Motor control

After doing littl bit of searching, I couldn't find the answers I needed, so hopefully someone could help clear this up for me.

I need to control a 3hp motor both forward and backwards.

A)I assume to do this will require 2 outputs from the PLC

B)What kinds of motor control do I need? Do I need a seperate on more or less wored in reverse for running it in reverse or (and I am sure there is) are there controllers out there that will do this for me

C) I'd like for it to be AB equipment, and also soft start/stop.


Any recomendations?

I am just trying to price out a ayatem before I dive into it all. Thanks in advance

If you want soft start/stop, you should look into an electronic reversing soft starter. AB makes these as well as many others. They will need your voltage, hp, and enclosure type to quote. They will also need to know if the load is very high inertia which would require a longer ramp up/down time and therefore a larger heatsink.

FOCUS said:

After doing littl bit of searching, I couldn't find the answers I needed, so hopefully someone could help clear this up for me.

I need to control a 3hp motor both forward and backwards.

A)I assume to do this will require 2 outputs from the PLC

B)What kinds of motor control do I need? Do I need a seperate on more or less wored in reverse for running it in reverse or (and I am sure there is) are there controllers out there that will do this for me

C) I'd like for it to be AB equipment, and also soft start/stop.


Any recomendations?

I am just trying to price out a ayatem before I dive into it all. Thanks in advance

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Just completed a Trolley car (3HP motor) running in both directions using a Powerflex 40 controlled over devicenet. Simple clean system, with no hassles.

Talk to your local AB distributor, they can help you spec out exactly what you need (they spec'd my system out for me, I just told them what I wanted it to be able to do).

MartB said:

Just completed a Trolley car (3HP motor) running in both directions using a Powerflex 40 controlled over devicenet. Simple clean system, with no hassles.

Talk to your local AB distributor, they can help you spec out exactly what you need (they spec'd my system out for me, I just told them what I wanted it to be able to do).

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As far as talking to an AB distributer about what I need:

I'm not a big fan of someone telling me what to get when they get a cut of it. I rather know what I need before asking for their help.

That's totally your choice, I guess I'm just lucky that I've got a distributor that is willing to help me, and that I can trust.

They've not let me down before and I know that they have the resources to make an informed descision for me.

I'm not a big fan of someone telling me what to get when they get a cut of it. I rather know what I need before asking for their help.

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I suppose that means you'd rather have someone you don't know tell you that you have appendicitis instead of a surgeon.

You're right that the salesman gets paid based on how much stuff he sells. However, he knows that the bulk of his business comes from repeat customers. If he sells you a bunch of stuff that you don't need you're not going to buy from him the next time you need something.

Ask the distributor's salesman to quote what you need and then post the parts list he proposes. You don't have to include prices, just hardware.

lol, funny story, a seargeon thought I was constipated when I had appendicitis.

It's not that I refuse to ask a distrivuter questions, but I refuse to go in there with no knowledge. I want to know what I am being sold, not told this is what I need. If someone I don't know (aka internet forums) can point me in the right direction, I can learn on my own and THEN procede to speak with a distributer. Going in blindly into anything is foolish, like going to a dealership to buy a car when you are a 15 year old amish boy. You need to have knowledge before making such a purchase.

In this horsepower range I would go with a PowerFlex 4 if you want to do simple discrete interface. The cost will be quite a bit less than a decent soft start and you get much more capability. A similarly rated PowerFlex 40 is about 30% higher priced than the PowerFlex 4, but you get more options and flexibility with the 40. Either option is much less than a soft start. Granted, these aren't aplles to apples comparisons so it really depends on your needs.

Keith

FOCUS said:

After doing littl bit of searching, I couldn't find the answers I needed, so hopefully someone could help clear this up for me.

I need to control a 3hp motor both forward and backwards.

A)I assume to do this will require 2 outputs from the PLC

B)What kinds of motor control do I need? Do I need a seperate on more or less wored in reverse for running it in reverse or (and I am sure there is) are there controllers out there that will do this for me

C) I'd like for it to be AB equipment, and also soft start/stop.

Any recomendations?

I am just trying to price out a ayatem before I dive into it all. Thanks in advance

Click to expand...

Your choice, you can use a drive or a reversing starter http://www.ab.com/industrialcontrols/products/nema_motor_control/contactors_starters_overload/505.html
Not knowing the application it would be hard to say which would offer the most for the money but using starters can still be viable.

With starters you would probably need at least 2 inputs, for the electrical interlocks and 2 outputs for forward/reverse. Depending on the situation you may need other inputs for limit of travel forward or reverse, this depends on the application.

