Jeff Major <
[email protected]> wrote:
>
> Hi Robert,
>
> The classic meaning of plugging is to reverse the
> field of the motor while the motor is at speed. With
> a series wound motor, this results in about twice the
> stall current and twice the stall torque. Which is
> likely enough to tear apart the drive line or lock up
> the wheels. So, when solid state controllers are
> used, a normally reversed biased diode is placed
> across the armature, called the plugging diode. Then,
> when the field is reversed, the plugging diode
> conducts and you only get stall torque instead of
> twice. The controller further controls the plug
> braking by pulsing the field, to weaken the braking
> torque and lessen the current. The current comes from
> the battery. The braking energy is dissipated in the
> motor armature and plugging diode.
>
> Plug braking is a legitimate method of electric
> braking. Forklifts use this method with series
> motors. Forklift operators seldom use the brakes.
> They just go from forward to reverse. It is very hard
> on the motor, but forklift motors do survive. With
> modern separately excited systems, plug braking is
> also available. I use this on vehicles powered by
> generators, where regeneration is not possible. On
> the battery powered versions, I use regen systems.
> >From the driver's feel, he cannot tell the difference.
>
> Obviously, regeneration is the preferred method.
>
> Hope this helps.
>
> Jeff M
>
>
>
> --- Robert MacDowell <
[email protected]> wrote:
>
> > I see plug braking referred to in DC controllers,
> > but very little is
> > said about it. What is it?
> >
> > At first blush it sounds like dynamic braking, but
> > wait -- I'm a
> > railroad guy, so I'm familiar with dynamic braking
> > as per locomotives:
> > Reconfigure the traction motors as generators, then
> > waste the regen into
> > big racks of resistor grids. It's so effective that
> > in hill country,
> > they add locomotives to trains just to provide
> > dynamic brakes.
> >
> > But in the schematics I see for plug braking, I
> > don't see any resistor
> > grids. Where does the heat go?
> >
> > Robert
> >
>
>
>
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