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.

8 thoughts on “What is DC Injection Braking? – Problem Solved”

  1. thats mean if i wanted to make this type of breaking to stop a motor i should make it in a pulses of d.c and not continuous

  2. No need to mess with custom controls, just install a plug and play braking system like this one: https://www.makesafetools.com/

  3. Nice video guys! I have a question about DC injection braking. Does a typical DC injection brake care about the frequency of its AC input or just the voltage? E.g. do they care about 50Hz or 60Hz as long as the voltage is as expected? I believe it shouldn't matter because the AC voltage is going to be rectified to DC but thought I'd ask some experts! 🙂

  4. this information about coil heating was very helpful thanks , what can we do to reduce the heating while breaking the wheel to stop ?

  5. I have problems with my motor, the brakes engage without a command. It does not run for more than 5 minutes. What could be the problem

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