If you feel you absolutely need soft start then a drive may be the best way to go, a slightly less expensive option may be the 160 drives AB also offers. http://www.ab.com/drives/ It depends on the plc, drive used, and setup how many I/O are used. There are numerous ways to use one.

The motor will be driving a pulley pulling a belt attatched to a maximum load of about 2,000lbs. The load itself will have 3 prox's for positioning.

How would you use the starters with the inputs? I don't know how this all works, sorry.

FOCUS said:

The motor will be driving a pulley pulling a belt attatched to a maximum load of about 2,000lbs. The load itself will have 3 prox's for positioning.

How would you use the starters with the inputs? I don't know how this all works, sorry.

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Well, what do you want to do with the inputs?
Drive a load until it sees a sensor come high?
Precision stops?
Stop in a general neighborhood?

If you don't know how it all works, & you are sold that you want AB, call your local AB rep & get to know him. Mine is very friendly & happy to assist in projects ranging from basic to extremely complicated. Develop a relationship with him, it will be worth it's weight in gold in the long run IMO.

drive load until high, essentially. but that has to do with the logic, not the motor control I would think..?

I plan on working with a distributer to help me figure things out, but I'd like to learn all I can before that point.

I get the impression that you may be in fairly deep water for your first time.


You have three separate problem groups here:

1) You need to write for yourself a description of the system operation, your control objectives, and the basic system components (motor, prox switches, HMI, PLC, starter, etc.)

2) You need to design your motor control system - solid state starter, reversing starter with contactors, VFD, etc. and pick those components.

3) You need to identify your automation components - I/O point list, PLC brand and model, etc.

If you are doing this for the first time, I strongly endorse the concept of talking to local distributors. If you are afraid of being "taken for a ride" then talk to three or more of them, take notes, and compare suggestions. If there is a big difference between them, do some research and then go back and ask.

Finally, in my experience the number of qualified, technically competent, and honest technical sales people overwhelmingly exceeds the number of snake oil salesmen. I've been in engineering for almost 40 years, and in that time I can remember few if any salesmen that I felt were out to cheat me. If you treat them honestly and with respect they will reciprocate.

Note that you have an obligation to them, too. Their time is valuable - it is their stock in trade. Don't waste their time, and respect the fact that their assistance to you is an investment they make in return for a reasonable opportunity to sell their products and services at a fair price. That means fair to them and to you.

FOCUS said:

The motor will be driving a pulley pulling a belt attatched to a maximum load of about 2,000lbs. The load itself will have 3 prox's for positioning.

How would you use the starters with the inputs? I don't know how this all works, sorry.

Click to expand...

Too bad you can not disclose what your money making applications may be but what you may want to do is hire someone with a little more experience then you have to assist during startup.

Since you are developing commercial products I would not worry whether its AB or not, most of the others may be just as well known.

For the application, you will probably need a drive and I would suggest showing a sales rep the specifications for the system and see what he says. You can always investigate his suggestions, the idea behind using sales reps etc is to use their knowledge of their products. Another thing about many sales reps etc is they want repeat business so will do what they can to make sure it works for you.

LOL, I can bet ya many engineers here at one time relied on their suppliers when they got started, as have many lowly techs like me.

I would say you definitely need a drive, possibly a servo, just depends on your positioning needs. With positioning required I would suggest an encoder be involved.

Lots of options, it all depends on the specific requirements.

I plan on hiring someone to do most of it, but like I said, I want to know what I am getting into before I dive in. It's just how I am. It's not that I am afraid of being taken for a ride, but I find that it is easier for people to discuss things if one of them is not a moron. Currently I am a moron and want to learn more before going any farther. I am not making any purchases until I understand all of the ins and outs, and all my options. I want to learn as much as I can before I move on to ask a distributer for information and pricing. I already know my I/O requirements (for the most part) and what I need everything to do. I am just trying to take the leap between robotic design and programming (I have built and programmed small robotics for 6 years) where I program in C and Basic, and have all PWM outputs to motor controllers. Much use of hall effect sensors, prox'es, light gates, vision systems, etc.. .I just need a translation to PLC terminology and what differences I need to be aware of. I understand the high level overview of control systems, just not the details involving industrial applications and conventions.

The reason I like to stay with AB products is becuase I know a lot of facilites stock spare AB parts. At least most of the firms I have worked for have.

As far as getting more info about what I am doing, well, there are legal complications right now. I will know soon if I can disclose more. I really wish I could.

Thanks for the help all!