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

Re: (ET) Alltrax install!

Quoting David Roden <etpost drmm net>:


On 23 Feb 2006 at 8:05, john briese wrote:


It measure current and voltage and "knows" what is going on by
those measurements, not some crude poorly working temperature relay.


Are you sure?  The controller would have to keep track of time, too, and
guess at the accumulation of heat in the motor.  I don't know of any such
logic included, but I didn't design the controller, so it might be.
It may be crude but it works. You don't really need a thermal model, just some sort of current vs time profile. The average current matches motor temperature 
pretty well.  What that won't help you catch is unusually high temperature
operating environments or blocked cooling vents.
I've used that method myself and it did work. There are a lot of EVs ( a lot of 
forklifts) that run w/o temperature sensors.  My impression from a few
conversations with service personnel is that they (temperature sensors) are
seen as trouble prone, they would be a direct measurement though.  More 
useful
are brushwear indicators.


Robert Adsett <subscriptions aeolusdevelopment com> wrote :


I would call that regen not plugging.


Now there I'd have to disagree, though it's really a matter of 
nomenclature.
The controller and motor aren't returning any energy to the battery, so by
definition it's not regenerating anything.  It's >dissipating< the energy 
as
heat in the motor and controller.


It's mostly nomenclature, I wouldn't object to calling it something other 
than
regen but I do object to it being called plugging. The ONLY difference between shorting the motor to stop it and regen as far as the controller is concerned is the duty cycle of the short. If you open that short before the current drops to 
zero then you will feed current back to the battery.  To call braking with 
a
99% duty cycle short regen and that with a 100% duty cycle short something else 
seems odd to me but then I'm approaching it from the controller's 
viewpoint.

GE,Sevcon, Curtis, SRE Controls (Navitas) all use plugging to indicate a
specific kind electrical braking and regen to indicate another, shorting 
the
motor is just regen braking taken to the logical limit.

BTW, if Alltrax has a current limit during this braking then they will be
regenning into the battery unless they've added a braking resistor, it 
cannot
be avoided without adding a blocking diode.
Anyway, if they are using the term differently, then that's what they are doing. When I see plugging I see motor reversal and that's what struck me as strange. I've never seen the term used to mean shorting the motor. 

Robert