AivisJ
Posts: 5
Joined: Mon Dec 03, 2018 7:35 pm

Controlling 2 AC motors with power 2kW for each

Mon Dec 03, 2018 8:13 pm

Hello

I am very new for raspberry PI. But I have to make system where I can controll 2 AC motors. (220VAC)

I hope you can give me information about things what I need to do that.
The main idea is that both motors will start at same time, but the load and forces that brakes them could be different. When motors start to spin their torque have to be low, but then it must increase until predefined current reached and then cuts off. And I have to monitor current drawn by motors.

I have seen a video where it is done with dc motor and much lower power. (https://www.youtube.com/watch?v=_MCxxdKj5os)
I'm sorry couldn't find any video with raspberry PI! :(

So power for each of motor would be 2kW in my case. So I need much more things than DC setup.

For starting motors at the exact same time I could use motors with build-in encoders, right?
For controlling motors is there any other option without VFD?
What things I have to consider?
Maybe better 24 or 48 V DC motors? But then I need some transformator...

Once again, I am new for all this stuff, but I hope, that you could help me! Ask me questions I could try to answer them.

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Tage
Posts: 287
Joined: Fri May 24, 2013 2:29 am
Location: St Thomas, Ontario Canada

Re: Controlling 2 AC motors with power 2kW for each

Sat Dec 08, 2018 10:00 pm

you probably have found out that this forum is not the best place to get advice on this type of questions, but I can respond with my thoughts..
I would use two motor drives that are powered from single phase 230V and drive standard asynchronous three phase motors. I would not use dc motors, because I think that the cost of purchasing say a 4kW ac to dc converter that delivers 48Vdc to two 2kW dc motor drives plus motors will be too high.
My guess is that using standard 2kW three phase asynchronous motors and two 2kW ac drives is much less.

Depending on the application requirements, you may get away with using say 1.5kW drives, if you do not need to run full 2kW continuously.

pcmanbob
Posts: 6191
Joined: Fri May 31, 2013 9:28 pm
Location: Mansfield UK

Re: Controlling 2 AC motors with power 2kW for each

Sun Dec 09, 2018 12:25 pm

Controlling two 220VAC motors is no project for a beginner, to control that sort of power and rotating machinery you need to be qualified not only as an electrician but probably in electrical and mechanical design as well.

There are lots of things to consider in the design related to electrical safety and mechanical safety, not least that in the event of any component of the design failing the system must fail safe and stop everything safely.

I would never consider a pi a suitable device for controlling rotating machinery operating at these voltages because you can't predict how the pi would fail under all conditions.

Depending were you live there may also be legal ramifications with regard to what you want to do that could in the event of an accident, death or destruction of property, land you in trouble with the law.

For that reason I don't think you will find anyone with any sense willing to give you any detailed instructions on how to do such a project on this forum which after all is only a computer forum and not an electrical/mechanical design forum.
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AivisJ
Posts: 5
Joined: Mon Dec 03, 2018 7:35 pm

Re: Controlling 2 AC motors with power 2kW for each

Mon Mar 11, 2019 8:24 pm

Maybe, someone have worked with raspberry pi and VFD (variable frequency drive)? Is there any possibilitie to log information from vfd and show it on raspberry pi display?

blimpyway
Posts: 75
Joined: Mon Mar 19, 2018 1:18 pm

Re: Controlling 2 AC motors with power 2kW for each

Thu Mar 14, 2019 10:44 am

"controlling AC motor", without further details, can mean something as simple as turning the motor on/off or as complicated as precision motion control in CNC.

Unless you specify what you want to do with the motors no one can tell you how to do it.

AivisJ
Posts: 5
Joined: Mon Dec 03, 2018 7:35 pm

Re: Controlling 2 AC motors with power 2kW for each

Thu Mar 14, 2019 7:23 pm

All I need is that motors start in same time and reaches aprox. 450 rpm. Two motors - 2 vfd's.
Then load is being applied to motors, similar, but not equal. Till they stop or reach predefined current.
And Then I need to measure how torque increase and what is max value on each motor and compare them. And results show on display or even better Android phone/tablet.
Hope that you can understand what I want to say.

Brandon92
Posts: 773
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Controlling 2 AC motors with power 2kW for each

Thu Mar 14, 2019 7:39 pm

This sounds like a research or a school exercise.

However, did you buy the different parts for your setup. If so, can you share them. And what knowledge do you have about this subject?

And like the others says, safety is important and you need to apply all the required regulations ect. ect.

AivisJ
Posts: 5
Joined: Mon Dec 03, 2018 7:35 pm

Re: Controlling 2 AC motors with power 2kW for each

Thu Mar 14, 2019 8:39 pm

Right, it is for school 😁
At this moment there is nothing bought for this project. Have found some vfd's which I could use, at least which I think I could use.

Something like this https://m.aliexpress.com/item/328017301 ... 2595824041

And did some research - know that vfd must be with Rs485 interface, and raspberry pi must have Rs485 interface module

Brandon92
Posts: 773
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Controlling 2 AC motors with power 2kW for each

Thu Mar 14, 2019 8:56 pm

AivisJ wrote:
Thu Mar 14, 2019 8:39 pm
Right, it is for school
At this moment there is nothing bought for this project. Have found some vfd's which I could use, at least which I think I could use.
Okay, so I assume there is a teacher that would check your design if it save to use and that you connected everything correctly.

With that out of the way.
Is there a special reason to buy that controller from Alibaba and not from for example Siemens. And does your school have not those devices already.

And if you buy one from that side. It is important that you have all the documentation about it and also the protocol to talk to him.

And you need to choose a motor first before you can select the controller ect.

AivisJ
Posts: 5
Joined: Mon Dec 03, 2018 7:35 pm

Re: Controlling 2 AC motors with power 2kW for each

Thu Mar 14, 2019 9:17 pm

The final product, if everything will work, I will use in my workshop, so school haven't any interest to sponsor this project or give their devices.

For now I won't buy any parts from big brands, because I don't know if it will work - so alibaba or ebay 😁

About motor it could be something like this:
http://energostar.net/shop/6690/desc/mo ... 112m-8_opc

Brandon92
Posts: 773
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Controlling 2 AC motors with power 2kW for each

Tue Mar 19, 2019 2:02 pm

I had another thought about you setup. And I think it is not a good idea to use the over-current protection for this kind of application. I think you want you want to make something like a press? So maybe this is the kind of direction you need to go: Hydraulic System (Youtube) or the air variant of it.

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