Welcome to the first edition of problem solved here at KEB America.
I'm here with Carlton stripe, an application engineer. I want you to tell
us what our topic is for the day. Today is DC injection braking. You're
gonna hear all about it in just a second. Let's do this.
I'm here with Carlton Stripe.
He's an application engineer and he's gonna tell us a little bit about DC
injection breaking. So Carlton, can you give us an overview of what it is.
Yeah, so DC braking is a method for
three-phase AC induction motors. It's a method to decelerate a load of high
inertia moving at high speed to decelerate it quickly and effectively
without friction components or letting the load coast to a stop. So out in the
field what would be some applications where you would implement this type of
braking? Yeah, so DC braking is best used for trying to decelerate a load
that has high inertia moving at high speeds as I mentioned. One example that
might come to mind is that of like a rotary grinding wheel. If an operator is
working on it grinding a piece of aluminum or metal and they want to stop,
not emergency stop, but just bring the motor and the load to a zero
speed position, you can use DC braking to decelerate that load, because that high
inertia, you know if the power was just removed
it could take a long period of time, may be multiple minutes to bring to a stop,
just based on coasting through friction. So would you be able to give me a
demonstration using the setup here of how DC injection braking works?
Of course, we can set it up and show you with and without DC braking. All right here
we have a little demo set up to demonstrate DC braking. We have an F5
drive that's programmed into an open loop configuration, and a small AC
three-phase induction motor here. In this drive I have programmed default parameters
for open loop control. And in open-loop drives from KEB we
have default parameters set up for DC braking capability. The only modification
I made for this example is I lowered the maximum voltage just slightly, just to
accommodate the smaller motor here for our example. So I'm gonna start up the
motor. And we can see the motor will start and spin at about 40 Hertz here.
And if I were to remove the AC power the motor would slowly coast to a stop.
Now, if we had a high inertial load like a big grinding wheel or something on here
that could take a considerable amount of time to coast to a stop through friction.
But now we will ramp the motor back up to speed, and we'll apply our DC braking
and we can watch how fast the DC braking stops the load. Almost immediately it
brings it to a nice halt. And then the DC braking by default parameters will run
for a programmed amount of time and then put the drive into LS. And then if the DC
braking input is removed, motor function will continue.
And so what would be some pros and cons to
using this in the field? So a definite pro is with DC braking you
don't need any additional components. There's no friction brake that's
required. Literally it's just using the drive and the motor itself, which you
already have. So there's no extra braking equipment that is needed. No wear
components that wear out. So essentially there's really no components that need
to be replaced or purchased in addition to the components you might already have
in your industrial automation application. You also, with high inertial
loads trying to decelerate them through the deceleration ramp of the drive,
pushes a lot of that regenerative energy back into the drive, and sometimes can
cause an over-voltage or an E.LP error. One limitation however of DC braking, is that
applying a direct current to the stator almost is as shorting, it almost acts as
a short-circuit to the coil, to the windings inside the motors. So you know
that's something that you want to be cautious of and not apply the DC braking
for very long. So DC braking should not be
used to hold a load, it should only be used to quickly decelerate a load and
then removed so as to not overheat the motor. I hope we learned something
Carlton here is a very smart guy and we're grateful to have him here at KEB
America. So that was our first episode of Problem Solved. We look forward to giving
you more insights into different automation applications.