Re: surging, motor

[Michael Neverdosky <MichaelN cycat com>]

You can set up any DC motor for dymanic braking but for something 
like the snowblower you want to be carefull and not make the braking
to strong as you might damage the equipment by twisting shafts,
shearing bolts etc.

You can reduce the amount of braking by using a resistor in series 
with the armature instead of a direct short. This limits both the
motor current and the braking force (torque).

You will need to experiment with the size of resistor to get it to
stop as quickly as you want but not to quickly. I would start with about
2 or 3 Ohms and add resistors in parallel (reducing the resistance) until
it would stop the way I wanted.

I have used this system on RC electric powered airplanes many times and
it works well. The motors with direct drive and light props were fine
without a resistor, but the ones with a gearbox and large prop needed
between 0.25 and 1 Ohm to prevent damage to the motor, prop and/or
stop switch.

You could wire up an "EMERGENCY STOP" switch that is just for emergencies
where you have a big red button that would switch relays to cut power
to the blower and short the motor for the fastest possible stop in case of
emergency only.

michael

kdo cosmos5 phy tufts edu wrote:
> 
>    From: "Naugler, Steve" <SNaugler Rodel com>
>    Date: Mon, 4 Jan 1999 13:42:30 -0500
> 
>            The traction motor, snow blower motor, and most other of the 
> GE
>    accessory motors, when turned off coast slowwly to a stop.  In these 
> cases
>    the armature connections are left floating when turned off.  This is 
> a case
>    of (hopefully) low friction braking.  I am very careful when 
> snowblowing
>    because the blower takes forever to stop and I worry about kids and 
> pets.
> 
> Could one modify the snowblower motor to have braking when turned off?
> That would make it a lot safer.
> 
>                                 Ken