This project landed on my desk yesterday & I haven't done one of these before so I have a couple of questions.
I have 8 GV3000 drives controlling individual motors on a tube mill. They all run at different speeds that gradually increase from #1 to #8 in order to draw the tube down to the proper diameter. The rolls on each motor stand are changed frequently (at least 5 times per week) as the tube size requirements change or as the rolls get worn and have to be replaced. There's no PLC controlling this tube mill - it's all relays. They tried teaching the operators to change the parameters, but that didn't work too well so the electricians have to change the parameters. And no one ever bothered to hook up the manual speed pots either.
So... about 5 years ago, someone bought a Reliance Master Controller, but it was never engineered or installed for many & various reasons. Now management wants it installed this week because the mill is down for other upgrades.
The book says nothing using this with the GV series drives. I'm hoping that's simply because the Master Controller is older than the GV series. It looks to be a big pot that controls the incoming 115VAC to the transformer that steps down & converts the signal to 0-12VDC that is equally distributed to all the drives. Then that signal gets hooked to another pot at each drive to be able to tweak the final setting.
Is anyone else using a master controller? Is there anything else I need to consider before hooking this up?
Thanks in advance!
The link above will direct you to the web page that will get you the drive manual if you don't already have it.
A word to the wise. You should respectfully ask your Bosses for more time to make a well advised decision on the best method to control these drives. You may find that there are much better ways to do what you want to without spending a fortune. Get some advice from experts without being under the gun to implement a solution immediately.
Thanks, I already have manuals for both the drive & the controller.
> A word to the wise. You should respectfully ask your Bosses for more time to make a well advised decision on the best method to control these drives. You may find that there are much better ways to do what you want to without spending a fortune. Get some advice from experts without being under the gun to implement a solution immediately. <
I'm definitely doing that right now. I figure a week of engineering after 5+ years of the MC sitting in a box will be time well spent.
My problem is lack of "experts" which is why I'm asking questions here. I'm the only EE in the plant. The Process Engineer is certain that installing this won't work, but he's not happy with the current setup either. The Assistant Plant Manager is the one who's eager to do this because he thinks it will solve everything. No one has an open mind on the issue, so I have to have a clear, concise and convincing argument for my final solution.
The current setup has the 8 drives in series. There are no encoders to feedback the motor speed. The 1st drive's speed is controlled by a pot and then sends an analog output to the 2nd drive. The 2nd drive uses a gain parameter of about 1.05 to set its' speed and passes that to the 3rd drive, etc. The problem with this is that the gain can't be permanently set because no 2 tubes use the same ratios between rolls. Add that the roll diameter changes by 1/2" over the life of the rolls and this means that the operator or an electrician has to play with the gain to get the speed right. An operator has to have special training to run this mill since this is the only one setup in this way. The rest have only have 1 motor & a back shaft that turns the 8 rolls.
I'd personally love to put an encoder with a 1 ft wheel on each sizing roll, but there's too much fluid spraying in the sizing section. The encoder would either slip or gum up. Either one would not be good for the process.
So my idea using the MC is to set the fastest roll using the master pot and then trim all the other speeds down with individual pots. No more playing with gain parameters. All the operator has to do is turn a knob. This will have the advantage of being able to change 1 roll set without having to change the parameters on all the downstream rolls.
Personally, I wouldn't even bother with the MC except for the fact that it's already here and management wants it installed. I still have to buy 8 more pots and spend time for an electrician to install it... Time that I don't have with the current large project that's being installed.
I'd like to hear any & all suggestions. Just writing this helps me clarify it, but I'd like someone other than myself to look at it.
We have a tissue line with 4 GV3000 drives in closed loop vector, and have got some MKS BY150 synchronisers, all using the motor encoders and trim the speed references in the drive accordingly. This gets away from using encoder wheels.
Maybe a better option for you is to have the adjustment pots do trimming in their respective drives via the second analogue input. This way you would be able to limit the amount of trim the operator can do and provide a finer control to the movement of the pot.
I would like to do this, but there's only 1 analog input on this model.
> Maybe a better option for you is to have the adjustment pots do trimming in their respective drives via the second analogue input. This way you would be able to limit the amount of trim the operator can do and provide a finer control to the movement of the pot. <
I also went to MKS and looked at the BY150 that you referred to. If I had fixed diameter sizing rolls or if the entire set was all machined at the same time, this might work. But then so would have passing the analog output to the next analog input and multiplying by the gain.
It sounds like you want to control the synchronicity of the rollers. As the rolls wear then you must change the speed of the rollers.
#1. Make the system auto adjustable by figuring out a way to put an encoder directly onto the rolls (like you mentioned). This will give a true measurement of surface ft/speed.
#2. Use this measuremnt with a PLC to calculate and adjust the speed of the drives based on the true value of the surface ft./speed of the roller.
#3. Configure a roller slip fault routine for the PLC that tells when the wheels/encoder need cleaning.
#3. Do your best to design something that protects the wheels/encoder to prevent the spray from getting on them.
Yep. This is absolutely what I want to do. The problem is making it practical. Finding a way to lessen the overspray from getting to the encoder wheels on the rolls is Key.
Until then, I'm going back to controlling each drive with a potentiometer & a handheld tach for setup. Simplicity is sometimes the best option when technology is difficult to implement.