque
and power requirements than we do, do this quite often.
Eric
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