Ganutenator
WOW
I have seen you post a lot of bad or misinformation and just let it go with no reply because most people can see for themselves and understand and there is no point in staring the pot but when you point the misinformation directly to me I feel need to post a response
As a reference I was doing drives before most on this site were even born. From pure DC systems Vacuum tube rectified DC motor controls, SCR’s drive systems AC VFD’s to the current VFD used today and I am still learning. I have machine manufactures using my control designs after I redesigned there controls for my clients. Factory service for multiple drive manufactures
I try to provide information to help others solve a problem they can use it or not it’s of no matter to me
And I have seen quite a bit of bad information posted here as well as a lot of good information it up each to take away what they want. Everybody has something to contribute
I like to think everybody that views or post here wants to learn or help somebody else
Posting that something is 100% false to me is on the verge of slander particularly when there is documented proof otherwise. It’s clear to me that you just don’t understand as much as you think you do.
It’s a well established and documented fact that DC Injection is limited to 30% of the motor rated torque. Starting at rated speed and falls off as the motor speed falls off. At zero speed you have zero toque. So holding a load at zero speed as needed for positioning is not possible
Take a minute and do the calculations, zero speed = zero torque no matter how much current / power you apply to the motor , Zero Torque means no power to hold the load. These are facts that don’t change. Try to suspend a load on a hoist at zero speed using DC Injection breaking. Make sure you stand well clear because I guarantee you will drop the load. I have suspended a load on a hoist motor many times using just a Flux Vector VFD and motor, and even them the motor shaft will obsolete for/rev while the load is held in position. But the motor shaft will be moving. The motor feedback tells the vfd where the motor shaft is and it calculates what’s needed to bring it back.
When stopping any motor you need to get rid of the energy in the motor
There are only a few ways to that
Mechanical Break Converting the motor energy to heat through friction in the brake
Dynamic Breaking Converting the motor energy to heat by passing the motor current / torque to a resister through the buss loader transistor in the VFD or using an external breaking module and resister
A quick Note here I like to use the term Buss Loader Breaking over Dynamic Breaking when talking about VFD’s While the way they work is different the end result is the same. Dynamic Breaking is an old term from the pure DC motors.
Common Buss configuration Multiple VFD’s shearing a common DC Buss So as one VFD is absorbing energy from its motor that energy is used by other vfd- motors sharing the common buss
Then there is Line Regeneration the motor energy is passed back into the AC Supply line where it can be used by other motors.
Then you have DC Injection breaking Injecting a DC current into 1 or 2 of the motor windings
Each method has their own advantages and disadvantages the system designer has to weight out all these and chose what’s best for their application sometimes they get it wrong.
Over the years I have designed and installed each of these systems without any problems.
As for you statement “ injecting DC into an AC motor will lock it up “ is false it will rapidly reduce the motor speed to near zero speed, within the limits described above it will not completely stop the motor ( friction on the motor will complete the final stop just like coast to stop) and if the DC is left on it will overheat the motor and burn up the windings that why the VFD limits the time and current for DC Injection Braking . Also some vfd’s allow you to use the DC Injection as a motor winding heater to keep the moisture out of the windings, again within limits
I noticed that you don’t like Yaskawa drives to each their own, But at least be honest about it.
You said NO RJ45 connector, everything in the last 20 or so years has one ( Keypad Port) I use it all the time in fact they also have a built in RS485 multidrop networking connection
So it would appear you are condemning something without having knowledge
They are the largest manufacture of drives in the world. Their drive technology is about 5 years ahead of the others. Tech support is next to none. There are many other reasons I recommend them.
I prefer not to use Rockwell if I have a choice. I have my reasons and will not discuss them here.
As for this application either they have a heavy friction load sopping the motor or they are using DC injection breaking you have ruled out everything else
I would still try the breaking resister I think it will give a consistent repeatable ramp
I have had conversations with tech support and the tell me the breaking is about the biggest support call they get because people don’t understand how it works and how to set it up.
If you want to continue this PM me