In this video, we will talk about if it is ok to use a disconnect between VFD and Motor? A quick answer
is Yes. It is ok to use a disconnect. But there are a few things to be considered for doing so.
Provide additional safety for the user in the event of any kind of maintenance on the motor or on the output of the VFD.
On top of that, other thing to be considered as well is, in most applications, this is very common thing to see.
And this also stop from any unintended operation even there is run command from the drive side to run the motor. This will ensure
That if any reason the motor shouldn't be running, that is one way to stop it from doing so.
Having said that, there are a few things that need to take in consideration. One thing is we do not recommend having
The disconnect closes while Drive already has power applied to the output sides with the commands enabled, will cause slamming effect.
Now, slamming is where
The output of the VFD rippable because it is assumed to run at that speed.
It will cause endure stressed on IGBT components.
will cause huge amount of current spike as well.
And of course doing so,
It will cause VFD fails prematurely. So you want to make sure disconnect is closed when running the VFD.
Now in some cases, it is been known that adding fast acting contact on disconnect
By a permissive functionality is a good idea. That will ensure the drive won't run unless the permissive and run command are made.
Which means the contact is already closed before the run command is active on the VFD.
So for that being said
An example the thing is mentioned
here regarding permissive,
Looking at ATV630 here using SoMove, a Freewheel stop assignment is a good idea to use for permissive. Go to Generic Functions,
Then go to Stop configuration, there will be Freewheel stop assignment here.
Can program an input to a logic that is needed here.
And again, what would happen is that unless that logic is active.
It will stop running the VFD even the run command is active.
Something has to be control on the disconnect between
drive and motor
Other thing is considered as well is that a lot of time, you may decide to choose a Freewheel stop. Because when you give a stop command,
to the VFD, what it does is that it will decelerate down to zero. It doesn't just go ahead
go from 100 to zero speed depended on deceleration time.
Deceleration time is in Simply Start menu, normally it is set for 10 seconds.
In the even that you don't want any control of the VFD during deceleration time,
What you can choose as well is go to Generic Functions, you can go under the
stop configuration again and you'll notice that type of stop is ramp stop,
and in event, you don't want any control the motor during stop mode,
you can select Freewheel stop.
which can help you not having any interfere to run the disconnect open or close when that command is active.
So just shed a little light on whether or not using a disconnect between a VFD and motor on Altivar Drives.